CA2170853A1 - Method of recalibrating electronic scales - Google Patents
Method of recalibrating electronic scalesInfo
- Publication number
- CA2170853A1 CA2170853A1 CA 2170853 CA2170853A CA2170853A1 CA 2170853 A1 CA2170853 A1 CA 2170853A1 CA 2170853 CA2170853 CA 2170853 CA 2170853 A CA2170853 A CA 2170853A CA 2170853 A1 CA2170853 A1 CA 2170853A1
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- scale
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- 238000000034 method Methods 0.000 title claims abstract description 42
- 238000009434 installation Methods 0.000 claims abstract description 77
- 230000015654 memory Effects 0.000 claims abstract description 26
- 238000005259 measurement Methods 0.000 claims abstract description 13
- 230000000694 effects Effects 0.000 claims abstract description 10
- 230000002411 adverse Effects 0.000 claims abstract description 7
- 238000013479 data entry Methods 0.000 claims description 9
- 230000005484 gravity Effects 0.000 abstract description 10
- 238000005303 weighing Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 5
- 230000007246 mechanism Effects 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000003936 working memory Effects 0.000 description 3
- 238000012937 correction Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004913 activation Effects 0.000 description 1
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- 230000002950 deficient Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000010338 mechanical breakdown Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000000135 prohibitive effect Effects 0.000 description 1
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- 230000003252 repetitive effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G23/00—Auxiliary devices for weighing apparatus
- G01G23/01—Testing or calibrating of weighing apparatus
- G01G23/015—Testing or calibrating of weighing apparatus by adjusting to the local gravitational acceleration
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Devices For Checking Fares Or Tickets At Control Points (AREA)
Abstract
A method of recalibrating an electronic scale is disclosed which causes the scale to indicate accurate weight measurements regardless of variations in the relative magnitude of the force of gravity under which the scale is operating between a site of origin where it is calibrated, and a site of installation which tend to adversely effect accurate weight. The method utilizes the known principles of gravity that it varies from place to place as afunction of elevation above sea level and proximity to the equator. Certain data relating to the effect on the accuracy of the scale due to variations in the gravitational force between a site of origin and a site of installation is placed in memory in the scale at a site of origin, where the scale is initially calibrated. When corresponding data indicative of the variation in the magnitude of gravitational force at the site of installation is then entered into the scale, the microprocessor of the scale adjusts the factory calibration to compensate for the difference in the magnitude of the force of gravity so that the digital readout of the scale indicates accurate weight for mail pieces placed thereon at the site of installation.
Description
METHOD OF RECALIBRATING ELECTRONIC SCALES
Background of the Invention The present invention relates generally to the field of electronic weighing scales, and more particularly to a method for recalibrating such scales to compensate for possible adverse effects on the accuracy of the scales from variations in physical and/or environmental conditions under which they operate, particularly the force of gravity.
This invention is an improvement on the inventions disclosed and claimed in prior copending applications Serial Nos. 165,151 and 165,152, filed December 10,1993, in the names of Gerald C. Freeman and Paul C.
Talmadge, and copending application Serial No. 364,168, filed December 12,1994, in the names of Gerald C. Freeman, Konstantin G. Kodonas and Paul C. Talmadge, all assigned to the assignee of this application. This application is also related to copending application Serial No. 364,169, filed on December 12, 1994, in the name of Gerald C. Freeman, and assigned to the assignee of this application, and which discloses and claims an electronic scale of the type with which the recalibrating method disclosed and claimed in this application may be practiced.
Since their introduction, electronic scales have become widely accepted in many weighing applications for a number of reasons, primarily the extreme degree of accuracy with which the scales can weigh articles, the wide range of weights the scales are capable of handling and the ease and convenience of digital display readout of the weight of an article. Electronic scales are now used almost exclusively in such high volume utility situations as mail, parcels, bulk food and dry goods sold by weight measure, air terminal baggage, and other situations where highly accurate weight is required on a repetitive basis with minimum recovery time between individual weighings.
In recent years, electronic scales have become almost the universal standard in connection with weighing mail and parcels, and it is in connection with this utility that the present invention was developed, although the utility of the present invention is not limited to this use. Perhaps the primary contributing factor to the popularity of electronic scales in the postal field is the high degree of accuracy inherent in such scales. When one considers the billions of mail pieces weighed annually by the U. S.
Postal Service in the course of handling mail, and the millions of packages and parcels also handled not only by the Postal Service but also by all of the courier services which compete with the Postal Service, one can begin to appreciate the vast amount of money by which customers may be overcharged or undercharged depending on whether scales are overweighing or underweighing, in the course of dispatching all of this mail and parcels if the scales which determine the mail and parcel postage amount are not highly accurate.
For example, a generally accepted standard of accuracy among major electronic scale manufacturers is that they be within .03% to .05% of full scale. If we assume a 100 pound scale, the required accuracy becomes .03 to .05 pounds, or .48 to .80 ounces, over the range of the scale. Thus, it is apparent that electronic scales are capable of weighing accurately to an impressive less than one ounce in 100 pounds. Correspondingly, a one pound letter scale can weigh letter mail accurately to within less than one one hundredth of an ounce.
Aside from an inherent desire to provide highly accurate scales for monetary purposes described above, a major factor contributing to this high degree of accuracy is the requirement by the National Bureau of Weights and Measures that a scale be capable of weighing within the above limits of accuracy in order to be approved for commercial use in mail and parcel applications. Although many customers in other applications may not require this degree of accuracy, customers in the mail and parcel fields will not purchase scales that do not have National Bureau of Weights and Measures approval.
A major problem that occurs with electronic load cell scales is that the accuracy of the scales can be adversely affected by variations in certain physical and/or environmental conditions under which the scales are required to operate, many of which are discussed in detail in the aforementioned applications. In the first two of these applications, the problems associated with maintaining the accuracy of the scale under different operating conditions were addressed by providing an apparatus and method for recalibrating an electronic scale in which an auxiliary weight, which is constant although not necessarily precisely known, is mounted in the scale so as to be movable between a first position in which the weight is supported by a portion of the main frame of the scale, and a second position in which the weight is supported by the platter of the scale on which the item to be weighed is placed. A motor drives an eccentric mechanism which raises and lowers the auxiliary weight, either on demand to place the weight on the scale platter when the operator desires to recalibrate the scale, or automatically in response to activation of various control elements caused by various external influences, such as periodically, whenever the scale is powered up, or when it senses a change in physical or atmospheric conditions.
The major disadvantage of this apparatus and method is the need for providing the auxiliary weight device and the electric and electronic control means for periodically placing the auxiliary weight on the scale platter in order to recalibrate the scale. The advantage of having this internal auxiliary weight mechanism is entirely lost in a small capacity scale, such as the one described hereinafter, where the cost of providing the auxiliary weight mechanism and control means therefore would be entirely prohibitive in a small capacity scale. Thus, the third of the above mentioned applications discloses and claims an improvement to the two previous applications in which the motorized mechanism by which the auxiliary weight was added to the scale platter at the appropriate times is eliminated. In the scale disclosedin that application, the scale platter is readily removable from the scale, and is, therefore, used as the recalibrating weight, providing the actual weight of the platter remains constant at both the site of origin and the site of installation. Without the motorized recalibrating weight mechanism, it was possible to produce a relatively small scale having a low weight range in the order of 5 to 10 pounds, which was highly reliable and less prone to mechanical breakdown, both factors tending make the new scale more economically attractive and competitive than the prior scale. However, notwithstanding these advantages, the disadvantage still remained, that the recalibration process required a relatively complex series of steps to initiallycalibrate the scale at the site of origin and then recalibrate it at the site ofinstallation. Thus, there is a need for a method of recalibrating an electronic scale which does not require that an auxiliary weight be added to the scale at the site of installation, whether it be a built in weight that is added to the scale platter as in the first two of the above mentioned applications, or a removable scale platter, as in the last of those applications, and which therefore requires fewer steps to carry out the entire process of calibrating and recalibrating the scale.
Brief Summary of the Invention The present invention satisfies the foregoing need and at least obviates if not eliminates all of the problems discussed above relating to the accuracy of electronic scales. And while the invention is disclosed herein as 21 708~i3 being practiced in conjunction with the same apparatus as that disclosed above and disclosed and claimed in the third and fourth of the aforementioned copending applications, it nevertheless can be practiced apart from that particular apparatus, and therefore has separate and unique utility in the art.
We have discovered that an electronic scale can be recalibrated in the field to compensate for variations in the accuracy of the scale caused by the force of gravity by utilizing the known principles of gravity that the relative magnitude thereof can be determined at any point on the earth, and that it remains constant at that point. Since the force of gravity varies from place to place around the world, depending on the proximity of a given plate to the equator, a scale properly calibrated at the factory in Connecticut may not be accurate within the desired limits in Florida. Also, the effect of gravity varies with height, so that a scale calibrated properly at sea level will not be accurate within the desired limits in Denver, Colorado. Thus, by determining the relative magnitude of the force of gravity at various locations in a predetermined geographic area, and assigning electronic correction factors in the microprocessor of the scale corresponding to those locations, it becomes possible to electronically recalibrate the scale by applying appropriate correction factors to the factory calibration of the scale depending on where the scale is ultimately.
Thus, the present invention is a method of recalibrating an electronic scale to indicate accurate weight measurements of articles placed on the scale regardless of variations in the force of gravity under which the scale is operating between a site of origin and a site of installation and which tend to adversely affect accurate weight. The method is typically practiced in conjunction with an electronic scale which has a load cell capable of producing an analog voltage output signal indicative of the weight of an article placed on the scale, an analog to digital converter for converting the analog voltage output signal from the load cell into digital information representing the analog output, a digital readout for displaying the weight of the article, and a microprocessor for converting the digital representation of the analog output of the load cell into information for driving the digital readout to cause it to display desired information.
In its broader aspects the method comprises the steps of generating first data relating to the effect on the accuracy of said scale due to variations in the relative magnitude of the gravitational force between a site of origin and a site of installation, at the site of origin placing the first data into the memory of a microprocessor in the scale, determining an electronic count 21708~3 differential between the scale with 0# weight on the platter and with a known weight thereon and placing the first electronic count differential into a memory to calibrate the scale for accurate weight measurement at the site of origin. The method further includes the steps of removing the scale from the site of origin to a site of installation at which the scale may operate under a gravitationa! force different from that which prevailed at the site of origin, and entering second data into the microprocessor relating to the relative magnitude of the gravitational force at the site of installation which causes the microprocessor to adjust the factory calibration to compensate for any variation in the gravitational force between the site of origin and the site installation, whereby the scale is recalibrated at the site of installation to cause the scale to indicate accurate weight measurements regardless of any variation in the gravitational force between the site of origin and the site of installation.
In some of its more limited aspects, the step of generating the first data includes the steps of assigning separate identifiers to the site of origin and the site of installation which are indicative of the relative magnitudes of the gravitational force at the site of origin and the site of installation respectively, and ascertaining an arithmetic multiplier for each of the magnitudes of gravitational force that will adjust the factory calibration of the scale to compensate for a difference in the gravitational force between that at the site of origin and that at the site of installation. Further, with the scale at a site of origin, the step of placing the first data into the memory of a microprocessor includes the step of placing the identifiers and the corresponding arithmetic multipliers into the memory of the microprocessor. Subsequently, with the scale at the site of installation, the step of entering the second data includesthe step of entering the identifier into the scale that corresponds to the site of installation of the scale, whereby the identifier causes the corresponding arithmetic multiplier to adjust the electronic count differential by the amount of the arithmetic multiplier to readjust the electronic count differential to compensate for the difference in the magnitude of gravitational force between the site of origin and the site of installation.
In a presently preferred mode of carrying out the invention, the geographic locations correspond to the locations identified by postal zone codes applicable to the predetermined geographic area in which the geographic locations are situated, which, at least in the case of the United States and Canada, can be conveniently represented by the first three digits of postal ZIP codes, although other forms of geographic location code systems could be effectively utilized, such as the telephone number area 21708~3 code system. Further, in one embodiment of the invention, the step of entering the identifier into the scale that corresponds to the geographic location of the site of installation comprises the step of manually entering theidentifier through a data entry component of the scale. In other embodiments, this step is carried out by inserting a PROM into the scale which contains either the identifier or the appropriate representation of a ZIP
or other geographic location code.
Having briefly described the general nature of the present invention, it is a principal object thereof to provide a method of recalibrating an electronicscale to indicate accurate weight measurements of articles placed on the scale regardless of variations in the relative magnitude of gravitational force under which the scale operates between a site of origin and a site of installation and which tend to adversely affect accurate weight.
Another object of the present invention is to provide a method of recalibrating an electronic scale according to the preceding object which does not require that an auxiliary weight be added to the platter of the scale in order to achieve a recalibration, thereby avoiding the expense of providing either a built in auxiliary weight that must be periodically added to the weight of the platter, or going through a complex series of steps as required with using a removable platter in lieu of an auxiliary weight.
These and other objects, advantages and features of the method of the present invention will become more apparent from an understanding of the following detailed description of a preferred embodiment of the invention when considered in conjunction with the accompanying drawings.
Description of the Drawings FIG. 1 is an exploded, perspective view of the major components of a representative electronic scale with which the method of the present invention is practiced.
FIG. 2 is a chart representing the relationship between all United States ZIP codes and corresponding identifiers which are indicative of the relative magnitude of gravitational force of the locations identified by the ZIPcodes.
FIG. 3 is a chart representing the relationship between the identifiers shown in Fig. 2 and arithmetic multipliers by which an electronic count differential in memory in the scale is adjusted to compensate for variations in the relative magnitude of gravitational force between the site of origin and the site of installation.
FIG. 4 is a relatively simple schematic of the principal control components of an electronic scale required for the practice of the present invention.
FIG. 5 is a view similar to Fig. 4 illustrating another embodiment of the practice of the present invention.
Detailed Description of the Invention Referring now to the drawings, and more particularly to Fig. 1 thereof, the major components of a representative scale with which the present invention is practiced are shown in an exploded manner, and are seen to comprise a housing, indicated generally by the reference numeral 10, a load cell, indicated generally by the reference numeral 12, a weight distribution plate, indicated generally by the reference numeral 14, a top cover, indicated generally by the reference numeral 16, and finally a platter, indicated generally by the reference numeral 18, on which the mail piece to be weighed is placed.
The housing 10 is generally rectangular and has oppositely disposed upstanding side walls 20, an upstanding rear wall 22, a very short, upstanding front wall 24, and a bottom wall 26 to which the side, rear and front walls are connected. A plurality of feet 28 are suitably connected to the underside of the bottom wall 26 in recesses defined by bosses 30 for supporting the scale. The housing 10, as well as the top cover 16 and the platter 18, are formed of injection molded polycarbonate blend plastic. An upstanding wall 32 extends across the housing 10 between the side walls 20 to divide the space within the base and housing 10 into forward and rearward compartments 34 and 36, the former for the electronic components which are actuated by a plurality of push buttons that extend through suitable openings 38 formed in the top cover 16, the latter for the load cell 12 and other electronic components that will not fit in the forward compartment 34.
A metal support plate 40 is suitably secured to the bottom wall 26 for supporting the fixed end 42 of the load cell 12, which is positioned on the support plate 40 and is connected to the housing 10 by suitable screws 44 which pass through openings in the bottom wall 26 and the support plate 40 and threadedly engage the fixed end 42 of the load cell 12. The opposite or free end 46 of the load cell 12 is connected to the weight distribution plate 14by means of similar screws 48 which pass through openings in the plate 14 and are threadedly engaged with the free end 46 of the load cell 12.
2I 7~ 853 The top cover 16 is dimensioned to overlie the housing 10, and includes a push button access portion 50 which includes the aforementioned button access openings 38 and overlies the forward compartment 34 in the housing 10. The remainder of the top cover 16 is a generally rectangular portion 52 which overlies the rearward compartment 36 in the housing 10. A
pair of screws 54 suitably connect the rectangular portion 52 of the top cover 16 to the upper ends 56 of a pair of posts 58 to secure the top plate 16 to the housing 10.
The scale platter 18 is basically a generally rectangular body member 60 which has approximately the same dimensions as the rectangular portion 52 of the top cover, and is provided with four identical legs 62, only two of which are shown in Fig.1. Each leg 62 extends through one of the openings 64 in the weight distribution plate 16 and seats firstly in the apertures 66 of one of a plurality of grommets 68 which in turn fit into suitable recesses 70 formed adjacent the four corners of the weight distribution plate 14. The legs 62 are gripped by the inner edges of the apertures 66 with sufficient strength to firmly retain the platter 18 on the weight distribution plate 14, but not so tightly that it cannot be readily removed by a user simply by lifting the platter upwardly. It should be noted that the openings 64 in the top cover 16 are sufficiently large to enable the legs 62 to pass freely therethrough without touching the inner edges of the apertures 66 so that the platter 18 is supported solely by the weight distribution plate 14, which, as described above, is in turn supported solely by the load cell 12.
It should be understood that the foregoing scale has been shown and described simply for the purpose of illustrating a type of electronic scale withwhich the present invention can be practiced, and that other scales having different forms of construction could be utilized.
Coming now to a detailed description of the method of the present invention, it will be seen that the invention, in its broader aspects, comprisesa series of steps directed toward generating certain data relating to the effecton the accuracy of the scale due to variations in the relative magnitude of the gravitational force between a site of origin and a site of installation, which data is later used when additional data is entered into the scale at a site of installation. It is possible that some of this data pre-exists, in which case itcan be utilized in the practice of the invention; if not, it must be ascertained.
In its more limited aspects, the invention also includes a series of steps that are carried out to generate the aforementioined data, and other steps are carried out in connection with how the additional data is entered into the scale. In order to facilitate a clear understanding of the invention, the 21 7l~853 g complete series of steps will be described in the sequence in which they are carried out in the most limited aspect of the invention, with the understanding that the breadth of the invention is not intended to be limited by this form of description, but rather only by reference to the claims appended hereto.
Assuming for the sake of this description that none of the necessary information already exists, and with reference to Fig. 2, the first step in the practice of the invention is to identify a predetermined number of geographic locations within a predetermined geographic area. This involves first making a determination of the geographic area, which may be the entire world or any portion thereof. For convenience of illustration, the predetermined geographic area is the United States, and the selected geographic locations are the areas within the United States identified by the first three digits of postal ZIP codes. As is well known, the U. S. Postal Service has established a zone system for the country in which postage rates between any two given zones are established for a given base weight. Also, all ZIP codes in the country are identified as being distributed among these zones. Thus, if one knows the ZIP code of the destination of a parcel, he can determine the postal zone for that destination, from which he can determine the rate per base weight, and by applying this to the weight of the parcel he determines the amount of postage required. It should also be understood that additional locations could be included, such as Europe, and additional geographic locations could be identified, again using postal zone codes for convenience, but other location codes, such as the aforementioned telephone area codes, could be utilized. The two letter state abbreviation system adopted by the U. S. Postal Service could also be utilized, and any of these systems could be utilized alone or in combination with other systems.
Thus, in the case illustrated in Fig. 2, it will be seen that all of the ZIP
codes in the United States have been listed in the first three digit format, buthave been grouped in a predetermined manner by closely adjacent ZIP
codes simply to reduce the number of geographic locations which must be identified. Column A shows a representative listing of ZIP codes in such groups, commencing with the lowest number existing ZIP code and ending with the highest number existing ZIP code.
The next step is to ascertain the relative magnitude of gravitational force for each of the geographic locations within the predetermined geographic area. This information generally exists and is available in some form for various parts of the world, but if a specific geographic location to becovered in the practice of the invention is one for which this information is not available, it must then be ascertained.
2~ 70853 Once the relative magnitude of gravitational force for all of the geographic locations has been ascertained, an arbitrary identifier is assigned to each of the geographic locations that is indicative of the relative magnitude of the gravitational force at each of these locations. As seen in Column B of Fig. 2, the identifiers, listed in Column B, are two digit numbers, although other forms of alpha or numeric designations could be used. Two digit numbers, assigned in random order, are preferred for security reasons so that owners of the scales cannot ascertain the identifiers for geographic locations other than the location at which the scale is installed. This prevents them from improperly recalibrating the scale to indicate a lower weight than the actual weight of a mail piece at the site of installation of thescale and consequently paying insufficient postage for that mail piece.
It will be seen from Fig. 2 that the same identifier is assigned to more than one geographic location for the reason that there are a large number of ZIP code areas in the United States where the gravitational force is the same. It should be understood, as previously mentioned, that the magnitude of gravitational force for any location is a function of the elevation of that location relative to sea level and the proximity of it to the equator. More particularly, the higher a point is above sea level, the lower is the gravitational force since it is further from the center of the earth. Similarly,the closer a point is to the equator, the less is the gravitational force due tocentrifugal force caused by the rotation of the earth which negatively affects gravitational force. Thus, a ZIP code in Boulder, Colorado, at an elevation of 5,000 feet, may have the same gravitational force as a ZIP code in San Diego, California at sea lev~' because the closer proximity of sea level Miami to the equator offsets the 5,000 foot elevation of Boulder, even though Denver i_ considerably farther from the equator than San Diego.
The next step is that of ascertaining an arithmetic multiplier for each of the different magnitudes of gravitational force that will adjust the factory calibration of the scale to compensate for a difference in the gravitational force between that at the site of origin of the scale, typically the factory, and that at the site of installation. Thus, with reference to Fig. 3, it will be seen that each of the gravitational identifiers listed in Column A has a corresponding arithmetic multiplier listed in Column B. How these multipliers work to recalibrate the scale at the site of installation will be fully explained below. However, it should be noted here that if a scale is installed at a location that has the same relative magnitude of gravitational force as that which exists at the site of origin of the scale, it is not necessary to recalibrate the scale since the factory calibration will suffice to cause the scale to provide accurate weight measurements at the site of installation.
Therefore, assuming that the identifier at the site of origin is #41, the corresponding multiplier for all ZIP codes having that gravitational force will be 1.000. Again for the sake of illustration, it has been assumed that the difference in the relative magnitude of gravitational force between the geographic locations identified by the gravitational identifiers 0.0005.
It should be noted at this point that the two previous steps, i.e., assigning an identifier to each geographic location and ascertaining an arithmetic multiplier, have been collectively designated, in a broader aspect of the invention, as generating first data relating to the effect on the accuracy of the scale due to variations in the relative magnitude of gravitational force between the site of origin and the site of installation, and in a slightly more limited aspect of the invention, as generating first data relating to the effecton the accuracy of the scale due to variations in the relative magnitude of gravitational force between all of the geographic locations.
The next step is to place the identifiers and the corresponding arithmetic multipliers, or the first data as the case may be, depending on whether one is considering the most limited aspect of the invention or one of the broader aspects as described above, into the memory of a microprocessor in the scale. Thus, with reference to the schematic diagram of Fig. 4, it will be seen that the scale includes a microprocessor 80 which includes several memory registers, one of which 82 is for permanent storage of the identifiers listed in Column A of Fig. 3. Another memory register 84 is for permanent storage of the multipliers listed in Column B of Fig. 3. This step is performed at the site of origin and is part of the general software installation for the scale.
The next step is to determine an electronic count differential between the scale with 0# weight on the platter and with a known weight on the platter, and placing the electronic count differential into a memory in the microprocessor to calibrate the scale for accurate weight measurement at the site of origin. The determination of the electronic count differential itself involves three successive steps, which commences with determining a raw electronic count of the scale with 0# weight on the platter which, by way of an example, might be 21,200. This is accomplished by the load cell 12 generating an analog voltage indicative of the weight of the empty platter 18.
Basically, a load cell, as seen in Fig. 1, using strain gage technology can be a generally rectangular metallic body member which is adapted to have one end 42 thereof rigidly mounted on a frame so that the load cell 12 is supported only at that end, with the rest of the body member being 21 708a3 cantilevered from the mounting end. The other end 46 of the body member is provided with some means for supporting a weight, such as the weight distribution plate 14 and the platter 18. Strain gages are mounted on the body member in appropriate locations that stretch very slightly when the body member is deflected by the application of the weight. An electric voltage is applied across the strain gage, the output of which varies in accordance with the extent to which the strip is strained by weight imposed on the free end of the body member. Referring to Fig. 4, the output load cell voltage is amplified by the amplifier 86 and applied to an analog to digital converter 88 which converts the analog voltage into a digital signal which can be recognized by a microprocessor 80 for further processing. In a manner known in microprocessor technology, the details of which are not necessary to an understanding of the invention, the microprocessor 80 converts the digital signal into a predetermined electronic count, which is transferred to and temporarily stored in a working memory register 90.
A known weight is then placed on the platter 18, which typically weighs approximately the same as the weight capacity of the scale, which in the scale disclosed herein is 5 pounds. A raw electronic count of the scale with the known weight on the platter 18 is then determined in the same manner as just described for determining and storing the raw electronic count of the scale with 0# weight on the platter 18, which, again by way of example, might be 1 10,100, and this count is also placed in the working memory register 90.
Again in known manner in microprocessor technology, the microprocessor accesses the two raw electronic counts in the working memory register 90 and subtracts the first count from the second count to determine a first electronic count differential, which in the example being given, is 88,900, and which represents the counts per known weight at the site of origin. This electronic count differential is then placed in a permanentmemory register 92.
The scale is then removed from the site of origin to the site of installation at one of the geographic locations at which the scale may operate under a gravitational force different from that which prevailed at the site of origin. At the site of installation, when the scale is first powered up, it prompts the operator to enter the identifier into the scale that corresponds to the geographic location of the site of installation, which he obtains from a chart supplied with the scale which, in the manner shown in abbreviated version in Fig. 2, lists the identifiers for all of the ZIP groups for the country.
This is accomplished most conveniently by utilizing the data entry keypad 94 of the scale which is also used to enter other information pertinent to determining the amount of postage required for the mail piece being weighed, such as the class of mail or a ZIP to Zone and special fees conversion factor in the case of a parcel, although some other form of data entry device could be utilized. The keypad 94 transmits this information to the identifier memory register 82 of the microprocessor, where, in a manner known in microprocessor technology, the corresponding identifier stored in the memory register 82 is accessed and transferred to the multiplier memory register 84. This in turn accesses the appropriate multiplier for the identifierjust accessed from the identifier memory register 82, and this multiplier is transferred to the storage memory 92 which contains the electronic count differential determined at the site of origin. The electronic count differential is then adjusted by the product of the multiplier and the electronic count differential to establish a new electronic count differential for the scale to compensate for the difference in the relative magnitude of gravitational force between the site of origin and the site of installation. In the example stated above, if it is assumed that the site of origin is Connecticut, and the site of installation is Boulder, Colorado, and that the identifier for Boulder is 76, then from Fig. 3, the new arithmetic multiplier is .9995, and the new electronic count differential for the scale in Boulder is 88,900 times .9995, or88.885.5. Thus, when an article is now placed on the scale, the accurate weight thereof will appear on the digital display 96.
Fig. 5 illustrates another embodiment of the invention in which the appropriate multiplier for the electronic count differential is selected by an identifier which in turn is selected by a ZIP code entered into the scale via a PROM. Although the above described ZIP code information is readily available on charts supplied with less sophisticated scales, most electronic scales are provided with software which includes the ZIP to ZONE
conversion information in the form of a ZIP to ZONE PROM, which is supplied with the scale. Thus, it will be apparent that if the ZIP code information shown in Fig. 2 is placed in memory in the microprocessor, as in the memory register 98 shown in Fig. 5, at the site of origin, and an appropriate PROM, as indicated by the box labeled 100 in Fig. 5, is inserted into the scale, either at the site of origin if the site of installation is then known, or at the site of installation itself, the site of installation ZIP code on the PROM will, again in a manner well known in microprocessor technology, access the appropriate ZIP code stored in the memory register 98 which, in turn, accesses the corresponding identifier from the memory register 82. The identifier then accesses the corresponding multiplier from the memory register 84, and the recalibration process described above can then take place.
One disadvantage of the embodiment just described is that it requires a substantially large capacity memory in the scale in order to store all of the ZIP code groups listed on the actual ZIP to identifier chart, and this tends to increase the cost of the scale. This disadvantage is overcome in another embodiment of the invention, which is a modification of that shown in Fig. 4, in which the appropriate identifier contained in the memory register 82 is accessed by entering the identifier for the site of installation through a PROM
which includes the identifier for the site of installation of the scale, rather than through the data entry keypad 94. This requires a further step in the overall process, that of placing the identifier in a PROM at the time that the ZIP code information for a particuiar scale is programmed into the PROM. Thus, if the PROM is already in the scale when it is first powered up at the site of installation, a recalibration will take place instantly.
In a still further embodiment of the invention, it is possible to enter the ZIP code of the site of installation through a data entry keypad in the same manner as the identifier was entered in the previously described embodiment illustrated in Fig. 4. The advantage of this is that the scale can be recalibrated at the site of installation in the event that the PROM is missing or defective when the scale is first powered up at the site of installation.
It is to be understood that the method of the present invention are not to be considered as limited to the practice of the specific steps described above, which are merely illustrative of the best mode presently contemplated for carrying out the method of the invention and which are susceptible to such changes as may be obvious to one skilled in the art, but rather they are intended to cover all such variations, modifications and equivalents thereof as may be deemed to be within the scope of the claims appended hereto.
Background of the Invention The present invention relates generally to the field of electronic weighing scales, and more particularly to a method for recalibrating such scales to compensate for possible adverse effects on the accuracy of the scales from variations in physical and/or environmental conditions under which they operate, particularly the force of gravity.
This invention is an improvement on the inventions disclosed and claimed in prior copending applications Serial Nos. 165,151 and 165,152, filed December 10,1993, in the names of Gerald C. Freeman and Paul C.
Talmadge, and copending application Serial No. 364,168, filed December 12,1994, in the names of Gerald C. Freeman, Konstantin G. Kodonas and Paul C. Talmadge, all assigned to the assignee of this application. This application is also related to copending application Serial No. 364,169, filed on December 12, 1994, in the name of Gerald C. Freeman, and assigned to the assignee of this application, and which discloses and claims an electronic scale of the type with which the recalibrating method disclosed and claimed in this application may be practiced.
Since their introduction, electronic scales have become widely accepted in many weighing applications for a number of reasons, primarily the extreme degree of accuracy with which the scales can weigh articles, the wide range of weights the scales are capable of handling and the ease and convenience of digital display readout of the weight of an article. Electronic scales are now used almost exclusively in such high volume utility situations as mail, parcels, bulk food and dry goods sold by weight measure, air terminal baggage, and other situations where highly accurate weight is required on a repetitive basis with minimum recovery time between individual weighings.
In recent years, electronic scales have become almost the universal standard in connection with weighing mail and parcels, and it is in connection with this utility that the present invention was developed, although the utility of the present invention is not limited to this use. Perhaps the primary contributing factor to the popularity of electronic scales in the postal field is the high degree of accuracy inherent in such scales. When one considers the billions of mail pieces weighed annually by the U. S.
Postal Service in the course of handling mail, and the millions of packages and parcels also handled not only by the Postal Service but also by all of the courier services which compete with the Postal Service, one can begin to appreciate the vast amount of money by which customers may be overcharged or undercharged depending on whether scales are overweighing or underweighing, in the course of dispatching all of this mail and parcels if the scales which determine the mail and parcel postage amount are not highly accurate.
For example, a generally accepted standard of accuracy among major electronic scale manufacturers is that they be within .03% to .05% of full scale. If we assume a 100 pound scale, the required accuracy becomes .03 to .05 pounds, or .48 to .80 ounces, over the range of the scale. Thus, it is apparent that electronic scales are capable of weighing accurately to an impressive less than one ounce in 100 pounds. Correspondingly, a one pound letter scale can weigh letter mail accurately to within less than one one hundredth of an ounce.
Aside from an inherent desire to provide highly accurate scales for monetary purposes described above, a major factor contributing to this high degree of accuracy is the requirement by the National Bureau of Weights and Measures that a scale be capable of weighing within the above limits of accuracy in order to be approved for commercial use in mail and parcel applications. Although many customers in other applications may not require this degree of accuracy, customers in the mail and parcel fields will not purchase scales that do not have National Bureau of Weights and Measures approval.
A major problem that occurs with electronic load cell scales is that the accuracy of the scales can be adversely affected by variations in certain physical and/or environmental conditions under which the scales are required to operate, many of which are discussed in detail in the aforementioned applications. In the first two of these applications, the problems associated with maintaining the accuracy of the scale under different operating conditions were addressed by providing an apparatus and method for recalibrating an electronic scale in which an auxiliary weight, which is constant although not necessarily precisely known, is mounted in the scale so as to be movable between a first position in which the weight is supported by a portion of the main frame of the scale, and a second position in which the weight is supported by the platter of the scale on which the item to be weighed is placed. A motor drives an eccentric mechanism which raises and lowers the auxiliary weight, either on demand to place the weight on the scale platter when the operator desires to recalibrate the scale, or automatically in response to activation of various control elements caused by various external influences, such as periodically, whenever the scale is powered up, or when it senses a change in physical or atmospheric conditions.
The major disadvantage of this apparatus and method is the need for providing the auxiliary weight device and the electric and electronic control means for periodically placing the auxiliary weight on the scale platter in order to recalibrate the scale. The advantage of having this internal auxiliary weight mechanism is entirely lost in a small capacity scale, such as the one described hereinafter, where the cost of providing the auxiliary weight mechanism and control means therefore would be entirely prohibitive in a small capacity scale. Thus, the third of the above mentioned applications discloses and claims an improvement to the two previous applications in which the motorized mechanism by which the auxiliary weight was added to the scale platter at the appropriate times is eliminated. In the scale disclosedin that application, the scale platter is readily removable from the scale, and is, therefore, used as the recalibrating weight, providing the actual weight of the platter remains constant at both the site of origin and the site of installation. Without the motorized recalibrating weight mechanism, it was possible to produce a relatively small scale having a low weight range in the order of 5 to 10 pounds, which was highly reliable and less prone to mechanical breakdown, both factors tending make the new scale more economically attractive and competitive than the prior scale. However, notwithstanding these advantages, the disadvantage still remained, that the recalibration process required a relatively complex series of steps to initiallycalibrate the scale at the site of origin and then recalibrate it at the site ofinstallation. Thus, there is a need for a method of recalibrating an electronic scale which does not require that an auxiliary weight be added to the scale at the site of installation, whether it be a built in weight that is added to the scale platter as in the first two of the above mentioned applications, or a removable scale platter, as in the last of those applications, and which therefore requires fewer steps to carry out the entire process of calibrating and recalibrating the scale.
Brief Summary of the Invention The present invention satisfies the foregoing need and at least obviates if not eliminates all of the problems discussed above relating to the accuracy of electronic scales. And while the invention is disclosed herein as 21 708~i3 being practiced in conjunction with the same apparatus as that disclosed above and disclosed and claimed in the third and fourth of the aforementioned copending applications, it nevertheless can be practiced apart from that particular apparatus, and therefore has separate and unique utility in the art.
We have discovered that an electronic scale can be recalibrated in the field to compensate for variations in the accuracy of the scale caused by the force of gravity by utilizing the known principles of gravity that the relative magnitude thereof can be determined at any point on the earth, and that it remains constant at that point. Since the force of gravity varies from place to place around the world, depending on the proximity of a given plate to the equator, a scale properly calibrated at the factory in Connecticut may not be accurate within the desired limits in Florida. Also, the effect of gravity varies with height, so that a scale calibrated properly at sea level will not be accurate within the desired limits in Denver, Colorado. Thus, by determining the relative magnitude of the force of gravity at various locations in a predetermined geographic area, and assigning electronic correction factors in the microprocessor of the scale corresponding to those locations, it becomes possible to electronically recalibrate the scale by applying appropriate correction factors to the factory calibration of the scale depending on where the scale is ultimately.
Thus, the present invention is a method of recalibrating an electronic scale to indicate accurate weight measurements of articles placed on the scale regardless of variations in the force of gravity under which the scale is operating between a site of origin and a site of installation and which tend to adversely affect accurate weight. The method is typically practiced in conjunction with an electronic scale which has a load cell capable of producing an analog voltage output signal indicative of the weight of an article placed on the scale, an analog to digital converter for converting the analog voltage output signal from the load cell into digital information representing the analog output, a digital readout for displaying the weight of the article, and a microprocessor for converting the digital representation of the analog output of the load cell into information for driving the digital readout to cause it to display desired information.
In its broader aspects the method comprises the steps of generating first data relating to the effect on the accuracy of said scale due to variations in the relative magnitude of the gravitational force between a site of origin and a site of installation, at the site of origin placing the first data into the memory of a microprocessor in the scale, determining an electronic count 21708~3 differential between the scale with 0# weight on the platter and with a known weight thereon and placing the first electronic count differential into a memory to calibrate the scale for accurate weight measurement at the site of origin. The method further includes the steps of removing the scale from the site of origin to a site of installation at which the scale may operate under a gravitationa! force different from that which prevailed at the site of origin, and entering second data into the microprocessor relating to the relative magnitude of the gravitational force at the site of installation which causes the microprocessor to adjust the factory calibration to compensate for any variation in the gravitational force between the site of origin and the site installation, whereby the scale is recalibrated at the site of installation to cause the scale to indicate accurate weight measurements regardless of any variation in the gravitational force between the site of origin and the site of installation.
In some of its more limited aspects, the step of generating the first data includes the steps of assigning separate identifiers to the site of origin and the site of installation which are indicative of the relative magnitudes of the gravitational force at the site of origin and the site of installation respectively, and ascertaining an arithmetic multiplier for each of the magnitudes of gravitational force that will adjust the factory calibration of the scale to compensate for a difference in the gravitational force between that at the site of origin and that at the site of installation. Further, with the scale at a site of origin, the step of placing the first data into the memory of a microprocessor includes the step of placing the identifiers and the corresponding arithmetic multipliers into the memory of the microprocessor. Subsequently, with the scale at the site of installation, the step of entering the second data includesthe step of entering the identifier into the scale that corresponds to the site of installation of the scale, whereby the identifier causes the corresponding arithmetic multiplier to adjust the electronic count differential by the amount of the arithmetic multiplier to readjust the electronic count differential to compensate for the difference in the magnitude of gravitational force between the site of origin and the site of installation.
In a presently preferred mode of carrying out the invention, the geographic locations correspond to the locations identified by postal zone codes applicable to the predetermined geographic area in which the geographic locations are situated, which, at least in the case of the United States and Canada, can be conveniently represented by the first three digits of postal ZIP codes, although other forms of geographic location code systems could be effectively utilized, such as the telephone number area 21708~3 code system. Further, in one embodiment of the invention, the step of entering the identifier into the scale that corresponds to the geographic location of the site of installation comprises the step of manually entering theidentifier through a data entry component of the scale. In other embodiments, this step is carried out by inserting a PROM into the scale which contains either the identifier or the appropriate representation of a ZIP
or other geographic location code.
Having briefly described the general nature of the present invention, it is a principal object thereof to provide a method of recalibrating an electronicscale to indicate accurate weight measurements of articles placed on the scale regardless of variations in the relative magnitude of gravitational force under which the scale operates between a site of origin and a site of installation and which tend to adversely affect accurate weight.
Another object of the present invention is to provide a method of recalibrating an electronic scale according to the preceding object which does not require that an auxiliary weight be added to the platter of the scale in order to achieve a recalibration, thereby avoiding the expense of providing either a built in auxiliary weight that must be periodically added to the weight of the platter, or going through a complex series of steps as required with using a removable platter in lieu of an auxiliary weight.
These and other objects, advantages and features of the method of the present invention will become more apparent from an understanding of the following detailed description of a preferred embodiment of the invention when considered in conjunction with the accompanying drawings.
Description of the Drawings FIG. 1 is an exploded, perspective view of the major components of a representative electronic scale with which the method of the present invention is practiced.
FIG. 2 is a chart representing the relationship between all United States ZIP codes and corresponding identifiers which are indicative of the relative magnitude of gravitational force of the locations identified by the ZIPcodes.
FIG. 3 is a chart representing the relationship between the identifiers shown in Fig. 2 and arithmetic multipliers by which an electronic count differential in memory in the scale is adjusted to compensate for variations in the relative magnitude of gravitational force between the site of origin and the site of installation.
FIG. 4 is a relatively simple schematic of the principal control components of an electronic scale required for the practice of the present invention.
FIG. 5 is a view similar to Fig. 4 illustrating another embodiment of the practice of the present invention.
Detailed Description of the Invention Referring now to the drawings, and more particularly to Fig. 1 thereof, the major components of a representative scale with which the present invention is practiced are shown in an exploded manner, and are seen to comprise a housing, indicated generally by the reference numeral 10, a load cell, indicated generally by the reference numeral 12, a weight distribution plate, indicated generally by the reference numeral 14, a top cover, indicated generally by the reference numeral 16, and finally a platter, indicated generally by the reference numeral 18, on which the mail piece to be weighed is placed.
The housing 10 is generally rectangular and has oppositely disposed upstanding side walls 20, an upstanding rear wall 22, a very short, upstanding front wall 24, and a bottom wall 26 to which the side, rear and front walls are connected. A plurality of feet 28 are suitably connected to the underside of the bottom wall 26 in recesses defined by bosses 30 for supporting the scale. The housing 10, as well as the top cover 16 and the platter 18, are formed of injection molded polycarbonate blend plastic. An upstanding wall 32 extends across the housing 10 between the side walls 20 to divide the space within the base and housing 10 into forward and rearward compartments 34 and 36, the former for the electronic components which are actuated by a plurality of push buttons that extend through suitable openings 38 formed in the top cover 16, the latter for the load cell 12 and other electronic components that will not fit in the forward compartment 34.
A metal support plate 40 is suitably secured to the bottom wall 26 for supporting the fixed end 42 of the load cell 12, which is positioned on the support plate 40 and is connected to the housing 10 by suitable screws 44 which pass through openings in the bottom wall 26 and the support plate 40 and threadedly engage the fixed end 42 of the load cell 12. The opposite or free end 46 of the load cell 12 is connected to the weight distribution plate 14by means of similar screws 48 which pass through openings in the plate 14 and are threadedly engaged with the free end 46 of the load cell 12.
2I 7~ 853 The top cover 16 is dimensioned to overlie the housing 10, and includes a push button access portion 50 which includes the aforementioned button access openings 38 and overlies the forward compartment 34 in the housing 10. The remainder of the top cover 16 is a generally rectangular portion 52 which overlies the rearward compartment 36 in the housing 10. A
pair of screws 54 suitably connect the rectangular portion 52 of the top cover 16 to the upper ends 56 of a pair of posts 58 to secure the top plate 16 to the housing 10.
The scale platter 18 is basically a generally rectangular body member 60 which has approximately the same dimensions as the rectangular portion 52 of the top cover, and is provided with four identical legs 62, only two of which are shown in Fig.1. Each leg 62 extends through one of the openings 64 in the weight distribution plate 16 and seats firstly in the apertures 66 of one of a plurality of grommets 68 which in turn fit into suitable recesses 70 formed adjacent the four corners of the weight distribution plate 14. The legs 62 are gripped by the inner edges of the apertures 66 with sufficient strength to firmly retain the platter 18 on the weight distribution plate 14, but not so tightly that it cannot be readily removed by a user simply by lifting the platter upwardly. It should be noted that the openings 64 in the top cover 16 are sufficiently large to enable the legs 62 to pass freely therethrough without touching the inner edges of the apertures 66 so that the platter 18 is supported solely by the weight distribution plate 14, which, as described above, is in turn supported solely by the load cell 12.
It should be understood that the foregoing scale has been shown and described simply for the purpose of illustrating a type of electronic scale withwhich the present invention can be practiced, and that other scales having different forms of construction could be utilized.
Coming now to a detailed description of the method of the present invention, it will be seen that the invention, in its broader aspects, comprisesa series of steps directed toward generating certain data relating to the effecton the accuracy of the scale due to variations in the relative magnitude of the gravitational force between a site of origin and a site of installation, which data is later used when additional data is entered into the scale at a site of installation. It is possible that some of this data pre-exists, in which case itcan be utilized in the practice of the invention; if not, it must be ascertained.
In its more limited aspects, the invention also includes a series of steps that are carried out to generate the aforementioined data, and other steps are carried out in connection with how the additional data is entered into the scale. In order to facilitate a clear understanding of the invention, the 21 7l~853 g complete series of steps will be described in the sequence in which they are carried out in the most limited aspect of the invention, with the understanding that the breadth of the invention is not intended to be limited by this form of description, but rather only by reference to the claims appended hereto.
Assuming for the sake of this description that none of the necessary information already exists, and with reference to Fig. 2, the first step in the practice of the invention is to identify a predetermined number of geographic locations within a predetermined geographic area. This involves first making a determination of the geographic area, which may be the entire world or any portion thereof. For convenience of illustration, the predetermined geographic area is the United States, and the selected geographic locations are the areas within the United States identified by the first three digits of postal ZIP codes. As is well known, the U. S. Postal Service has established a zone system for the country in which postage rates between any two given zones are established for a given base weight. Also, all ZIP codes in the country are identified as being distributed among these zones. Thus, if one knows the ZIP code of the destination of a parcel, he can determine the postal zone for that destination, from which he can determine the rate per base weight, and by applying this to the weight of the parcel he determines the amount of postage required. It should also be understood that additional locations could be included, such as Europe, and additional geographic locations could be identified, again using postal zone codes for convenience, but other location codes, such as the aforementioned telephone area codes, could be utilized. The two letter state abbreviation system adopted by the U. S. Postal Service could also be utilized, and any of these systems could be utilized alone or in combination with other systems.
Thus, in the case illustrated in Fig. 2, it will be seen that all of the ZIP
codes in the United States have been listed in the first three digit format, buthave been grouped in a predetermined manner by closely adjacent ZIP
codes simply to reduce the number of geographic locations which must be identified. Column A shows a representative listing of ZIP codes in such groups, commencing with the lowest number existing ZIP code and ending with the highest number existing ZIP code.
The next step is to ascertain the relative magnitude of gravitational force for each of the geographic locations within the predetermined geographic area. This information generally exists and is available in some form for various parts of the world, but if a specific geographic location to becovered in the practice of the invention is one for which this information is not available, it must then be ascertained.
2~ 70853 Once the relative magnitude of gravitational force for all of the geographic locations has been ascertained, an arbitrary identifier is assigned to each of the geographic locations that is indicative of the relative magnitude of the gravitational force at each of these locations. As seen in Column B of Fig. 2, the identifiers, listed in Column B, are two digit numbers, although other forms of alpha or numeric designations could be used. Two digit numbers, assigned in random order, are preferred for security reasons so that owners of the scales cannot ascertain the identifiers for geographic locations other than the location at which the scale is installed. This prevents them from improperly recalibrating the scale to indicate a lower weight than the actual weight of a mail piece at the site of installation of thescale and consequently paying insufficient postage for that mail piece.
It will be seen from Fig. 2 that the same identifier is assigned to more than one geographic location for the reason that there are a large number of ZIP code areas in the United States where the gravitational force is the same. It should be understood, as previously mentioned, that the magnitude of gravitational force for any location is a function of the elevation of that location relative to sea level and the proximity of it to the equator. More particularly, the higher a point is above sea level, the lower is the gravitational force since it is further from the center of the earth. Similarly,the closer a point is to the equator, the less is the gravitational force due tocentrifugal force caused by the rotation of the earth which negatively affects gravitational force. Thus, a ZIP code in Boulder, Colorado, at an elevation of 5,000 feet, may have the same gravitational force as a ZIP code in San Diego, California at sea lev~' because the closer proximity of sea level Miami to the equator offsets the 5,000 foot elevation of Boulder, even though Denver i_ considerably farther from the equator than San Diego.
The next step is that of ascertaining an arithmetic multiplier for each of the different magnitudes of gravitational force that will adjust the factory calibration of the scale to compensate for a difference in the gravitational force between that at the site of origin of the scale, typically the factory, and that at the site of installation. Thus, with reference to Fig. 3, it will be seen that each of the gravitational identifiers listed in Column A has a corresponding arithmetic multiplier listed in Column B. How these multipliers work to recalibrate the scale at the site of installation will be fully explained below. However, it should be noted here that if a scale is installed at a location that has the same relative magnitude of gravitational force as that which exists at the site of origin of the scale, it is not necessary to recalibrate the scale since the factory calibration will suffice to cause the scale to provide accurate weight measurements at the site of installation.
Therefore, assuming that the identifier at the site of origin is #41, the corresponding multiplier for all ZIP codes having that gravitational force will be 1.000. Again for the sake of illustration, it has been assumed that the difference in the relative magnitude of gravitational force between the geographic locations identified by the gravitational identifiers 0.0005.
It should be noted at this point that the two previous steps, i.e., assigning an identifier to each geographic location and ascertaining an arithmetic multiplier, have been collectively designated, in a broader aspect of the invention, as generating first data relating to the effect on the accuracy of the scale due to variations in the relative magnitude of gravitational force between the site of origin and the site of installation, and in a slightly more limited aspect of the invention, as generating first data relating to the effecton the accuracy of the scale due to variations in the relative magnitude of gravitational force between all of the geographic locations.
The next step is to place the identifiers and the corresponding arithmetic multipliers, or the first data as the case may be, depending on whether one is considering the most limited aspect of the invention or one of the broader aspects as described above, into the memory of a microprocessor in the scale. Thus, with reference to the schematic diagram of Fig. 4, it will be seen that the scale includes a microprocessor 80 which includes several memory registers, one of which 82 is for permanent storage of the identifiers listed in Column A of Fig. 3. Another memory register 84 is for permanent storage of the multipliers listed in Column B of Fig. 3. This step is performed at the site of origin and is part of the general software installation for the scale.
The next step is to determine an electronic count differential between the scale with 0# weight on the platter and with a known weight on the platter, and placing the electronic count differential into a memory in the microprocessor to calibrate the scale for accurate weight measurement at the site of origin. The determination of the electronic count differential itself involves three successive steps, which commences with determining a raw electronic count of the scale with 0# weight on the platter which, by way of an example, might be 21,200. This is accomplished by the load cell 12 generating an analog voltage indicative of the weight of the empty platter 18.
Basically, a load cell, as seen in Fig. 1, using strain gage technology can be a generally rectangular metallic body member which is adapted to have one end 42 thereof rigidly mounted on a frame so that the load cell 12 is supported only at that end, with the rest of the body member being 21 708a3 cantilevered from the mounting end. The other end 46 of the body member is provided with some means for supporting a weight, such as the weight distribution plate 14 and the platter 18. Strain gages are mounted on the body member in appropriate locations that stretch very slightly when the body member is deflected by the application of the weight. An electric voltage is applied across the strain gage, the output of which varies in accordance with the extent to which the strip is strained by weight imposed on the free end of the body member. Referring to Fig. 4, the output load cell voltage is amplified by the amplifier 86 and applied to an analog to digital converter 88 which converts the analog voltage into a digital signal which can be recognized by a microprocessor 80 for further processing. In a manner known in microprocessor technology, the details of which are not necessary to an understanding of the invention, the microprocessor 80 converts the digital signal into a predetermined electronic count, which is transferred to and temporarily stored in a working memory register 90.
A known weight is then placed on the platter 18, which typically weighs approximately the same as the weight capacity of the scale, which in the scale disclosed herein is 5 pounds. A raw electronic count of the scale with the known weight on the platter 18 is then determined in the same manner as just described for determining and storing the raw electronic count of the scale with 0# weight on the platter 18, which, again by way of example, might be 1 10,100, and this count is also placed in the working memory register 90.
Again in known manner in microprocessor technology, the microprocessor accesses the two raw electronic counts in the working memory register 90 and subtracts the first count from the second count to determine a first electronic count differential, which in the example being given, is 88,900, and which represents the counts per known weight at the site of origin. This electronic count differential is then placed in a permanentmemory register 92.
The scale is then removed from the site of origin to the site of installation at one of the geographic locations at which the scale may operate under a gravitational force different from that which prevailed at the site of origin. At the site of installation, when the scale is first powered up, it prompts the operator to enter the identifier into the scale that corresponds to the geographic location of the site of installation, which he obtains from a chart supplied with the scale which, in the manner shown in abbreviated version in Fig. 2, lists the identifiers for all of the ZIP groups for the country.
This is accomplished most conveniently by utilizing the data entry keypad 94 of the scale which is also used to enter other information pertinent to determining the amount of postage required for the mail piece being weighed, such as the class of mail or a ZIP to Zone and special fees conversion factor in the case of a parcel, although some other form of data entry device could be utilized. The keypad 94 transmits this information to the identifier memory register 82 of the microprocessor, where, in a manner known in microprocessor technology, the corresponding identifier stored in the memory register 82 is accessed and transferred to the multiplier memory register 84. This in turn accesses the appropriate multiplier for the identifierjust accessed from the identifier memory register 82, and this multiplier is transferred to the storage memory 92 which contains the electronic count differential determined at the site of origin. The electronic count differential is then adjusted by the product of the multiplier and the electronic count differential to establish a new electronic count differential for the scale to compensate for the difference in the relative magnitude of gravitational force between the site of origin and the site of installation. In the example stated above, if it is assumed that the site of origin is Connecticut, and the site of installation is Boulder, Colorado, and that the identifier for Boulder is 76, then from Fig. 3, the new arithmetic multiplier is .9995, and the new electronic count differential for the scale in Boulder is 88,900 times .9995, or88.885.5. Thus, when an article is now placed on the scale, the accurate weight thereof will appear on the digital display 96.
Fig. 5 illustrates another embodiment of the invention in which the appropriate multiplier for the electronic count differential is selected by an identifier which in turn is selected by a ZIP code entered into the scale via a PROM. Although the above described ZIP code information is readily available on charts supplied with less sophisticated scales, most electronic scales are provided with software which includes the ZIP to ZONE
conversion information in the form of a ZIP to ZONE PROM, which is supplied with the scale. Thus, it will be apparent that if the ZIP code information shown in Fig. 2 is placed in memory in the microprocessor, as in the memory register 98 shown in Fig. 5, at the site of origin, and an appropriate PROM, as indicated by the box labeled 100 in Fig. 5, is inserted into the scale, either at the site of origin if the site of installation is then known, or at the site of installation itself, the site of installation ZIP code on the PROM will, again in a manner well known in microprocessor technology, access the appropriate ZIP code stored in the memory register 98 which, in turn, accesses the corresponding identifier from the memory register 82. The identifier then accesses the corresponding multiplier from the memory register 84, and the recalibration process described above can then take place.
One disadvantage of the embodiment just described is that it requires a substantially large capacity memory in the scale in order to store all of the ZIP code groups listed on the actual ZIP to identifier chart, and this tends to increase the cost of the scale. This disadvantage is overcome in another embodiment of the invention, which is a modification of that shown in Fig. 4, in which the appropriate identifier contained in the memory register 82 is accessed by entering the identifier for the site of installation through a PROM
which includes the identifier for the site of installation of the scale, rather than through the data entry keypad 94. This requires a further step in the overall process, that of placing the identifier in a PROM at the time that the ZIP code information for a particuiar scale is programmed into the PROM. Thus, if the PROM is already in the scale when it is first powered up at the site of installation, a recalibration will take place instantly.
In a still further embodiment of the invention, it is possible to enter the ZIP code of the site of installation through a data entry keypad in the same manner as the identifier was entered in the previously described embodiment illustrated in Fig. 4. The advantage of this is that the scale can be recalibrated at the site of installation in the event that the PROM is missing or defective when the scale is first powered up at the site of installation.
It is to be understood that the method of the present invention are not to be considered as limited to the practice of the specific steps described above, which are merely illustrative of the best mode presently contemplated for carrying out the method of the invention and which are susceptible to such changes as may be obvious to one skilled in the art, but rather they are intended to cover all such variations, modifications and equivalents thereof as may be deemed to be within the scope of the claims appended hereto.
Claims (16)
1. A method of recalibrating an electronic scale to indicate accurate weight measurements regardless of variations in the gravitational force under which the scale is operating between a site of origin and a site of installation which adversely effect the accuracy of the scale, said method comprising the steps of:
A. generating first data relating to the effect on the accuracy of said scale due to variations in the relative magnitude of gravitational force between a site of origin and a site of installation, B. at the site of origin, placing said first data into the memory of a microprocessor in the scale, C. determining an electronic count differential between the scale with 0# weight on the platter and with a known weight thereon and placing said electronic count differential into a memory to calibrate the scale for accurate weight measurement at the site of origin, D. removing the scale from the site of origin to a site of installation at which the scale may operate under a gravitational force different from that which prevailed at the site of origin, and E. entering second data into said microprocessor relating to the relative magnitude of the gravitational force at the site of installation which causes the microprocessor to adjust the factory calibration to compensate for any variation in the gravitational force between the site of origin and the site installation, whereby said scale is recalibrated at the site of installation to cause said scale to indicate accurate weight measurements regardless of any variation in the gravitational force between the site of origin and the site of installation.
A. generating first data relating to the effect on the accuracy of said scale due to variations in the relative magnitude of gravitational force between a site of origin and a site of installation, B. at the site of origin, placing said first data into the memory of a microprocessor in the scale, C. determining an electronic count differential between the scale with 0# weight on the platter and with a known weight thereon and placing said electronic count differential into a memory to calibrate the scale for accurate weight measurement at the site of origin, D. removing the scale from the site of origin to a site of installation at which the scale may operate under a gravitational force different from that which prevailed at the site of origin, and E. entering second data into said microprocessor relating to the relative magnitude of the gravitational force at the site of installation which causes the microprocessor to adjust the factory calibration to compensate for any variation in the gravitational force between the site of origin and the site installation, whereby said scale is recalibrated at the site of installation to cause said scale to indicate accurate weight measurements regardless of any variation in the gravitational force between the site of origin and the site of installation.
2. A method as set forth in Claim 1 wherein said step of generating said first data includes the steps of A. assigning an identifier to said site of origin and said site of installation which are indicative of the relative magnitudes of the gravitational force at said site of origin and said site of installation, and B. ascertaining an arithmetic multiplier for each of said magnitudes of gravitational force that will adjust said factory calibration of the scale to compensate for a difference in the gravitational force between that at the site of origin and that at the site of installation.
3. A method as set forth in Claim 2 wherein said step of entering said second data comprises the step of entering the identifier into the scale that corresponds to the site of installation of the scale, whereby said identifier causes the corresponding arithmetic multiplier to adjust said electronic count differential by the amount of said arithmetic multiplier to readjust said electronic count differential to compensate for said difference in the magnitude of gravitational force between said site of origin and said site of installation.
4. A method as set forth in Claim 3 wherein the step of entering the identifier into the scale that corresponds to the site of installation comprisesthe step of manually entering said identifier through a data entry component of the scale.
5. A method as set forth in Claim 3 wherein the step of entering the identifier into the scale that corresponds to the site of installation comprisesthe step of inserting a PROM into the scale which contains said identifier.
6. A method as set forth in Claim 2 wherein said step of entering said second data comprises the step of entering a geographic location code into the scale that corresponds to the site of installation of the scale, whereby said geographic location code selects the appropriate identifier for the site ofinstallation of the scale which identifier in turn causes the corresponding arithmetic multiplier to adjust said electronic count differential by the amountof said arithmetic multiplier to readjust said electronic count differential to compensate for said difference in the magnitude of gravitational force between said site of origin and said site of installation.
7. A method as set forth in Claim 6 wherein the step of entering said geographic location code into the scale that corresponds to the site of installation comprises the step of manually entering said geographic location code through a data entry component of the scale.
8. A method as set forth in Claim 6 wherein the step of entering the said geographic location code into the scale that corresponds to the site of installation comprises the step of inserting a PROM into the scale which contains said geographic location code.
9. A method of recalibrating an electronic scale to indicate accurate weight measurements regardless of variations in the gravitational force under which the scale is operating between a site of origin and a site of installation which adversely effect the accuracy of the scale, said method comprising the steps of:
A. identifying a predetermined number of geographic locations within a predetermined geographic area, B. ascertaining the relative magnitude of gravitational force at each of said geographic locations, C. generating first data relating to the effect on the accuracy of said scale due to variations in the relative magnitude of gravitational force at said locations, D. at a site of origin, placing said first data into the memory of a microprocessor in the scale, E. determining an electronic count differential between the scale with 0# weight on the platter and with a known weight thereon and placing said electronic count differential into a memory to calibrate the scale for accurate weight measurement at the site of origin, F. removing the scale from the site of origin to a site of installation at one of said geographic locations at which the scale may operate under a gravitational force different from that which prevailed at the site of origin, and G. entering second data into said microprocessor relating to the relative magnitude of the gravitational force at the site of installation which causes the microprocessor to adjust the factory calibration to compensate for any variation in the gravitational force between the site of origin and the site installation, whereby said scale is recalibrated at the site of installation to cause said scale to indicate accurate weight measurements regardless of any variation in the gravitational force between the site of origin and the site of installation.
A. identifying a predetermined number of geographic locations within a predetermined geographic area, B. ascertaining the relative magnitude of gravitational force at each of said geographic locations, C. generating first data relating to the effect on the accuracy of said scale due to variations in the relative magnitude of gravitational force at said locations, D. at a site of origin, placing said first data into the memory of a microprocessor in the scale, E. determining an electronic count differential between the scale with 0# weight on the platter and with a known weight thereon and placing said electronic count differential into a memory to calibrate the scale for accurate weight measurement at the site of origin, F. removing the scale from the site of origin to a site of installation at one of said geographic locations at which the scale may operate under a gravitational force different from that which prevailed at the site of origin, and G. entering second data into said microprocessor relating to the relative magnitude of the gravitational force at the site of installation which causes the microprocessor to adjust the factory calibration to compensate for any variation in the gravitational force between the site of origin and the site installation, whereby said scale is recalibrated at the site of installation to cause said scale to indicate accurate weight measurements regardless of any variation in the gravitational force between the site of origin and the site of installation.
10. A method as set forth in Claim 9 wherein said step of generating said first data includes the steps of A. assigning an identifier to each of said geographic locations that is indicative of the relative magnitude of the gravitational force for each of said geographic locations, and B. ascertaining an arithmetic multiplier for each of said magnitudes of gravitational force that will adjust the factory calibration of the scale to compensate for a difference in the gravitational force between that at the site of origin and that at the site of installation.
11. A method as set forth in Claim 10 wherein said step of entering said second data comprises the step of entering the identifier into the scale that corresponds to the geographic location at the site of installation of the scale,whereby said identifier causes the corresponding arithmetic multiplier to adjust said electronic count differential by the amount of said arithmetic multiplier to readjust said electronic count differential to compensate for saiddifference in the magnitude of gravitational force between said site of origin and said site of installation.
12. A method as set forth in Claim 11 wherein the step of entering the identifier into the scale that corresponds to the geographic location of the site of installation comprises the step of manually entering said identifier through a data entry component of the scale.
13. A method as set forth in Claim 11 wherein the step of entering the identifier into the scale that corresponds to the geographic location of the site of installation comprises the step of inserting a PROM into the scale which contains said identifier.
14. A method as set forth in Claim 10 wherein said step of entering said second data comprises the step of entering a geographic location code into the scale that corresponds to the geographic location at the site of installation of the scale, whereby said geographic location code selects the appropriate identifier for the site of installation of the scale which identifier in turn causes the corresponding arithmetic multiplier to adjust said electronic count differential by the amount of said arithmetic multiplier to readjust said electronic count differential to compensate for said difference in the magnitude of gravitational force between said site of origin and said site of installation.
15. A method as set forth in Claim 14 wherein the step of entering said geographic location code into the scale that corresponds to the geographic location of the site of installation comprises the step of manually entering said identifier through a data entry component of the scale.
16. A method as set forth in Claim 15 wherein the step of entering said geographic location code into the scale that corresponds to the geographic location of the site of installation comprises the step of inserting a PROM intothe scale which contains said identifier.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US39801295A | 1995-03-03 | 1995-03-03 | |
| US398,012 | 1995-03-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2170853A1 true CA2170853A1 (en) | 1996-09-04 |
Family
ID=23573628
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2170853 Abandoned CA2170853A1 (en) | 1995-03-03 | 1996-03-01 | Method of recalibrating electronic scales |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2170853A1 (en) |
| GB (1) | GB2298491B (en) |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH658722A5 (en) * | 1983-03-23 | 1986-11-28 | Mettler Instrumente Ag | SCALE WITH ACCELERATING WEIGHT INDICATOR AT THE LOCATION. |
| FR2580804B1 (en) * | 1985-04-22 | 1989-06-09 | Mors | METHOD AND DEVICE FOR CALIBRATING AND ADJUSTING WEIGHING SYSTEMS |
| AU2436588A (en) * | 1987-10-30 | 1989-05-04 | Pitney-Bowes Inc. | Apparatus for providing a geographically distinct gravitational constant in an electronic scale |
| DE4320892A1 (en) * | 1993-06-23 | 1995-01-05 | Mettler Toledo Albstadt Gmbh | Libra |
| GB9406863D0 (en) * | 1994-04-07 | 1994-06-01 | Ims Innovation Ltd | Weighing apparatus |
| GB9406875D0 (en) * | 1994-04-07 | 1994-06-01 | Ims Innovation Ltd | Weighing apparatus |
-
1996
- 1996-03-01 CA CA 2170853 patent/CA2170853A1/en not_active Abandoned
- 1996-03-04 GB GB9604626A patent/GB2298491B/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| GB2298491A (en) | 1996-09-04 |
| GB2298491B (en) | 1999-08-11 |
| GB9604626D0 (en) | 1996-05-01 |
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| Date | Code | Title | Description |
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| FZDE | Dead |