A programmable resistance and a method for calibrating a resistance strain gauge based on the programmable resistance

Abstract

The application discloses a programmable resistance and a resistance strain gauge calibration method based on the programmable resistance, and belongs to the technical field of sensors. The resistance strain gauge calibration method based on the programmable resistance comprises the following steps: providing a to-be-measured strain bridge; connecting the strain bridge to a constant current source, and connecting the negative pole of the constant current source to the ground; wherein, each bridge arm of the strain bridge is provided with a resistance strain gauge, and the resistance strain gauge on one bridge arm is further connected in series with a programmable resistance; applying the same pressure value to each resistance strain gauge, measuring the output voltage of the strain bridge at least three different temperature values; adjusting the programmable resistance so that the difference between the output voltages measured at any two times is zero, and recording the resistance value of the programmable resistance; and taking the average of the recorded resistance values of the programmable resistance as the resistance value connected to the strain bridge. Through the compensation of the resistance value of the programmable resistance, the measurement error caused by the resistance value change of the resistance strain gauge due to the temperature change is corrected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a programmable resistance and a resistance strain gauge calibration method based on the programmable resistance. BACKGROUND

[0002] The resistance strain gauge is a kind of element for measuring the small strain of the strain gauge, and the size of the pressure causing the strain of the strain gauge is calculated by measuring the change of the resistance value. Usually, a special resistance measurement circuit is designed to convert the relative change of the resistance into voltage and current, so as to facilitate the detection by the ready-made instruments and meters. The most common measurement circuit is the direct current bridge and the alternating current bridge. The bridge is a commonly used circuit composed of four resistance strain gauges. By applying a certain direct current or alternating current voltage to two input ports, the resistance value on the bridge has a nearly linear relationship with the output voltage of the two output ports. Through this linear relationship, the numerical change corresponding to the change of the resistance value is obtained.

[0003] The direct current bridge outputs direct current, and has high precision. The connection wire has low requirement and will not cause distribution parameters. When realizing the pre-adjustment balance, the circuit is simple, and only the pure resistance needs to be adjusted. Moreover, the high-stability direct current power supply is easy to obtain, which also reduces the requirement for the bridge equipment. However, it has the shortcomings of introducing power frequency interference, easily producing zero drift, and the subsequent circuit needs to use a direct current amplifier.

[0004] The alternating current bridge is a bridge for measuring by using sinusoidal voltage. It can eliminate the influence of power supply drift on the measurement result, and improve the measurement precision. However, considering the limitation of the signal frequency and amplitude, it is not suitable for all measurement occasions, and it has high non-linear error.

[0005] In order to reduce the non-linear error of the semiconductor strain bridge, a constant current source is usually used as the power supply of the semiconductor strain bridge. However, after the resistance is produced, each resistance will have a certain error compared with the nominal value. Moreover, the resistance is not only a function of pressure, but also a function of temperature, and the resistance value will also change at different temperatures. Therefore, when the bridge measurement is performed, there is also a problem of how to correct the error caused by the temperature and the resistance value calibration error.

[0006] It should be noted that the information disclosed in the background section of the present application is only intended to deepen the understanding of the general background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes the prior art known to those skilled in the art. SUMMARY

[0007] The purpose of the present application is to provide a programmable resistance and a resistance strain gauge calibration method based on the programmable resistance, so as to solve the problem of the temperature-induced error of the resistance strain gauge in the strain bridge.

[0008] To solve the above technical problems, the application provides a programmable resistance, comprising:

[0009] a control chip, having a VREF interface and a VOUT interface, for outputting a corresponding voltage value from the VOUT interface based on a reference voltage input to the VREF interface, to control the resistance of the programmable resistance;

[0010] an NMOS, having a seventh resistance, a fifth resistance and a sixth resistance connected to the source, the drain and the gate of the NMOS respectively, one end of the fifth resistance being connected to ground, wherein the drain of the NMOS is used to input a signal, one end of the seventh resistance being used to output a signal, and one end of the seventh resistance being also connected to ground;

[0011] a voltage amplification module, having an input end connected to the source of the NMOS, and an output end connected to the VREF interface;

[0012] an isolation module, having an input end connected to one end of the fifth resistance close to the NMOS, and an output end connected to a voltage division module;

[0013] a second operational amplifier, having a non-inverting input end connected to an output end of the voltage division module, an inverting input end connected to the VOUT interface, and an output end connected to one end of the sixth resistance away from the NMOS, and having a second capacitor connected in series between the inverting input end and the output end.

[0014] Preferably, the voltage amplification module comprises a third operational amplifier, the source of the NMOS is connected to a non-inverting input end of the third operational amplifier, an inverting input end of the third operational amplifier is connected to ground through a ninth resistance, an eighth resistance is connected in series between the inverting input end and the output end of the third operational amplifier, and the output end of the third operational amplifier is connected to the VREF interface.

[0015] Preferably, the non-inverting input end of the third operational amplifier is also connected to a second power supply, and the inverting input end of the third operational amplifier is also connected to ground through a third capacitor.

[0016] Preferably, the isolation module comprises a first operational amplifier, the non-inverting input of the first operational amplifier is connected to one end of the fifth resistor close to the NMOS tube, the inverting input and the output of the first operational amplifier are connected, the non-inverting input of the first operational amplifier is also connected to a third power supply, and the inverting input of the first operational amplifier is also grounded through a first capacitor.

[0017] Preferably, the voltage division module comprises a tenth resistor, an eleventh resistor and a twelfth resistor connected in series, the tenth resistor is connected to the output of the first operational amplifier, the first end of the twelfth resistor is connected to the eleventh resistor, the second end of the twelfth resistor is grounded, and the first end of the twelfth resistor is connected to the non-inverting input of the second operational amplifier.

[0018] The application also provides a resistance strain gauge calibration method based on a programmable resistance, which adopts the programmable resistance and further comprises the following steps.

[0019] A to-be-measured strain bridge is provided, the strain bridge is connected to a constant current source, and the negative electrode of the constant current source is grounded, wherein each bridge arm of the strain bridge is provided with a resistance strain gauge, and the resistance strain gauge on one bridge arm is further connected in series with the programmable resistance;

[0020] The same pressure value is applied to each resistance strain gauge, and the output voltage of the strain bridge is measured at at least three different temperature values;

[0021] The programmable resistance is adjusted to make the difference between the output voltages measured at any two times be zero, and the resistance value of the programmable resistance is recorded;

[0022] The average of the recorded resistance values of the programmable resistance is taken as the resistance value connected to the strain bridge.

[0023] Preferably, five different temperature values are uniformly taken in the working temperature range of the resistance strain gauge, and the output voltage of the strain bridge is measured at the five different temperature values.

[0024] Preferably, the programmable resistance is adjusted to make the difference between the output voltages at two adjacent temperature values be zero, and the resistance value of the programmable resistance is recorded.

[0025] Preferably, the step of adjusting the programmable resistance to make the difference between the output voltages measured at any two times be zero comprises changing the resistance value of the programmable resistance by inputting a required value to a control chip.

[0026] Preferably, the step of adjusting the programmable resistance to make the difference between the two measured output voltages zero comprises changing the resistance value of the programmable resistance by adjusting the resistance value of the seventh resistor.

[0027] In the programmable resistance provided by the present application, the resistance value of the programmable resistance is inputted by the control chip, so that the method is simple and arbitrary resistance value adjustment can be realized.

[0028] In the resistance strain gauge calibration method based on the programmable resistance provided by the present application, the measurement error of the resistance strain gauge caused by the resistance value change due to temperature change is corrected by the compensation of the resistance value of the programmable resistance. Specifically, the resistance value of the programmable resistance in one bridge arm of the bridge is adjusted to control the output voltage of the strain bridge at different temperatures to be the same, and the average of the resistance values of the programmable resistance measured for multiple times is taken as the resistance value of the resistance connected in the strain bridge, so that the error caused by temperature is reduced and the measurement precision of the measurement circuit is improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Fig. 1 is a schematic diagram of the resistance strain gauge calibration method of one embodiment of the present application;

[0030] Figure 2 Fig. 2 is a schematic diagram of the hardware circuit of the programmable resistance of one embodiment of the present application;

[0031] Figure 3 Fig. 3 is a flow chart of the resistance strain gauge calibration method of one embodiment of the present application.

[0032] In the figures:

[0033] 100, control chip; 200, isolation module; 300, voltage division module; 400, voltage amplification module. DETAILED DESCRIPTION

[0034] The programmable resistance and the method for calibrating the resistance strain gauge based on the programmable resistance are further described in detail below in combination with the drawings and specific embodiments. The advantages and features of the present application will be more apparent from the following description. It should be noted that the drawings are very simplified and all use non-precise proportions, only for the purpose of facilitating and clarifying the description of the embodiments of the present application. It should be understood that the drawings of the description do not necessarily show the specific structure of the present application in proportion, and the illustrative features for illustrating some principles of the present application in the drawings of the description will also be slightly simplified. The specific design features of the present application disclosed herein, such as specific sizes, directions, positions and shapes, will be determined partly by the specific application and use environment. In the following description of the embodiments, the same reference signs are sometimes used in different drawings to represent the same parts or parts with the same function, and the repeated description is omitted. In this description, similar signs and letters are used to represent similar items, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0035] In addition, the terms "first", "second" are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0036] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the skilled in the art can combine and combine the different embodiments or examples described in the description and the features of the different embodiments or examples without contradiction.

[0037] The inventor found that the existing temperature compensation method in resistance strain gauge measurement needs complex circuit compensation, resulting in increased cost of the measurement circuit; and the full-bridge circuit compensation method through the Wheatstone bridge assumes that the change values of each resistance with temperature are completely the same, but in actual situation, even the resistances with the same resistance value will produce different resistance value changes with temperature due to the characteristics of components, thereby resulting in poor compensation effect of the method.

[0038] Therefore, the application provides a resistance strain gauge calibration method based on programmable resistance, please refer to Figures 1-3 , which is a schematic diagram of an embodiment of the application, comprising the following steps:

[0039] S1: providing a to-be-tested strain bridge, the strain bridge is connected to a constant current source, and the negative electrode of the constant current source is grounded, wherein a resistance strain gauge is arranged on each bridge arm of the strain bridge, and the resistance strain gauge on one bridge arm is further connected in series with a programmable resistance.

[0040] S2: applying the same pressure value to each resistance strain gauge, and measuring the output voltage of the strain bridge at at least three different temperature values.

[0041] S3: adjusting the programmable resistance so that the difference between any two measured output voltages is zero, and recording the resistance value of the programmable resistance.

[0042] S4: taking the average of the recorded resistance values of the programmable resistance as the resistance value connected to the strain bridge.

[0043] The existing resistance strain gauge calibration method usually has two kinds, one needs a large number of complicated compensation circuits to compensate for temperature drift, and the other is to assume that the resistance connected to the bridge has the same temperature change characteristic. However, in actual production, even if the resistances with the same resistance value cannot guarantee that their temperature change characteristics are the same, the actual situation is ignored, that is, even if the resistances with the same resistance value, the resistance value change caused by temperature change is different, which leads to the measurement error of the resistance strain gauge. The application adjusts the programmable resistance on one bridge arm of the strain bridge by connecting a programmable resistance, so that the measurement results of the resistance strain gauge under different temperatures for the same pressure are the same, and the average of the recorded resistance values of the programmable resistance is taken, which reduces the measurement error of the resistance strain gauge caused by temperature change and improves the measurement accuracy of the measurement circuit.

[0044] As Figure 1 shown, the calibration is carried out under a force standard machine, a temperature controller controls the temperature, the strain bridge includes a first resistance strain gauge R1, a second resistance strain gauge R2, a third resistance strain gauge R3 and a fourth resistance strain gauge R4, wherein the first resistance strain gauge R1 and the second resistance strain gauge R2 are connected in series to form a first half bridge, the third resistance strain gauge R3 and the fourth resistance strain gauge R4 are connected in series to form a second half bridge, and the two half bridges are connected in parallel, Figure 1 the A and B ends are connected to a constant current source I for power supply, the C and D ends are connected out for measuring the output voltage, and the B end is also grounded, and the second resistance strain gauge R2 is connected in series with a programmable resistance ΔR.

[0045] In a certain pressure and temperature range, the resistance changes with pressure and temperature approximately linearly. Assuming that the first resistance strain gauge R1 changes with temperature at a rate of k1 and changes with pressure at a rate of λ1, the resistance value at the rated pressure and temperature is denoted as r1; the resistance value of the second resistance strain gauge R2 at the rated pressure and temperature is denoted as r2; the change rate of the third resistance strain gauge R3 with temperature is denoted as k3, and the change rate with pressure is denoted as λ3, the resistance value at the rated pressure and temperature is denoted as r3; the resistance value of the fourth resistance strain gauge R4 at the rated pressure and temperature is r4; the resistance value of the programmable resistance ΔR is Δr. The temperature at the time of measurement is T A and T B . The current output by the constant current source I is i, the current I1 flowing into the first half-bridge is i1, and the current I2 flowing into the second half-bridge is i2. Then:

[0046]

[0047] Solving the equations simultaneously, we get:

[0048]

[0049]

[0050] The output voltage is:

[0051]

[0052] When the temperature is T A , the output voltage is:

[0053]

[0054] When the temperature is T B , the output voltage is:

[0055]

[0056] Then the difference between the measurement values at different temperatures and the same pressure value is:

[0057]

[0058] Based on the above analysis, it can be known that by adjusting the resistance value Δr of the programmable resistance ΔR, ΔU0 can be made to be 0, so as to eliminate the measurement error caused by temperature, that is, in the case where the pressure does not change, the temperature changes, but the measurement result of the bridge formed by the resistance strain gauges does not change, so as to realize the measurement calibration of the resistance strain gauges.

[0059] In one embodiment, the working temperature range of each of the resistance strain gauges is the same, five different temperature values are evenly taken in the working temperature range of the resistance strain gauges, and the output voltage of the strain bridge is measured at the five different temperature values. The programmable resistance is adjusted to make the difference of the output voltage at two adjacent temperature values be zero, and the resistance value of the programmable resistance is recorded. Alternatively, five different temperature values are evenly taken in the environmental temperature range in which the strain bridge needs to work.

[0060] In one embodiment, the above-mentioned programmable resistance-based resistance strain gauge calibration method adopts the programmable resistance as shown in FIG. 1, and the programmable resistance comprises: Figure 2

[0061] a control chip 100 having a VREF interface and a VOUT interface, for outputting a corresponding voltage value from the VOUT interface based on a reference voltage input to the VREF interface, to control the resistance value of the programmable resistance;

[0062] an NMOS tube Q1, a source, a drain and a gate of the NMOS tube Q1 being connected with a seventh resistance R7, a fifth resistance R5 and a sixth resistance R6 respectively, one end of the fifth resistance R5 away from the NMOS tube Q1 being grounded, wherein the drain of the NMOS tube Q1 is used to access a signal input end, one end of the seventh resistance R7 away from the NMOS tube Q1 is used to output a signal output end, and one end of the seventh resistance R7 away from the NMOS tube Q1 is also grounded;

[0063] a voltage amplification module 400, an input end of the voltage amplification module 400 being connected with the source of the NMOS tube Q1, and an output end of the voltage amplification module 400 being connected with the VREF interface of the control chip 100;

[0064] an isolation module 200, an input end of the isolation module 200 being connected with one end of the fifth resistance R5 close to the NMOS tube Q1, and an output end of the isolation module 200 being further connected with a voltage division module 300;

[0065] ​The second operational amplifier U2 has its non-inverting input connected to the output terminal of the voltage dividing module 300, and its inverting input connected to the VOUT interface of the control chip 100. The output terminal of the second operational amplifier U2 is connected to one end of the sixth resistor R6 away from the NMOS transistor Q1. The second capacitor C2 is connected in series between the inverting input and the output terminal of the second operational amplifier U2. The second operational amplifier U2 functions as a comparator to compare the output voltage of the VOUT interface with the output voltage of the voltage dividing module 300. If the two voltages are the same or the output voltage of the voltage dividing module 300 is higher than the output voltage of the VOUT interface, the NMOS transistor Q1 is turned on.

[0066] The isolation module 200 includes the first operational amplifier U1. The non-inverting input of the first operational amplifier U1 is connected to one end of the fifth resistor R5 close to the NMOS transistor Q1. The inverting input and the output terminal of the first operational amplifier U1 are connected. The non-inverting input of the first operational amplifier U1 is also connected to the third power supply VCC3. The inverting input of the first operational amplifier U1 is also connected to the first capacitor C1.

[0067] The fifth resistor R5 has a resistance of 2kΩ, the sixth resistor R6 has a resistance of 100Ω, the seventh resistor R7 has a resistance of 0.5Ω, the NMOS transistor Q1 has a model number of YJ3404A, the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3 all have a model number of RS8552XM, the first capacitor C1 has a capacitance of 104F, the second capacitor C2 has a capacitance of 1nF, the third capacitor C3 has a capacitance of 104F, and the fourth capacitor C4 has a capacitance of 104F.

[0068] Figure 2 The control chip in the control chip 100 is an STM32 series chip. The fourth capacitor C4 is connected in series between the VDD interface and the VSS interface of the control chip. One end of the fourth capacitor C4 connected to the VSS is connected to the first power supply, and the other end connected to the VDD is connected to the ground. Figure 2 The drain of the NMOS transistor Q1 is connected to the second resistor strain gauge R2, and the E and F terminals are connected to the strain bridge. The seventh resistor R7 is a calibration resistor, and its resistance is denoted as r7. The programmable resistor input voltage value is denoted as U R , and the current value is denoted as I R . The reference voltage of the control chip input VREF interface is denoted as U

[0069] The voltage value of the programmable resistor is denoted as U R , and the current value flowing through it is denoted as I R . Therefore, the resistance of the programmable resistor is:

[0070]

[0071] The reference voltage of the VREF interface of the input control chip is amplified by the third operational amplifier U3, the voltage amplification module 400 comprises the third operational amplifier U3, the source of the NMOS tube Q1 is connected with the non-inverting input terminal of the third operational amplifier U3, the inverting input terminal of the third operational amplifier U3 is grounded through the ninth resistor R9, the eighth resistor R8 is connected in series between the inverting input terminal and the output terminal of the third operational amplifier U3, and the output terminal of the third operational amplifier U3 is connected with the VREF interface of the control chip 100. The non-inverting input terminal of the third operational amplifier U3 is also connected with the second power supply VCC2, and the inverting input terminal of the third operational amplifier U3 is also grounded through the third capacitor C3. When the resistance values of the eighth resistor R8 and the ninth resistor R9 are both 5kΩ, the voltage value of the input voltage amplified by the third operational amplifier U3 is:

[0072] V REF =2I R R7

[0073] Supposing that the digital input value of the control chip is D, the STM32 series chip adjusts the DAC module thereon, the STM32 series chip selects 12-bit resolution, and then the output voltage of the VOUT interface, that is, the voltage input by the inverting input terminal of the second operational amplifier U2, is:

[0074]

[0075] The amplification input voltage value of the non-inverting input terminal of the second operational amplifier U2 is:

[0076] V IN =ZU R

[0077] Wherein, Z is the voltage division coefficient of the voltage division module 300, the voltage division module 300 comprises the tenth resistor R10, the eleventh resistor R11 and the twelfth resistor R12 connected in series, the tenth resistor R10 is connected with the output terminal of the first operational amplifier U1, the first end of the twelfth resistor R12 is connected with the eleventh resistor R11, the second end of the twelfth resistor R12 is grounded, and the first end of the twelfth resistor R12 is connected with the non-inverting input terminal of the second operational amplifier U2.

[0078] In an embodiment, the resistance values of the tenth resistor R10, the eleventh resistor R11 and the twelfth resistor R12 are 511kΩ, 750Ω and 250Ω respectively, and then

[0079] Since the non-inverting input terminal of the second operational amplifier is equal to the output voltage of the VOUT interface of the control chip, the programmable resistance value can be obtained as:

[0080] Delta r=D*r7

[0081] Therefore, the step of adjusting the programmable resistance so that the difference between the output voltages measured at any two times is zero comprises changing the resistance value of the programmable resistance by inputting a required numerical value to the control chip. The resistance value of the programmable resistance can be changed by inputting a corresponding digital input value D to the STM32 series chip, and the method is simple and can realize arbitrary resistance value adjustment.

[0082] Further, the step of adjusting the programmable resistance so that the difference between the output voltages measured at any two times is zero comprises changing the resistance value of the programmable resistance by adjusting the resistance value of the seventh resistor R7. The threshold range of the resistance value of the programmable resistance can be adjusted by changing the resistance value of the seventh resistor R7, so that the required resistance value can be quickly and conveniently obtained.

[0083] As can be seen from the above, in the programmable resistance and the resistance strain gauge calibration method based on the programmable resistance provided in the embodiments of the present application, the resistance value of the programmable resistance can be controlled by inputting a corresponding numerical value, which facilitates quick adjustment and control of the resistance value of the programmable resistance. Further, by adjusting the resistance value of the programmable resistance on the strain bridge, the measurement results of the resistance strain gauge under different temperatures for the same pressure are the same, and the average of the resistance values of the programmable resistance is taken as the resistance value of the resistance connected to the strain bridge, which improves the measurement accuracy of the measurement circuit, so that the temperature error of the strain bridge can be reduced.

[0084] The above description is only a description of the preferred embodiments of the present application, and does not limit the scope of the present application in any way. Any modification or change made by a person of ordinary skill in the art based on the above disclosure is within the protection scope of the claims.

Claims

1. A programmable resistance, characterized by, The programmable resistance comprises: a control chip having a VREF interface and a VOUT interface, for outputting a corresponding voltage value from the VOUT interface based on a reference voltage input to the VREF interface, to control the resistance value of the programmable resistance; an NMOS transistor, a source, a drain and a gate of the NMOS transistor being connected with a seventh resistor, a fifth resistor and a sixth resistor respectively, one end of the fifth resistor being connected with the ground, the drain of the NMOS transistor being used for inputting a signal, one end of the seventh resistor being used for outputting a signal, and the other end of the seventh resistor being connected with the ground; a voltage amplification module, an input of the voltage amplification module being connected with the source of the NMOS transistor, and an output of the voltage amplification module being connected with the VREF interface; an isolation module, an input of the isolation module being connected with one end of the fifth resistor close to the NMOS transistor, and an output of the isolation module being further connected with a voltage division module; a second operational amplifier, a non-inverting input of the second operational amplifier being connected with an output of the voltage division module, an inverting input of the second operational amplifier being connected with the VOUT interface, and an output of the second operational amplifier being connected with one end of the sixth resistor away from the NMOS transistor, and a second capacitor being connected in series between the inverting input and the output of the second operational amplifier.

2. The programmable resistance of claim 1, wherein, The voltage amplification module comprises a third operational amplifier, the source of the NMOS transistor being connected with a non-inverting input of the third operational amplifier, an inverting input of the third operational amplifier being connected with the ground through a ninth resistor, an eighth resistor being connected in series between the inverting input and an output of the third operational amplifier, and the output of the third operational amplifier being connected with the VREF interface.

3. The programmable resistance of claim 2, wherein, The non-inverting input of the third operational amplifier is further connected with a second power supply, and the inverting input of the third operational amplifier is further connected with the ground through a third capacitor.

4. The programmable resistance of claim 1, wherein, The isolation module comprises a first operational amplifier, a non-inverting input of the first operational amplifier being connected with one end of the fifth resistor close to the NMOS transistor, an inverting input of the first operational amplifier being connected with an output of the first operational amplifier, the non-inverting input of the first operational amplifier being further connected with a third power supply, and the inverting input of the first operational amplifier being further connected with the ground through a first capacitor.

5. The programmable resistance of claim 4, wherein, The voltage division module comprises a tenth resistor, an eleventh resistor and a twelfth resistor connected in series, the tenth resistor being connected with the output of the first operational amplifier, a first end of the twelfth resistor being connected with the eleventh resistor, a second end of the twelfth resistor being connected with the ground, and the first end of the twelfth resistor being connected with the non-inverting input of the second operational amplifier.

6. A method of calibrating a resistance strain gauge based on a programmable resistance, characterized by, The programmable resistance comprises: providing a strain bridge to be measured, the strain bridge being connected with a constant current source, and a negative electrode of the constant current source being connected with the ground, wherein each bridge arm of the strain bridge is provided with a resistance strain gauge, and the resistance strain gauge on one bridge arm is further connected with the programmable resistance in series. applying the same pressure value to each of the resistance strain gauges, measuring the output voltage of the strain bridge at at least three different temperature values; adjusting the programmable resistance to make the difference between any two measured output voltages zero, and recording the resistance value of the programmable resistance; taking the average of the recorded resistance values of the programmable resistance as the resistance value of the strain bridge.

7. The programmable resistance based strain gauge calibration method of claim 6, wherein, applying the same pressure value to each of the resistance strain gauges, measuring the output voltage of the strain bridge at at least three different temperature values; 8. The programmable resistance based strain gauge calibration method of claim 6, wherein, adjusting the programmable resistance to make the difference between any two measured output voltages zero, and recording the resistance value of the programmable resistance; 9. The programmable resistance based strain gauge calibration method of claim 6, wherein, adjusting the programmable resistance to make the difference between any two measured output voltages zero, and recording the resistance value of the programmable resistance; 10. The programmable resistance based strain gauge calibration method of claim 6, wherein, adjusting the programmable resistance to make the difference between any two measured output voltages zero, and recording the resistance value of the programmable resistance; adjusting the programmable resistance to make the difference between any two measured output voltages zero, and recording the resistance value of the programmable resistance; adjusting the programmable resistance to make the difference between any two measured output voltages zero, and recording the resistance value of the programmable resistance; adjusting the programmable resistance to make the difference between any two measured output voltages zero, and recording the resistance value of the programmable resistance;

Images