CN1035132C

CN1035132C - Small crystal-resonance digital-display electronic weigher

Info

Publication number: CN1035132C
Application number: CN95111139A
Authority: CN
Inventors: 武汉美
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-05-02
Filing date: 1995-07-27
Publication date: 1997-06-11
Anticipated expiration: 2015-07-27
Also published as: CN1115846A

Abstract

The present invention discloses a small crystal-resonance digital-display electronic weigher which is provided with a weigher body. A key board is arranged on the weighter body. Compared with the prior art, the small crystal-resonance digital-display electronic weigher has the differences that a force sensor of a piezoelectric quartz crystal plate is arranged in the weighter; the force sensor of a piezoelectric quartz crystal plate is connected with a main oscillator; a reference oscillator and the main oscillator are jointly connected with a frequency mixer; the output of the frequency mixer is connected with a low-pass filter; the low-pass filter is connected with a single chip microcontroller; the key board is also connected with the single chip microcontroller; the single chip microcontroller is also connected with a digital display; a power supply is connected with the circuits. The present invention has the advantages of small volume, low electric consumption, more functions, easy use and accurate weighing.

Description

Small crystal-resonance digital-display electronic weigher

The present invention relates to can produce the weighing apparatus that elastically-deformable element is a feature to use in the weighing technology, specifically, weighing parts wherein are to be in to be stressed or the solid form with piezoelectric properties of tension force effect when weighing.

Electronic scales is a kind of weighing apparatus of application electric technology, and existing commercial electronic scale is substantially by forming with the lower part: scale body, LOAD CELLS, signal processing circuit, power supply etc.LOAD CELLS wherein all adopts resistance strain type sensor basically, is equipped with the shearing girder structure; Signal processing circuit is basic circuit with the electric bridge, by the A/D transducer, converts digital signal to, proofreaies and correct, handles and show.The electronic scales of these existing employing resistance strain type sensors, because of the volume of sensor is big, the support circuit power consumption is many, and own wt is big, uses inconvenience, more is difficult to make portable product.

The purpose of this invention is to provide the small crystal-resonance digital-display electronic weigher that a kind of volume is little, in light weight, power consumption is low, easy to use.

Technical solution of the present invention is: a kind of small crystal-resonance digital-display electronic weigher, the scale body is arranged, on the scale body keyboard is arranged, the difference of itself and prior art is: a piezoelectric quartz crystal sheet force transducer is arranged in the scale body, piezoelectric quartz crystal sheet force transducer links to each other with king oscillator, reference oscillator and king oscillator connect frequency mixer jointly, frequency mixer output connects a low-pass filter, low-pass filter links to each other with a single chip microcontroller again, aforementioned keyboard also joins with single chip microcontroller, single chip microcontroller also is connected to digital indicator, and a power supply and above-mentioned each circuit join.

Digital indicator described in the present invention adopts the LCD LCD.Certainly, also can adopt other suitable digital indicators.But with liquid crystal be good because it has power saving, advantage such as durable.

Reference oscillator described in the present invention be connected to aforementioned piezoelectric quartz crystal sheet force transducer in the quartz crystal slice same type and the quartz crystal slice of temperature profile.Single chip microcontroller described in the present invention also is connected to detector unit.Described detector unit adopts the version of thermistor and another electric resistance partial pressure order sheet microcontroller.Certainly, also can adopt the element of other suitable temperature compensations carried out, detection and suitable version.

Single chip microcontroller described in the present invention also is connected to sensitivity switch is set.Certainly, also can adopt other the suitable version that can adjust the sensitivity of scale according to the discreteness of power sensing element.

Advantage of the present invention is: owing to adopted the piezoelectric quartz crystal sheet as the power sensing element and adopted the single chip microcontroller technology, the volume of electronic scales is reduced, power consumption reduces, the signal of output is delivered to the single chip microcontroller interface from crystal oscillator sensing oscillator to difference frequency, power consumption is about 6mW (3V, 2mA), and circuit such as existing strain resistor sensor, detection electric bridge, A/D, power consumption is generally 300mW (10V, 30mA), power consumption have only be originally 1/50.In addition owing to adopted the reference crystal and the power sensing crystal of same type, make zero point drift in 0.3 calibration, serviceability temperature detects the temperature coefficient of compensate for strain sensitivity, makes because the measurement that strain sensitivity causes is drifted about less than 0.5 calibration (10-40 ℃).The degree of accuracy of weighing is high.Owing to adopted single chip microcontroller, on the basis of weighing, also increased functions such as calculating and temperature survey demonstration, function increases enhancing.Because structural small and exquisite, can make portablely very easily, made things convenient for use.Certainly, the present invention also can make the desk-top scale of Denging.

Below in conjunction with drawings and Examples the present invention is described in further detail:

Fig. 1 is the theory diagram of the small-sized digital-display electronic weigher of a kind of resonant mode of the present invention.

Fig. 2 is the electrical schematic diagram of the single chip part in the adoptable circuit among the present invention.

Fig. 3 can adopt the electrical schematic diagram of the sensing circuit part in the circuit for the present invention.

Fig. 4 can adopt the structural representation of sensing mechanism for the present invention.

Accompanying drawing has been described principle of work of the present invention.A piezoelectric quartz crystal sheet force transducer CRY2 is arranged in the scale body, piezoelectric quartz crystal sheet wherein is as the load sensitive element, when the load carrier by power is passed to power above-mentioned piezoelectric quartz crystal sheet, the resonance frequency of crystal oscillator will change, and the changing value of frequency becomes proportional relation more accurately with the value of power.Piezoelectric quartz crystal sheet force transducer CRY2 links to each other with king oscillator 3, produce vibration output and be connected to frequency mixer 5, other has a reference crystal CRY1 to link to each other with reference oscillator 4, the vibration output of its generation is connected to another input end of frequency mixer 5, reference crystal CRY1 adopt with aforementioned piezoelectric quartz crystal sheet force transducer CRY2 in the piezoelectric quartz crystal sheet of same type and temperature characterisitic, cause that to overcome temperature frequency difference changes and causes the zero point drift of scale.The output of frequency mixer 5 is exported through low-pass filter 6 filtering, taking-up power sensing crystal oscillator frequency f0 with reference to the difference frequency (f0-f1) of crystal oscillator frequency f1, send single chip microcontroller U1 to carry out frequency measurement again, accurate corresponding relation according to the value of frequency change value and power draws the weighing value, and the LCD liquid crystal display displays through being attached thereto goes out instant weighing value.

Also use a thermistor RTC that temperature is detected among the present invention, because the resistance of thermistor RTC, change along with variation of temperature, the A/D input end that the partial pressure value of thermistor RTC and another resistance R 21 is delivered to single chip microcontroller U1 is made the Digital Detecting of temperature value, on the one hand can be directly in order to detected temperatures, and can come out by aforementioned LCD liquid crystal display displays, on the other hand, the force sensitivity coefficient of power sensing element is done temperature compensation according to detected temperature value.

In order to adjust the sensitivity of scale according to the discreteness of sensing element parameter easily aborning, adopted digital establishing method, added that a sensitivity is provided with switch 11, promptly the input port to single chip microcontroller U1 carries out the level setting, single chip microcontroller U1 is according to the scale-of-two code value of port input, determine its Sensitirity va1ue, guarantee the accuracy of scale, prevent that also the user from adjusting sensitivity privately simultaneously.

Also be added with keyboard 8 among the present invention,, play the function of counter to calculate input.Certainly, under suitable situation,, can not adopt this keyboard as another kind of embodiment.But must lack a common function, can be affected on the performance.

The present invention can adopt dry cell to make power supply because power consumption is little, certainly, add circuit such as voltage stabilizing, constitutes power circuit 13, supplies with so that single chip microcontroller etc. can obtain stablizing accurate electric energy.As another kind of embodiment, also can change or add the mains-supplied circuit.With serviceable life and the use easily and flexibly that prolongs dry cell as much as possible.

Fig. 2 has described the physical circuit of the single chip part in the adoptable circuit among the present invention.U1 wherein is the single chip microcontroller (as L1) with direct driving LCD ability, and it has the A/D translation function, and each parts of circuit are operated accordingly.The display driver port of single chip microcontroller U1 is connected with LCD display (LCD4*16), realizes 7 display drivers.Dynamic scan mode is adopted in the button input of keyboard, and PA0-PA2, PD2, PD3 are the scanning output line, and PA3-PA7 is the scanning incoming line.Resistance R 8, R9, R10, R11, R12, R13, R14, R15 link to each other with the port B of microcontroller, input port to single chip microcontroller carries out the level setting, single chip microcontroller determines its Sensitirity va1ue according to the value of port input, to guarantee the accuracy of scale.The resistance of thermistor RTC varies with temperature and changes, and the partial pressure value of thermistor RTC and resistance R 21 send the A/D input port of single chip microcontroller to make the Digital Detecting of temperature value.Also comprise elements such as piezoelectric quartz crystal sheet CRY1, capacitor C 1, C2, C4, C5, resistance R 1, R2, R3, R4, R5, R6, R16, R7, R17, R18, R19, R20 in the foregoing circuit.

Fig. 3 has described the physical circuit of the part of the sensing circuit in the adoptable circuit among the present invention.Wherein piezoelectric quartz crystal sheet CRY2 and capacitor C 33, C34, resistance R 32, R36 forms magnet oscillator circuit, the vibration output of its generation is connected to the input end of the frequency mixer of integrated circuit U32 (CD4011) composition, piezoelectric quartz crystal sheet CRY1 and capacitor C 31, C32, resistance R 31, R33 forms the reference oscillation circuit, its output is connected to another input end of frequency mixer, and the output of frequency mixer is through resistance R 33, R34, capacitor C 35, after the low-pass filter output that C36 forms, send aforementioned single chip microcontroller to carry out frequency measurement by the output of integrated circuit U31 (CD4069) phase inverter again.Also comprise capacitor C 37, C38, C39, resistance R 37, R38, R39, R40, R41, dry cell B1, elements such as diode D31, D32 in the foregoing circuit.

Power supply among the present invention adopts dry cell to make power supply, adds the mu balanced circuit that resistance R 38 and diode D31, two stabilivolts of D32 are formed, and supplies with so that single chip microcontroller etc. can obtain stable electric energy.

Fig. 4 has described the present invention can adopt sensing mechanism.Its support beam 41, support beam 41 that has an insulating material to make is divided into two parts (certainly, also can be left and right sides two parts under the suitable situation) up and down by a slit 42, but two parts at one end are still continuous up and down; At the disjunct other end piezoelectric quartz crystal sheet chamber 43 is arranged, piezoelectric quartz crystal sheet CRY2 is housed in the chamber 43, have connecting line to link to each other on the piezoelectric quartz crystal sheet CRY2 with its related elements; One end of a load bar 44 is fixed on the top part of support beam 41, and passes two parts up and down of the support beam that comprises aforementioned slit 42, and load bar 44 lower ends are connected to steelyard hook 46 by force transmission element 45.When reality was used, under weight effect on the steelyard hook 46, load bar 44 was the tension of two parts up and down of support beam 41, made the stressed generation transducing signal of piezoelectric quartz crystal sheet CRY2, and drew weighing data by single chip microcontroller etc.

If when the present invention made forms such as platform balance, power transmission and load-carrying construction that steelyard hook etc. can be suitable substituted, to adapt to the overall structure form of corresponding scale.

Claims

1, a kind of small crystal-resonance digital-display electronic weigher, the scale body is arranged, on the scale body keyboard is arranged, it is characterized in that: a piezoelectric quartz crystal sheet force transducer is arranged in the scale body, the support beam that sensor has an insulating material to make, support beam is divided into two parts up and down by a slit, but two parts at one end still link to each other up and down, at the other end piezoelectric quartz crystal sheet chamber is arranged, the piezoelectric quartz crystal sheet is housed in the chamber, the piezoelectric quartz crystal sheet has connecting line, one end of a load bar is fixed on the top part of support beam, and pass two parts up and down of the support beam that comprises aforementioned slit, load bar lower end is connected to steelyard hook, piezoelectric quartz crystal sheet force transducer links to each other with king oscillator, be connected in reference oscillator with aforementioned piezoelectric quartz crystal sheet force transducer in the quartz crystal slice same type and the quartz crystal slice of temperature profile, reference oscillator and king oscillator connect frequency mixer jointly, frequency mixer output connects a low-pass filter, low-pass filter links to each other with a single chip microcontroller again, aforementioned keyboard also links to each other with single chip microcontroller, single chip microcontroller also is connected to the LCD liquid crystal digital display and sensitivity is provided with switch, and a power supply and above-mentioned each circuit join.

2, small crystal-resonance digital-display electronic weigher according to claim 1, it is characterized in that: described frequency mixer is made up of the Sheffer stroke gate of integrated circuit CD4011 or other model, the output of king oscillator and reference oscillator is connected to two input ends of Sheffer stroke gate respectively, the output of Sheffer stroke gate realizes that through the low pass filter output that R33, R34, C35, C36 form difference frequency detects.

3, small crystal-resonance digital-display electronic weigher according to claim 1 and 2 is characterized in that: described sensitivity is provided with switch, adopts digital establishing method, and the input port of single chip microcontroller is carried out the level setting, input scale-of-two code value.