CN110865325B - Calibration device and calibration method of instantaneous interruption tester - Google Patents
Calibration device and calibration method of instantaneous interruption tester Download PDFInfo
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Abstract
The invention discloses a calibration device and a calibration method for a transient interruption tester, belonging to the technical field of calibration of transient interruption testers and comprising two parts of transient interruption judgment resistance parameter calibration and transient interruption time measurement parameter calibration; the RH series or RL series resistors are connected into or out of the circuit through the program control relay, so that the continuous adjustment of the resistance values of the high-resistance source and the low-resistance source in an output range can be realized; the method for calibrating the transient interruption time measurement parameters adopts a method of combining a standard signal generating circuit and a high-speed field effect tube to generate a transient interruption time standard value, and can simulate the transient interruption state by controlling the on-off state and the on-off duration of the high-speed field effect tube, thereby realizing the calibration of the transient interruption time measurement parameters of the transient interruption tester. The scheme of combining a standard signal generating circuit with a program-controlled resistance source is adopted, the program-controlled resistance source realizes the calibration of the transient interruption judgment resistance, and the standard signal generator and the high-speed field effect tube are combined to realize the calibration of transient interruption time measurement.
Description
Technical Field
The invention belongs to the technical field of calibration of a transient interruption tester, and particularly relates to a calibration device and a calibration method of the transient interruption tester.
Background
The instantaneous interruption tester is one of transient resistance testing devices, and is widely applied to the fields of aerospace, aviation and the like. The device is mainly used for vibration test occasions of electric connectors and relays, and can give an alarm and display instantaneous interruption time when the contact resistance of the electric connectors and the relays is larger than a certain set judgment resistance value. The working principle of which is shown in figure 1,
principle of instantaneous interruption tester: the measured resistor, a voltage source inside the instantaneous interruption tester and a voltage dividing resistor form a measuring loop. The voltage values at two ends of the tested resistor are compared with the comparison voltage in the instrument, and if the input voltage is greater than the comparison voltage, an instantaneous interruption pulse width is formed. Counting is performed using a constant frequency time signal source beginning at the rising edge of the glitch pulse and off at the falling edge of the glitch pulse. The count value generated from the rising edge to the falling edge is multiplied by the period of the time base signal, i.e. the glitch time.
The traditional calibration method of the instantaneous interruption tester has the following defects:
parameters to be calibrated of the instantaneous interruption tester mainly comprise an instantaneous interruption judgment resistance parameter and an instantaneous interruption time measurement parameter, and the calibration method of the two parameters in the traditional method comprises the following steps:
instantaneous interruption determination of resistance parameters: the resistance value change is realized by manually rotating the material object resistance box, the alarm is instantly given out until the transient resistance testing equipment starts to alarm, the resistance value of the standard resistance box at the moment is recorded, and if the resistance value falls into the allowable error of the resistance value setting, the qualification is judged.
Instantaneous interruption time measurement parameters: the standard signal generator is connected to two ends of the loop, the frequency and duty ratio of the standard signal generator are set, the signal generator sends out 0.1-99.99 mu s pulse square wave, the display value of the instantaneous interruption tester is compared with the input pulse square wave signal, and when the display value is the same as or not more than the allowable test error of 0.1 mu s, the instrument can work normally.
The traditional calibration method has the following defects:
1) when the standard resistance box is manually adjusted, false alarms of a transient interruption tester can be generated due to instantaneous open circuit.
2) The instantaneous interruption tester is a multi-channel measuring device. The traditional calibration method has the common defects of manual calibration such as large workload, low speed and the like.
3) The method for step-by-step calibration of the transient resistance parameter and the transient interruption time parameter is inconsistent with the actual application scene of the transient interruption tester.
Disclosure of Invention
The invention aims to solve the technical problem of the traditional calibration mode of the transient interruption tester, and provides a calibration device and a calibration method of the transient interruption tester, which are convenient for metrologists to carry out daily calibration on the transient interruption tester.
The invention adopts the following technical scheme for solving the technical problems:
a calibration device for a transient interruption tester comprises two parts, namely transient interruption judgment resistance parameter calibration and transient interruption time measurement parameter calibration;
wherein, the parameter calibration of the instantaneous interruption judgment resistance is realized by a program control resistance source;
the program-controlled resistance source comprises a high-resistance source sequence (RH) formed by connecting n resistance sequences in series, a high-value part for forming a high-resistance source value, and a low-resistance source sequence (RL) formed by connecting n resistance sequences in parallel through a relay, wherein the low-value part for forming the high-resistance source or the low-resistance source is independently used as a low-resistance source to be output;
the RH or RL series resistors are connected into or out of the circuit through the program control relay, so that the continuous adjustment of the resistance values of the high-resistance source and the low-resistance source in an output range can be realized;
the method for calibrating the transient interruption time measurement parameters adopts a method of combining a standard signal generating circuit and a high-speed field effect tube to generate a transient interruption time standard value, and can simulate the transient interruption state by controlling the on-off state and the on-off duration of the high-speed field effect tube, thereby realizing the calibration of the transient interruption time measurement parameters of the transient interruption tester.
The utility model provides a calibration method based on transient interruption tester calibrating device, when the transient interruption of calibrating transient interruption tester judges resistance parameter and transient interruption time measurement parameter simultaneously, the response speed of resistance can influence the calibration result of transient interruption time measurement parameter, and programme-controlled resistance source can't realize 30 ns's response speed, consequently adopt the change process of three cycle to realize resistance change process, then the calibration of transient interruption time measurement parameter will not receive programme-controlled resistance source response time's influence, the calibration of transient state judgement resistance will not receive field effect transistor on-resistance's influence yet, specifically contain following step:
step one, controlling the period of an output pulse signal to be T and the duty ratio to be 90% by an FPGA;
step two, setting the resistance value of the main program control resistor source as R1 in the on-time of the high-speed field effect tube; when the field effect tube is disconnected, the resistance value of the connected calibrated instrument is R1, and the time is 0.1T; observing whether the instantaneous interruption tester gives out light or gives a buzzing alarm or not;
step three, if the alarm is not given in the step two, the high-speed field effect tube is connected, and the resistance value of the main program control resistor source is set to be R0 within the connection time of the high-speed field effect tube; when the field effect tube is disconnected, the resistance value of the connected calibrated instrument is R0, and the time is 0.1T; observing whether the instantaneous interruption tester gives out light or gives a buzzing alarm or not;
step four, if the alarm is not given in the step three, the high-speed field effect tube is switched on, and the resistance value of the main program control resistor source is set to be R2 within the switching-on time of the high-speed field effect tube; when the field effect tube is disconnected, the resistance value of the connected calibrated instrument is R2, and the time is 0.1T; observing whether the instantaneous interruption tester gives out light or gives a buzzer alarm or not and whether the displayed instantaneous interruption time is 0.1T or not; and if the calibrated instantaneous interruption tester gives an alarm and the displayed instantaneous interruption time is within the specified error range, the instantaneous interruption tester is calibrated to be qualified.
As a further preferred scheme of the calibration device of the instantaneous interruption tester, the standard signal generating circuit sends out 0.1-99.99 mu s full-range vibration-free pulse square waves, and the high-speed field effect tube is an N-channel junction type field effect tube NPTB 00004A.
As a further preferable scheme of the calibration device for the transient interruption tester of the invention, a method of combining a standard signal generating circuit and a high-speed field effect transistor is adopted to generate a transient interruption time standard value, which is specifically as follows: adjusting a standard signal generator to generate square wave signal output, enabling the output voltage to be larger than the conduction voltage of the field effect transistor, enabling the field effect transistor to be in a connection state, adjusting the frequency corresponding to the time needing to be calibrated, and setting the duty ratio to be 50%; pressing a start test key to start testing, and recording a standard instantaneous interruption time value and a time indication value of the instantaneous interruption tester at the moment after the instantaneous interruption tester gives an alarm; the output voltage and the pulse width of the signal generating circuit are controlled to realize the calibration of the transient interruption time, and the high-speed field effect tube is screened by adopting the high-bandwidth digital storage oscilloscope, so that the response time of the high-speed field effect tube is less than 30ns, and the calibration requirement that the transient interruption time error is not more than 30ns can be met.
As a further preferred scheme of the calibration device for the transient interruption tester of the invention, a successive approximation algorithm is adopted to realize continuous adjustment of the resistor, a successive approximation method is adopted to approximate the set resistance value, 4 real resistors are adopted in each 10-time process, and the residual value is gradually transmitted to the next stage from high to low until the set value is reached, so that the set resolution is met, and the method specifically comprises the following steps:
step 2, comparing the residual high-value resistance set value obtained in the step 1 with the next high-value resistance in the same step 1, and further determining the relay state of the next high-value resistance;
step 3, comparing the resistance values in the remaining high-resistance source resistance sequence in sequence according to the step 1, determining the corresponding relay state, and transmitting the residual value to the set value of the high-resistance source;
step 4, solving the admittance of the residual resistance value in the step 3, and comparing the admittance of the low-resistance source sequence from high to low, thereby determining the relay state of the low-resistance source sequence;
and 5, if only the low-resistance source output is needed, starting from the step 4 to determine the relay state of the low-resistance source sequence resistor.
As a further preferred scheme of the transient interruption tester calibration device, the principle of a successive approximation method is used to know that each gear can meet the same effect as a resistance box with 10 groups of resistors in each gear only by 4 groups of single-value resistors, and the residual value is transferred to the next gear each time to realize the final resolution; the resistor setting is achieved using series connected physical resistors.
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
1. aiming at the problems existing in the traditional calibration mode of the transient interruption tester, a novel calibration method of the transient interruption tester is provided, and a calibration device is developed, so that the daily calibration of a metering staff on the transient interruption tester is facilitated. The calibration method provided by the invention adopts a scheme of combining a standard signal generating circuit with a program-controlled resistance source, the program-controlled resistance source realizes the calibration of 'instantaneous interruption judgment resistance', and a standard signal generator and a high-speed field effect tube are combined to realize the calibration of 'instantaneous interruption time measurement'. Compared with the traditional calibration method, the calibration method of the transient interruption tester is optimized, the calibration efficiency is improved, and the problems of large workload, low speed and the like of the traditional manual calibration are solved;
2. the calibration method provided by the invention can realize the development of the calibration device of the transient interruption tester, is used for the calibration work of the transient interruption tester in the aerospace and industry, ensures the reliability of contact devices such as a connector, a relay and the like, and provides a metering guarantee for model development. The result can be used in the acceptance test, the test and calibration after maintenance, the test and calibration before major model tasks, the weekly inspection and other work newly purchased by the existing and future aerospace and industrial transient interruption tester in China, has important significance for the quality control of product development, and can improve the calibration efficiency and reduce the manpower.
Drawings
FIG. 1 is a schematic diagram of the internal principle of a snap-off tester;
FIG. 2 is a schematic diagram of a transient interruption tester calibration method;
FIG. 3 is a block diagram of a high and low impedance source;
FIG. 4 is a calibration connection graph of the hit time of the hit tester;
FIG. 5 is a diagram illustrating the ideal variation of the external resistor during calibration;
fig. 6 is a transient resistance change curve.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the attached drawings:
the invention provides a scheme of combining a program-controlled resistance source, a standard signal generating circuit and a high-speed field effect transistor, which comprises 16 paths. The parameter calibration of 'instantaneous interruption judgment resistance' is realized by a program control resistance source, the parameter calibration of 'instantaneous interruption time measurement' is realized by a signal generating circuit and a high-speed field effect tube, and the specific schematic diagrams are shown in figures 1 and 2.
Program-controlled resistance source scheme for parameter calibration of instantaneous interruption judgment resistance
The invention fully utilizes the calibration value of each resistor, combines an algorithm, calculates the combination of the relay switch, realizes the accurate setting of 10m omega-10G omega, and has the error less than 0.1 percent. Can cover the resistance range of 1 omega-5 k omega.
The low-resistance source range is continuously adjustable from 100m omega to 10k omega, and the high-resistance source range is continuously adjustable from 10k omega to 10G omega. The low-resistance sources are connected in parallel, and the high-resistance sources are connected in series.
The low-range part of the low-resistance source and the low-resistance source are cascaded, and the specific implementation block diagram is shown in fig. 3.
As shown in fig. 3, the series of resistances of RH1, RH2 … RHn are connected in series and function to constitute the high value part of the high source resistance. The resistance value of a single RH series is relatively large (larger than 10k omega), the withstand voltage of a high-value resistor is also relatively high, and the used relay is a high-voltage relay with the withstand voltage level of more than 3000V.
The resistance value of the low-resistance source ranges from 100m omega to 10k omega, and the maximum load current is 400 mA. The resistor sequences of RL1 and RL2 … RLn are connected in parallel with each other through relays (the resistance ranges of the resistor sequences are wide and range from 100M omega to 10M omega), and the resistor sequences are used for forming a low-value part of a high-resistance source or are independently output as a low-resistance source. The low resistance source is either a 2-port output or a 4-port output.
By program control of on-off of the relays, RH or RL series resistors are connected into or out of the circuit, continuous adjustment of resistance values of the high-resistance source and the low-resistance source in an output range can be realized, the resolution of the high-resistance source can reach 4 bits and half or more, and the low-resistance source can reach 3 bits and half or more.
In the selection of the resistor, the error grade of the resistor is higher than the nominal index of the final output resistor, and if the error grade of the final output resistor is 0.2%, the error grade of the resistor is selected to be 0.05% so as to ensure the final index requirement. As shown in fig. 3, a block diagram of a high and low resistance source.
Successive approximation algorithm for realizing continuous adjustability of resistance
The method for realizing the continuous output of the resistor under the condition of a certain resolution ratio is to adopt a successive approximation method to approximate the set resistance value, 4 real resistors are adopted in each 10 times of the process, and the residual value is gradually transmitted to the next stage from high to low until the set value is reached, so that the set resolution ratio is met.
The software algorithm of the switch of the program control relay is
Firstly, comparing a set value of high resistance with the highest value in an RH sequence, and if the set value is greater than the compared resistance value, subtracting the compared value from the set value, and connecting a resistor of the compared value into a circuit (setting the corresponding relay state as off); if the set value is smaller than the compared resistance value, the set value is unchanged, and the resistor with the compared value is not connected into the circuit (the corresponding relay state is set to be closed);
secondly, comparing the obtained rest set values with the secondary high-value resistor, calculating according to the step 1, and determining the relay state of the secondary high-value resistor
Comparing the resistance values with the residual RH series according to the steps, determining the corresponding relay state, and transmitting the residual value to the set value of the low resistance source
And step four, obtaining the admittance of the residual resistance value in the step (3), and comparing the admittance of the RL sequence from high to low to determine the relay state of the RL sequence.
Fifthly, if only the low-resistance source output is needed, starting from the step (4), determining the relay state of the RL sequence resistance.
Because in actual engineering, the resistance value is often not an integer, and the composition mode can be various, for example, the resistance value of 4 resistors in each 10 times of the range is adopted, and 8, 4, 2, 1 or 5, 3, 2, 1 or 0.91, 1.5, 3.3, 5.1 and the like can be realized.
Self-calibration technical scheme of resistance source
After the resistor box or the programmable resistor source is calibrated, the contact resistance of the switch and the resistance of the resistor can shift along with time, so that the synthesized resistance value exceeds a nominal error range.
This offset in resistance can be achieved by recalibration of the resistance. The re-calibrated resistance value of the resistance box needs to be obtained by looking up documents during the use process, and the use is inconvenient. The program-controlled resistance source of the research adopts a special recalibration program, uses a high-precision table, is matched with the switching of a relay, measures the single resistance values at the output end of the equipment, stores the single resistance values into an internal memory of the equipment, and then uses the latest calibration value to calculate when the resistance is synthesized, so that the output resistance is ensured to be more accurate.
Method for selecting resistance values of series-parallel resistors
10 sets of resistors are required to be selected in each 10-system gear of the common resistor box, and each set of resistors realizes 10 integral values from 0 to 9. Because the resistors have certain errors and the nominal value of the resistors is usually not an integer, each set of resistors needs to be trimmed by a plurality of resistors to achieve the nominal integer value output.
As can be seen from the above principle of successive approximation, each gear only needs 4 groups of single-value resistors to satisfy the same effect as the resistor box with 10 groups of resistors in each gear. Because it is based on the principle that each time the remaining value is passed to the next gear, the final resolution is achieved.
Method for selecting and proving gear resistance of each decimal measuring range
Research shows that in order to realize continuous adjustment of the resistance, 4 groups of resistance values are required for each 10-system gear, and the 4 groups of resistance values can not be integers and can be flexibly and variously formed. This provides great flexibility in the choice of resistors, and the following analysis considers a sufficient requirement for choosing the 4 sets of resistances without considering resistance errors.
One theoretically sufficient requirement for achieving a resistance setting using series-connected real resistors, abbreviated as condition 1, is given below and demonstrated.
1. Each 10-system range of the resistor setting range adopts 4 resistors, and the value of the combination of the resistors is k1R1+k2R2+k3R3+k4R4In which K isiIs 0 or 1. Wherein R is1≤R2≤R3≤R4They only represent the value of this decimal place, the true resistance value needs to be multiplied by a weighted power corresponding to the decimal place. These 4 resistances can be grouped into 16 discrete values, which can be expressed as a0, a1, a2, A3, a4, a5, A6, a7, A8, a9, a10, a11, a12, a13, a14, a15 by nominal value calculation. Wherein A isi≤Ai+1It is clear that a0 ═ 0 and a15 ═ R1+R2+R3+R4(ii) a This condition is simply referred to as condition 1 a.
2、Ai+1-Ai1 or less, and A15Not less than 9; this condition is simply referred to as condition 1 b.
The adequacy of this condition was first demonstrated below
For convenience of description, it is assumed that one resistance value can be reduced or enlarged 10mA double, expressed as the following formula,
R0＝N0+N1*10-1+N2*10-2+N3*10-3+N4*10-4+N5*10-5+……Nn*10-n，
in the above formula, NiTaking an integer of 0 to 9, N is known from the above conditions0、N1、N2、N3、N4、N5、……NnEach gear corresponds to 4 resistors.
Step 1: first, to determine N0Four resistors of (2) are connected to each otherElectrical state), obviously 0. ltoreq.R0< 10, the following state A certainly exists according to the above condition 1b0i≤R0＜A0i(+1Or A0,15≤R0< 10 because A0(i+1)-A0i1 or less and A15Not less than 9, so R is not less than 00-A0iR < 1 or 0. ltoreq.0-A0,15< 1, it can be seen that step 1 determines N0The four resistors of (2) are in corresponding connection state (relay state K)0i) And the remaining value is controlled to be within 1 and then passed to the remaining calculations.
Step 2: the residue value is more than or equal to R and is less than or equal to 0 after the above operation0-A0i< 1, it can be seen from the condition 1b that there is definitely one A1jR is more than or equal to 00-A0i-A1j*10-1< 0.1, from which it can be seen that step 2 determines N1The four resistors of (2) are in corresponding connection state (relay state K)1j) And the remaining value is controlled to be within 0.1 and then passed to the remaining calculations.
And step 3: one can also find such an A2kR is more than or equal to 00-A0i-A1j*10-1-A2k*10-2< 0.01, from which it can be seen that step 3 determines N2The four resistors of (2) are in corresponding connection state (relay state K)2k) And the error is controlled to be within 0.01 and then passed on to the rest of the calculation. According to the iteration principle, R is more than or equal to 00-A0i-A1j*10-1-A2k*10-2-…-Anm*10-n＜10-n。
The above reasoning shows that the successive approximation method can use the physical resistance satisfying the conditions 1a and 1b to carry out infinite approximation on the output resistance, thereby achieving the engineering application with a certain accuracy level. Condition 1 set forth above is therefore a sufficient condition.
It is demonstrated that the following condition 1 is also a requirement
Looking at the condition 1b, if the discrete value formed by combining several physical resistors does not satisfy the following condition
Ai+1-AiLess than or equal to 1, an i will appear to satisfy Ai+1-Ai1, in order to not lose generality, assume that A appears at the first stage0(i+1)-A0i> 1, then one R can be found0Make A a0i＜R0＜A0(i+1)And R is0-A0iMore than 1, therefore, after the first stage realizes the successive approximation algorithm, the value left to the later stage is more than 1, and theoretically, the later stage can not ensure that the R can be converged certainly0
Otherwise if A is not satisfied15If not less than 9, A will appear15< 9, in order not to lose generality, assume that A occurs at the first stage0,15< 9, then one R can be found0Make A a0,15＜R0< 10, and R0-A0,15More than 1, therefore, after the first stage realizes the successive approximation algorithm, the value left to the later stage is more than 1, and theoretically, the later stage can not ensure that the R can be converged certainly0。
It follows that either of the two conditions of condition 1b must be satisfied to be able to approximate the set value R with discrete resistance values according to the resolution of the last stage0。
Referring to the condition 1a again, if the discrete resistance value selected for each decimal range in the condition 1a is less than 4, and if it is 3, it is obvious that a of the condition 1b cannot be satisfiedi+1-Ai≦ 1, since 3 discrete values can have up to 7 values other than 0, 9 cannot be divided into 8 intervals all less than 1.
It follows that condition 1 set forth above is also a necessary condition when selecting a discrete dot resistance value.
The same principle can give a theoretical sufficient necessary condition for realizing the resistance source setting value by using the parallel physical resistance.
1. The resistance setting is first converted into admittance, 4 resistances are used per 10 times the journey, their value is k1G1+k2G2+k3G3+k4G4In which K isiIs 0 or 1. Wherein G is1≤G2≤G3≤G4They only represent the value of this decimal place, the true resistance value needs to be multiplied by a weighted power corresponding to the decimal place. The 4 admittances may be combined into 16 discrete values, which may be represented as B by a nominal value calculation0，B1，B2，B3，B4，B5，B6，B7，B8，B9，B10，B11，B12，B13，B14，B15. Wherein B isi≤Bi+1Is apparent from B0＝0，B15＝G1+G2+G3+G4This condition is abbreviated as Condition 2a
2、Bi+1-B i1 or less, and B15Not less than 9, this condition is abbreviated as Condition 2 b.
Method and proof for selecting resistor in each decimal range considering resistor error range
The resistance values mentioned above are nominal values of the resistors and the errors in the values after their combination are weighted errors of these resistor errors, it is clear that the errors are linearly related to the accuracy level of these resistors. The level of accuracy of the resistance can be increased in order to achieve higher final accuracy of the resistance source.
There is also a method to make the result more accurate, that is, after the resistor is assembled, the single resistance values are measured by using a higher precision meter and switching of the relay, and the measured value is used to replace the original nominal value to calculate, so as to obtain a more accurate output value of the resistor source.
When the discrete point resistance value is selected, when the error of the nominal value is considered, the above-mentioned conditions may be not satisfied, so that the error cannot be converged when the discrete resistor is used for realizing the final output resistor, and the error becomes larger. One method and condition for how to select the combination of resistances when using a nominal resistance of a certain error level is given below.
1. Taking 4 resistors per 10-system range of resistor setting range after combinationA value of k1R1+k2R2+k3R3+k4R4In which K isiIs 0 or 1. Wherein R is1≤R2≤R3≤R4The maximum error range of the resistance is +/-alpha%, the maximum error range of the resistance only represents the numerical value of the decimal position, and the real resistance value needs to be multiplied by the weighted power of the corresponding decimal position. The 4 resistors can be grouped into 16 discrete values, which can be expressed as A by nominal value calculation0，A1，A2，A3，A4，A5，A6，A7，A8，A9，A10，A11，A12，A13，A14，A15. Wherein A isi≤Ai+1It is clear that a0 ═ 0 and a15 ═ R1+R2+R3+R4(ii) a This condition is simply referred to as condition 3 a.
2、Ai+1-Ai1-alpha% 15, and
this condition is simply referred to as condition 3 b.
First we see k1R1+k2R2+k3R3+k4R4The distribution and variation of the values, as shown in table 1,
TABLE 1
The main intention of listing the above table is to examine the error between two adjacent discrete values due to the real resistance value relative to the nominal value, and find the maximum error term, which still satisfies the condition of condition 1 above.
If the resistance is corrected according to the resistanceQuasi-value (approximate true value) calculation, then AiA shift from the nominal value will occur, the maximum shift occurring at ai+1Upward bias, AiWhen the deviation is downward and the condition 1b is still satisfied, the
Ai+1+Ai+1*α％-Ai+Ai*α％≤ 1
A15-A15*α％≥9
The maximum shift is calculated below, and observing the above table reveals that the maximum shift occurs at K4K3K2K10111 and K4K3K2K11000, wherein Ai+1+Ai＝A15，A15≤15
It follows that if Ai+1-AiLess than or equal to 1-alpha% and 15 is true, Ai+1+Ai+1*α％-Ai+Ai*α％≤ 1
From A15-A15Alpha% is not less than 9, can be obtained
Similarly, the method and conditions for selecting the nominal value resistor with error grade are used to realize the set resistor source output under the condition that the resistors are connected in parallel, and the admittance errors are the maximum error of the resistors within +/-alpha% in each 10-system gear
(Positive error) and
(negative error)
1. The resistance setting is first converted into admittance, 4 resistances are used per 10 times the journey, their value is k1G1+k2G2+k3G3+k4G4In which K isiIs 0 or 1. Wherein G is1≤G2≤G3≤G4They only represent this decimal fileThe value of a bit, the true resistance value, needs to be multiplied by a weighted power corresponding to the decimal place. The 4 admittances may be combined into 16 discrete values, which may be represented as B by a nominal value calculation0，B1，B2，B3，B4，B5，B6，B7，B8，B9，B10，B11，B12，B13，B14，B15. Wherein B isi≤Bi+1Is apparent from B0＝0，B15＝G1+G2+G3+G4This condition is abbreviated as condition 4a
2、
And is
This condition is simply referred to as condition 4 b.
From the above inference
From this it can be concluded that if
If it is true, the above formula is true
By
Can obtain
Instantaneous interruption time parameter calibration-standard signal generating circuit and high-speed field effect transistor are combined
The invention adopts a method of combining a standard signal generating circuit and a high-speed field effect tube to generate a transient interruption time standard value, and realizes the calibration of transient interruption time measurement parameters of a transient interruption tester. As shown in fig. 4, a calibration connection graph of the snap off time of the snap off tester.
The standard signal generating circuit sends out 0.1-99.99 mus full-range vibration-free pulse square wave, the display value of the instrument is compared with the input pulse square wave signal, and the instrument can work normally when the display value is the same as or not more than the allowable test error.
The invention selects an N-channel junction field effect transistor NPTB00004A, which has the following main characteristics: when Vgs < -2V, the tube is in a turn-off state; when Vgs < -0.7V, the tube is in a conducting state and can bear the maximum current of 1.4A. The maximum test voltage of the instantaneous interruption tester is 12V, the test current is 1A/100mA/10mA, and the internal voltage-dividing resistors are 12 omega, 120 omega and 1200 omega respectively. When the field effect tube is in a connection state, the resistance at two ends of the DS is very small, and the voltage drop at two ends of the DS is about 0V; when the field effect transistor is in an off state, the resistance at the two ends of the DS is close to infinity, and the voltage drop at the two ends of the DS is about 12V. Therefore, the instantaneous interruption state can be simulated by controlling the on-off state and the on-off duration of the field effect transistor.
And adjusting the standard signal generator to generate square wave signal output, so that the output voltage is greater than the conduction voltage of the field effect transistor, and the field effect transistor is in a connection state. Adjusting the frequency corresponding to the time needing to be calibrated (for example, at the time point of calibrating 5 mus, the duty ratio is 50%, the period of the signal generator should be set to 10 mus, the corresponding frequency should be 0.1MHz, and the rest time points are obtained by analogy), and setting the duty ratio to be 50%; pressing a start test key to start testing, and recording a standard instantaneous interruption time value (50% of the period value of the standard signal generator) and a time indication value of the instantaneous interruption tester at the moment after the instantaneous interruption tester gives an alarm.
The output voltage and the pulse width of the signal generating circuit are controlled to realize the calibration of the transient interruption time, and the high-speed field effect tube is screened by adopting the high-bandwidth digital storage oscilloscope, so that the response time of the high-speed field effect tube is less than 30ns, and the calibration requirement that the transient interruption time error is not more than 30ns can be met.
A calibration step:
when calibrating the parameter of 'instantaneous interruption determination resistance', the resistance value R is calibrated0When the external resistor needs to be gradually increased from a value slightly smaller than the calibrated value to a value slightly larger than the calibrated value, and whether the calibrated instantaneous interruption resistance instrument gives an alarm or not is observed. Namely, the external resistance changing step is shown in fig. 5, note: in the figure R1Slightly smaller than R0，R2Is slightly larger than R0。
When the "instantaneous interruption determination resistance" parameter and the "instantaneous interruption time measurement" parameter of the instantaneous interruption tester are calibrated at the same time, the response speed of the resistance in fig. 2 influences the calibration result of the "instantaneous interruption time measurement" parameter. And the programmable resistance source can not realize the response speed of 30ns, so that the ideal resistance change process in fig. 5 is realized by adopting the change process of three periods in fig. 6, the calibration of the 'transient off time measurement' parameter is not influenced by the response time of the programmable resistance source, and the calibration of the 'transient judgment resistance' is not influenced by the on-resistance of the field effect transistor. R in FIG. 61Slightly smaller than R0，R2Is slightly larger than R0。
The method comprises the following steps: the FPGA controls the period of the output pulse signal to be T and the duty ratio to be 90%.
Step two: setting the resistance value of the main program control resistor source to R in the on-time of the field effect tube1(ii) a When the field effect tube is disconnected, the resistance value of the connected calibrated instrument is R1Time is 0.1T; and observing whether the instantaneous interruption tester gives out light or gives a buzzer alarm.
Step three: if no alarm is given in the second step, the field effect tube is switched on, and the resistance value of the main program control resistor source is set to be R within the switching-on time of the field effect tube0(ii) a When the field effect tube is disconnected, the resistance value of the connected calibrated instrument is R0Time is 0.1T; and observing whether the instantaneous interruption tester gives out light or gives a buzzing alarm.
Step four: if no alarm is given in the third step, the FET is turned on, and the resistance value of the main program control resistor is set to R within the time of turning on the FET2(ii) a When the field effect tube is disconnected, the resistance value of the connected calibrated instrument is R2Time is 0.1T; tester for observing instantaneous interruptionWhether to give out light or buzz alarm, and whether the displayed instantaneous interruption time is 0.1T. And if the calibrated instantaneous interruption tester gives an alarm and the displayed instantaneous interruption time is within the specified error range, the instantaneous interruption tester is calibrated to be qualified.
Through the four steps, the change process of the resistor in the figure 6 can be realized, and the parameters of the instantaneous interruption time and the instantaneous interruption judgment resistor can be synchronously calibrated without mutual influence.
And (3) analysis: resistance R of external transient resistor1，R0，R2The voltage is generated by a main program control resistance source, so that the on-resistance of the field effect transistor influences the resistance value output precision.
The time of transient resistance transient increase, i.e., "instantaneous off-time measurement" t1, is determined by the off-time of the fet, and is dependent only on the response speed of the fet, and is independent of the response speed of the programmable resistance source.
As described above, some of the meters perform calibration of the "determination of the instantaneous interruption resistance" parameter and the "measurement of the instantaneous interruption time" parameter of the instantaneous interruption tester in the following manner.
Instantaneous interruption determination of resistance parameters: the resistance value change is realized by manually rotating the material object resistance box, the alarm is instantly given out until the transient resistance testing equipment starts to alarm, the resistance value of the standard resistance box at the moment is recorded, and if the resistance value falls into the allowable error of the resistance value setting, the qualification is judged.
Instantaneous interruption time measurement parameters: the standard signal generator is connected to two ends of the loop, the frequency and duty ratio of the standard signal generator are set, the signal generator sends out 0.1-99.99 mu s pulse square wave, the display value of the instantaneous interruption tester is compared with the input pulse square wave signal, and when the display value is the same as or not more than the allowable test error of 0.1 mu s, the instrument can work normally.
The instantaneous interruption tester is a multi-channel measuring device. The traditional calibration method has the common defects of manual calibration such as large workload, low speed, fine operation, fussy operation, dryness, easy fatigue and the like.
The method for step-by-step calibration of the transient resistance parameter and the transient interruption time parameter is inconsistent with the actual application scene of the transient interruption tester.
The invention provides a novel method for calibrating a transient interruption tester, which can realize synchronous calibration of a transient interruption time parameter and a transient interruption judgment resistance parameter and is more appropriate to the real use scene of the transient interruption tester.
The calibration method provided by the invention can avoid instantaneous disconnection misoperation caused by manually rotating the resistance box in the traditional calibration mode, and the calibration result is more reliable.
The calibration method provided by the invention can realize calibration of instantaneous interruption testers with different specifications by controlling the output value of the program control resistance source and the period of the signal generating circuit, and has strong universality.
The calibration method provided by the invention can realize 16-path synchronous calibration of the transient interruption tester, and improves the calibration efficiency.
In the program-controlled resistor source scheme, the invention provides a theoretical sufficient requirement of series connection and parallel connection of 4 resistors with 10-system measuring ranges, and provides a basis for resistor type selection.
In the program control resistance source scheme, the invention provides a method for improving the output accuracy of a resistance source, which is to perform online calibration on each physical resistance and calculate according to the calibrated value.
The invention provides a sufficient condition for selecting the resistor under the condition that the resistor has an error range, and provides a basis for resistor type selection.
The scheme of 'generating instantaneous interruption time' provided by the invention has small error generated by the instantaneous interruption time, which is less than 30 ns.
Claims (6)
1. A transient interruption tester calibrating device is characterized in that: the device comprises a program control resistance source, a program control relay, a signal generating circuit and a high-speed field effect transistor; the program-controlled resistance source is used for calibrating instantaneous interruption judgment resistance parameters;
the program-controlled resistance source comprises a resistance source sequence RH formed by connecting more than two resistance sequences in series and a low-resistance source sequence RL formed by connecting more than two resistance sequences in parallel through a relay; the RH is used for forming a high-value part of a high-resistance source value, and the RL is used for forming a low-value part of the high-resistance source or is independently used as a low-resistance source to be output;
the program control relay is used for connecting the RH series resistor or the RL series resistor into or out of the circuit and continuously adjusting the resistance values of the high-resistance source and the low-resistance source in an output range;
when the program control resistance source is used for calibrating instantaneous interruption judgment resistance parameters, an instantaneous interruption time standard value is generated by adopting a method of combining a standard signal generating circuit and a high-speed field effect tube, and the instantaneous interruption state can be simulated by controlling the on-off state and the on-off duration of the high-speed field effect tube, so that the calibration of the instantaneous interruption time measurement parameters of the instantaneous interruption tester is realized.
2. A method for calibrating a transient interruption tester is characterized by comprising the following steps: when the transient interruption determination resistance parameter and the transient interruption time measurement parameter of the transient interruption tester are calibrated simultaneously, the response speed of the resistor can influence the calibration result of the transient interruption time measurement parameter, and the program-controlled resistance source can not realize the response speed of 30ns, so the change process of the resistor is realized by adopting the change process of three periods, then the calibration of the transient interruption time measurement parameter will not be influenced by the response time of the program-controlled resistance source, and the calibration of the transient determination resistance will not be influenced by the on-resistance of the field effect tube, the method comprises the following steps:
step one, a field programmable gate array FPGA controls an output pulse signal period to be T, and the duty ratio is 90%;
step two, setting the resistance value of the main program control resistor source as R1 in the on-time of the high-speed field effect tube; when the field effect tube is disconnected, the resistance of the calibrated instrument is R1, and the time is 0.1T; observing whether the instantaneous interruption tester gives out light or gives a buzzing alarm or not;
step three, if the alarm is not given in the step two, the high-speed field effect tube is connected, and the resistance value of the main program control resistor source is set to be R0 within the connection time of the high-speed field effect tube; when the field effect tube is disconnected, the resistance value of the connected calibrated instrument is R0, and the time is 0.1T; observing whether the instantaneous interruption tester gives out light or gives a buzzing alarm or not;
step four, if the alarm is not given in the step three, the high-speed field effect tube is switched on, and the resistance value of the main program control resistor source is set to be R2 within the switching-on time of the high-speed field effect tube; when the field effect tube is disconnected, the resistance value of the connected calibrated instrument is R2, and the time is 0.1T; observing whether the instantaneous interruption tester gives out light or gives a buzzer alarm or not and whether the displayed instantaneous interruption time is 0.1T or not; and if the calibrated instantaneous interruption tester gives an alarm and the displayed instantaneous interruption time is within the specified error range, the instantaneous interruption tester is calibrated to be qualified.
3. The method of calibrating a snap tester as claimed in claim 2, wherein: the standard signal generating circuit sends out 0.1-99.99 mu s full-range vibration-free pulse square waves, and the high-speed field effect tube is an N-channel junction field effect tube NPTB 00004A.
4. A method for calibrating a snap tester as claimed in claim 3, wherein: the method for generating the instantaneous interruption time standard value by combining the standard signal generating circuit and the high-speed field effect transistor comprises the following specific steps: adjusting a standard signal generator to generate square wave signal output, enabling the output voltage to be larger than the conduction voltage of the field effect transistor, enabling the field effect transistor to be in a connection state, adjusting the frequency corresponding to the time needing to be calibrated, and setting the duty ratio to be 50%; pressing a start test key to start testing, and recording a standard instantaneous interruption time value and a time indication value of the instantaneous interruption tester at the moment after the instantaneous interruption tester gives an alarm; the output voltage and the pulse width of the signal generating circuit are controlled to realize the calibration of the transient interruption time, and the high-speed field effect tube is screened by adopting the high-bandwidth digital storage oscilloscope, so that the response time of the high-speed field effect tube is less than 30ns, and the calibration requirement that the transient interruption time error is not more than 30ns can be met.
5. The method of calibrating a snap tester as claimed in claim 2, wherein: the method adopts a successive approximation algorithm to realize the continuous adjustment of the resistor, adopts a successive approximation method to approximate the set resistance value, adopts 4 real resistors in each 10 times of process, gradually transfers the residual value to the next stage from high to low until the set value is reached, and meets the set resolution ratio, and comprises the following specific steps:
step 1, comparing the acquired high-value resistance set value with the highest value in the high-resistance source resistance sequence, if the high-value resistance set value is larger than the compared resistance value, subtracting the compared value from the high-value resistance set value, and switching in the resistance of the compared value into a circuit, and setting the corresponding relay state as off; if the set value of the high-value resistor is smaller than the compared resistance value, the set value of the high-value resistor is unchanged, the resistor with the compared value is not connected into the circuit, namely the corresponding relay state is set to be closed;
step 2, comparing the residual high-value resistance set value obtained in the step 1 with the next high-value resistance in the same step 1, and further determining the relay state of the next high-value resistance;
step 3, comparing the resistance values in the remaining high-resistance source resistance sequence in sequence according to the step 1, determining the corresponding relay state, and transmitting the residual value to the set value of the high-resistance source;
step 4, solving the admittance of the residual resistance value in the step 3, and comparing the admittance of the low-resistance source sequence from high to low, thereby determining the relay state of the low-resistance source sequence;
and 5, if only the low-resistance source output is needed, starting from the step 4 to determine the relay state of the low-resistance source sequence resistor.
6. The method of calibrating a snap tester as recited in claim 5, wherein: according to the principle of a successive approximation method, 4 groups of single-value resistors are needed for each gear to meet the same effect as a resistor box with 10 groups of resistors for each gear, and the residual value is transmitted to the next gear every time to achieve the final resolution; the resistor setting is achieved using series connected physical resistors.
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