Resistance measuring system and method of resistance type gas sensing element

Abstract

The invention relates to a resistance measurement system and method for a resistance type gas sensing element, belongs to the technical field of gas sensing elements, and solves the problem of low measurement precision when the resistance of a measured gas sensing element is greatly changed in the prior art. The resistance measuring system comprises a reference voltage generating circuit and a voltage feedback type current source circuit, wherein the reference voltage generating circuit is used for generating constant precision voltage; the voltage feedback type current source circuit comprises an external direct-current power supply, a first operational amplifier, a first MOS (Metal Oxide Semiconductor) tube, a current feedback resistor and a voltage amplifier, and when the resistance of the gas sensing element to be measured is measured, the voltage feedback type current source circuit enables the current flowing through the gas sensing element to be measured to be constant precision current. According to the invention, the resistance measurement of the gas sensing element in a low-power-consumption state is realized, and the resistance measurement precision when the resistance of the gas sensing element changes is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensor elements, and in particular to a resistance measurement system and method for a resistance-type gas sensor element. Background Art

[0002] Resistive gas sensor element (referred to as gas sensor element) is a gas sensor element. When the target gas molecules in the environment interact with the gas sensor element, the resistance of the gas sensor element itself changes significantly. The degree of this change is a measure of the number and enrichment (concentration) of the target gas molecules in the environment. The gas concentration is measured by quantitatively detecting the change in resistance. Resistive gas sensor elements are generally manufactured based on MEMS technology. They are mainly composed of substrates, electrodes and thin layers of gas-sensitive materials. Under normal temperature and clean air conditions, their conductivity is mainly determined by the thin layer of gas-sensitive materials. For gas sensor elements with good conductivity, their own temperature is greatly affected by the working current. Therefore, when detecting their resistance, in order not to affect the detection accuracy of the gas sensor element itself, its working current must be limited to a very low level to ensure that the power dissipated by the gas sensor element itself does not cause a significant increase in its temperature.

[0003] Among them, a type of gas sensor element with good conductivity has a small resistance (for example, tens of ohms) in the normal state (initial state), and its resistance can be greatly increased (for example, tens of kiloohms) as the environment changes. In the prior art, in order to achieve the measurement of the tiny resistance of this type of gas sensor element, one method is voltage divider measurement, in which one or more matching resistors of a certain resistance value are connected in series with the gas sensor element, and the resistance of the gas sensor element is calculated by measuring the voltage divider; another method is current source series measurement, in which a certain current is generated by a current source and flows through the gas sensor element, and then the voltage across the gas sensor element is directly measured, and the resistance of the gas sensor element is directly calculated through the voltage-current relationship. However, both methods have certain defects, resulting in low accuracy in resistance measurement. Specifically, the voltage divider measurement method requires that the resistance of the voltage divider resistor and the gas sensor element are similar, otherwise the accuracy of voltage sampling will be significantly reduced. However, when the resistance of the gas sensor element itself is small (for example, tens of ohms), if the voltage divider resistor is also in the same order of magnitude, the total voltage after series connection must be extremely low, otherwise the power dissipated on the gas sensor element will significantly increase its temperature. On the one hand, it is difficult to achieve an extremely low high-precision voltage source. On the other hand, the absolute value of the voltage across the gas sensor element is still low, which is still not conducive to high-precision voltage acquisition. When measuring by current source series, a smaller working current needs to be generated to flow through the gas sensor element. When the resistance of the gas sensor element becomes very large due to interaction with gas molecules, the current source cannot maintain a fixed current output, which easily causes voltage saturation (the voltage divider on the gas sensor element reaches the power supply voltage). Therefore, the current generated by the current source must be reduced as much as possible while ensuring accuracy to adapt to the situation when the resistance of the gas sensor element increases significantly. However, significantly reducing the output current of the current source will also cause the voltage across the two ends to be low when the resistance of the gas sensor element is low (initial state), which is also not conducive to high-precision voltage acquisition, thereby affecting the overall test accuracy. Summary of the invention

[0004] In view of the above analysis, the embodiments of the present invention aim to provide a resistance measurement system and method for a resistive gas sensor element, so as to solve the technical problem in the prior art that the measurement accuracy is low when the resistance of the measured gas sensor element changes significantly.

[0005] In one aspect, an embodiment of the present invention provides a resistance measurement system for a resistive gas sensor element, the system comprising: a reference voltage generating circuit and a voltage feedback current source circuit,

[0006] A reference voltage generating circuit for generating a constant precision voltage;

[0007] The voltage feedback current source circuit includes: an external DC power supply, a first operational amplifier, a first MOS tube, a current feedback resistor and a voltage amplifier.

[0008] The external DC power supply, the source and drain of the first MOS tube, the current feedback resistor and the gas sensor element to be measured are connected in series in sequence to form a loop, the output end of the first operational amplifier is connected to the gate of the first MOS tube, the constant precision voltage generated by the reference voltage generating circuit is input to one input end of the first operational amplifier, the two input ends of the voltage amplifier are connected to the two ends of the current feedback resistor, and the output end of the voltage amplifier is connected to the other input end of the first operational amplifier.

[0009] Wherein, when measuring the resistance of the gas sensor element to be measured, the current flowing through the gas sensor element to be measured is made to be a constant precision current by setting the differential mode gain of the voltage amplifier.

[0010] Based on further improvement of the above system, the precision current is a micro-milliampere level current.

[0011] Based on further improvement of the above system, the first MOS tube is an N-MOS tube or a P-MOS tube.

[0012] Based on a further improvement of the above system, a current-limiting resistor is arranged between the output end of the first operational amplifier and the gate of the first MOS tube.

[0013] Based on the further improvement of the above system, the reference voltage generating circuit includes: an external DC power supply, a reference voltage source, a second operational amplifier, and a second MOS tube.

[0014] The external DC power supply is respectively connected to the drain of the second MOS tube and the input end of the reference voltage source, the output end of the reference voltage source is connected to one input end of the second operational amplifier, the output end of the second operational amplifier is connected to the gate of the second MOS tube, and the source of the second MOS tube is connected to the other input end of the second operational amplifier;

[0015] The voltage of the gate of the second MOS tube is output as a constant precision voltage generated by the reference voltage generating circuit.

[0016] Based on further improvement of the above system, the second MOS tube is an N-MOS tube or a P-MOS tube.

[0017] Based on the further improvement of the above system, the system further comprises: a plurality of voltage proportional amplification modules with different amplification factors,

[0018] The input end of each voltage proportional amplification system is respectively connected to the two ends of the gas sensor element to be measured, so that the voltage at the two ends of the gas sensor element to be measured is amplified by different amplification factors and then output.

[0019] Based on further improvement of the above system, the voltage proportional amplification module includes an instrument amplifier or a current mirror.

[0020] On the other hand, an embodiment of the present invention provides a method for measuring the resistance of a resistive gas sensor element, the method comprising:

[0021] A reference voltage generating circuit is constructed for generating a constant precision voltage;

[0022] Constructing a voltage feedback current source circuit: connecting the external DC power supply, the source and drain of the first MOS tube, the current feedback resistor and the gas sensor element to be measured in series in sequence to form a loop, connecting the output end of the first operational amplifier to the gate of the first MOS tube, inputting the constant precision voltage generated by the reference voltage generating circuit into one input end of the first operational amplifier, connecting the two input ends of the voltage amplifier to the two ends of the current feedback resistor, and connecting the output end of the voltage amplifier to the other input end of the first operational amplifier;

[0023] Measuring the voltage at both ends of the gas sensor element to be measured: by setting the differential mode gain of the voltage amplifier so that the current flowing through the gas sensor element to be measured is a constant precision current, and then collecting the voltage at both ends of the gas sensor element to be measured;

[0024] Calculating the resistance value of the gas sensor element to be measured: Calculating the resistance value of the gas sensor element to be measured according to the collected voltage across the two ends of the gas sensor element to be measured.

[0025] Based on the further improvement of the above method, the resistance value of the gas sensor element to be measured is calculated according to the following formula:

[0026] R sensor =V sensor / I g ;

[0027] I g =V ref / (G×R g );

[0028] In the formula, R sensor is the resistance value of the gas sensor element to be measured, V sensor is the voltage across the gas sensor element to be tested, I g is the current flowing through the gas sensor element to be measured, V ref is the constant precision voltage generated by the reference voltage generation circuit, G is the differential mode gain of the voltage amplifier, R g is the resistance value of the current feedback resistor.

[0029] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0030] 1. In the voltage feedback current source circuit of the present invention, the first operational amplifier and the first MOS tube cooperate to form negative feedback of the voltage at the positive and negative input terminals of the first operational amplifier. By adjusting the differential mode gain of the voltage amplifier, the voltages at the two input terminals of the first operational amplifier can be made equal, that is, the voltage output by the voltage amplifier is equal to the constant precision voltage generated by the reference voltage generating circuit. At the same time, the voltage output by the voltage amplifier is the voltage across the current feedback resistor after amplification. According to the voltage-current relationship, it can be known that the current flowing through the current feedback resistor is a constant precision current, that is, a constant precision current is provided for the gas sensor element to be measured, thereby realizing the resistance measurement of the gas sensor element working in a low power consumption state, without causing a significant increase in the temperature of the gas sensor element during the measurement process, and ensuring the resistance measurement accuracy when the resistance of the gas sensor element changes.

[0031] 2. In the reference voltage generating circuit of the present invention, when the voltages at the two input terminals of the second operational amplifier are different, the second operational amplifier amplifies the differential mode voltage of the two input terminals and outputs it to the gate of the second MOS tube, so that the voltage between the drain and the source of the second MOS tube changes, and finally the second operational amplifier makes the power supplies of the two input terminals equal, thereby achieving circuit balance by negative feedback. The voltage of the source of the second MOS tube output by the reference voltage generating circuit is equal to the output voltage of the reference voltage source. At the same time, an external DC power supply is provided in the reference voltage generating circuit so that it has a large load driving capability, thereby ensuring the generation of a constant precision voltage.

[0032] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0034] Figure 1 Schematic diagram of the structure of a voltage feedback current source circuit according to an embodiment of the present invention;

[0035] Figure 2 is a schematic structural diagram of a reference voltage generating circuit according to an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the structure of a plurality of voltage ratio amplification modules with different amplification factors according to an embodiment of the present invention;

[0037] Figure 4 Schematic diagram of the circuit structure of the instrument amplifier according to an embodiment of the present invention;

[0038] Figure 5 is a schematic structural diagram of a current source according to an embodiment of the present invention;

[0039] Figure 6 The schematic diagram of the circuit structure for realizing voltage amplification based on an operational amplifier according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0041] A specific embodiment of the present invention discloses a resistance measurement system for a resistive gas sensor element. The system includes: a reference voltage generating circuit and a voltage feedback current source circuit. The reference voltage generating circuit is used to generate a constant precision voltage. Figure 1 As shown in , the voltage feedback current source circuit includes: an external DC power supply, a first operational amplifier, a first MOS tube, a current feedback resistor and a voltage amplifier, wherein the external DC power supply, the source and drain of the first MOS tube, the current feedback resistor and the gas sensor element (sensor) to be measured are sequentially connected in series to form a loop, the output end of the first operational amplifier is connected to the gate of the first MOS tube, the constant precision voltage generated by the reference voltage generating circuit is input to one input end of the first operational amplifier, the two input ends of the voltage amplifier are connected to the two ends of the current feedback resistor, and the output end of the voltage amplifier is connected to the other input end of the first operational amplifier. When measuring the resistance of the gas sensor element (sensor) to be measured, the current flowing through the gas sensor element (sensor) to be measured is made a constant precision current by setting the differential mode gain of the voltage amplifier.

[0042] Based on a conventional current source, the present invention proposes a precision resistance measurement system and method that ensures that a gas sensor element operates in a low power consumption state, and can meet the resistance measurement requirements when the resistance of the gas sensor element increases from tens of ohms to tens of kiloohms.

[0043] Compared with the prior art, in the voltage feedback current source circuit of the present invention, the negative feedback of the voltage of the positive and negative input terminals of the first operational amplifier is formed by the cooperation of the first operational amplifier and the first MOS tube. By adjusting the differential mode gain of the voltage amplifier, the voltages of the two input terminals of the first operational amplifier can be made equal, that is, the voltage output by the voltage amplifier is equal to the constant precision voltage generated by the reference voltage generating circuit. At the same time, the voltage output by the voltage amplifier is the voltage across the current feedback resistor after amplification. According to the voltage-current relationship, it can be known that the current flowing through the current feedback resistor is a constant precision current, that is, a constant precision current is provided for the gas sensor element (sensor) to be measured, and the resistance measurement of the gas sensor element working in a low power consumption state is realized, and the temperature of the gas sensor element will not be significantly increased during the measurement process, and the resistance measurement accuracy when the resistance of the gas sensor element changes is ensured.

[0044] It should be noted that the resistance-type gas sensor element of the embodiment of the present invention is a gas sensor element with a relatively low resistance in a normal state and a resistance that can be greatly increased as the environment changes. The temperature of such a gas sensor element itself is greatly affected by the working current. Therefore, in order not to affect the detection accuracy of the gas sensor element itself, its working current must be limited to a very low level (generally less than 1 mA, micro-milliampere level) to ensure that the power dissipated by the gas sensor element itself does not cause a significant increase in its temperature.

[0045] During implementation, by reasonably selecting the external DC power supply, the first MOS tube, and reasonably setting the differential mode gain of the voltage amplifier, it can be ensured that when the resistance value of the gas sensor element to be measured changes significantly, the current flowing through the gas sensor element to be measured is stable, and the first MOS tube always works in a safe area and is turned on.

[0046] Specifically, the precision current is a micro-milliampere level current. Further specifically, the precision current has a value range of tens of microamperes to hundreds of microamperes. The current within the above level or value range will not cause a significant temperature rise of the gas sensor element.

[0047] Specifically, the first MOS tube is an N-MOS tube or a P-MOS tube. Figure 1In the voltage feedback current source circuit shown in , the first MOS tube adopts an N-MOS tube, wherein the constant precision voltage generated by the reference voltage generating circuit is input to the non-inverting input terminal of the first operational amplifier, and the output terminal of the voltage amplifier is connected to the inverting input terminal of the first operational amplifier. The first MOS tube can also adopt a P-MOS tube, but the wiring of the P-MOS tube should be different from that of the N-MOS tube, wherein the constant precision voltage generated by the reference voltage generating circuit is input to the inverting input terminal of the first operational amplifier, and the output terminal of the voltage amplifier is connected to the non-inverting input terminal of the first operational amplifier.

[0048] Among them, the first MOS tube can play a role in regulating voltage and current in the voltage feedback current source circuit. Taking the case where the first MOS tube in the voltage feedback current source circuit is an N-MOS tube as an example, in actual use, the source voltage Vs of the first MOS tube cannot be higher than the drain voltage Vd, because as the current Ids between the drain and the source increases, the voltage Vds between the drain and the source will decrease, but when it decreases to the point where the conduction condition is not met, the current Ids between the drain and the source cannot continue to increase, so the voltage Vds between the drain and the source will eventually be a relatively small voltage.

[0049] Specifically, the voltage amplifier is an instrumentation amplifier.

[0050] Preferably, in order to implement overcurrent protection for the first operational amplifier, a current limiting resistor is provided between the output end of the first operational amplifier and the first MOS tube.

[0051] Preferably, in order to implement overcurrent protection for the second operational amplifier, a current limiting resistor is also provided between the output terminal of the voltage amplifier and the corresponding input terminal of the first operational amplifier.

[0052] In one embodiment, Figure 2 As shown in, the reference voltage generating circuit includes: an external DC power supply, a reference voltage source, a second operational amplifier, and a second MOS tube, the positive electrode of the external DC power supply is respectively connected to the drain of the second MOS tube and the input end of the reference voltage source, the output end of the reference voltage source is connected to an input end of the second operational amplifier, the output end of the second operational amplifier is connected to the gate of the second MOS tube, and the source of the second MOS tube is connected to the other input end of the second operational amplifier; wherein the voltage of the source of the second MOS tube is output as a constant precision voltage generated by the reference voltage generating circuit.

[0053] In the reference voltage generating circuit of the embodiment of the present invention, when the voltages of the two input terminals of the second operational amplifier are different, the second operational amplifier amplifies the differential mode voltage of the two input terminals and outputs it to the gate of the second MOS tube, so that the voltage between the drain and the source of the second MOS tube changes, thereby changing the voltage of the input terminal connected to the source of the second MOS tube in the second operational amplifier, and finally making the second operational amplifier equal to the power supply of the two input terminals, thereby achieving circuit balance by negative feedback, and the voltage of the source of the second MOS tube outputted by the reference voltage generating circuit is equal to the output voltage of the reference voltage source, and at the same time, an external DC power supply is provided in the reference voltage generating circuit so that it has a large load driving capability, thereby ensuring the generation of a constant precision voltage.

[0054] Specifically, the second MOS tube is an N-MOS tube or a P-MOS tube. Figure 2 In the reference voltage generating circuit shown in , the second MOS tube adopts an N-MOS tube, wherein the output end of the reference voltage source is connected to the non-inverting input end of the second operational amplifier, and the source of the N-MOS tube is connected to the inverting input end of the second operational amplifier. The second MOS tube may also adopt a P-MOS tube, but the wiring of the P-MOS tube should be different from that of the N-MOS tube, specifically: the output end of the reference voltage source is connected to the inverting input end of the second operational amplifier, and the source of the P-MOS tube is connected to the positive phase input end of the second operational amplifier.

[0055] also, Figure 2 The load in the reference voltage generating circuit shown in FIG. 1 is a virtual load, which represents the load driven by its output voltage, or represents Figure 1 The overall resistance of the voltage feedback current source circuit in .

[0056] It should be noted that when the reference voltage generating circuit is working, it is necessary to ensure that the second MOS tube always works in the safe area and is turned on.

[0057] Considering that when the resistance of the gas sensor element to be measured is very small, such as tens of ohms, the voltage across the gas sensor element to be measured is also very small, and the accuracy of directly collecting the voltage across the two ends is poor at this time. Therefore, the voltage across the two ends of the gas sensor element to be measured can be amplified before being collected to adapt to the high-precision collection range of the voltage collection circuit.

[0058] When the resistance of the gas sensor to be tested is relatively large, for example, when the gas sensor to be tested has responded to a specific gas, the voltage across its two ends has already met the range of high-precision voltage acquisition, and it can be directly acquired. It should be noted that when the resistance of the gas sensor to be tested continues to increase, eventually, the voltage of the gas sensor to be tested and the voltage across the current feedback resistor will be very close to the voltage of the N-MOS drain, which is the working limit range of the entire system.

[0059] In one embodiment, the system further includes: a voltage proportional amplification module, wherein the input end of the voltage proportional amplification system is connected to both ends of the gas sensor element to be measured, so that the voltage across both ends of the gas sensor element to be measured is amplified and then output.

[0060] In this embodiment, accurate resistance measurement within a larger resistance variation range can be achieved through the voltage proportional amplification module.

[0061] In a preferred embodiment, Figure 3 As shown in , the system also includes: a plurality of voltage proportional amplification modules with different amplification factors, and the input end of each voltage proportional amplification system is respectively connected to the two ends of the gas sensor element (sensor) to be measured, so that the voltage at the two ends of the gas sensor element (sensor) to be measured is amplified by different amplification factors and then output.

[0062] In this embodiment, multiple voltage proportional amplification modules are connected in parallel in multiple stages to achieve more precise resistance measurement. Each voltage proportional amplification module is set with a different amplification factor to cover the complete resistance variation range of the gas sensor element with a reasonable step size.

[0063] Specifically, the voltage proportional amplification module includes an instrument amplifier or a current mirror.

[0064] When the voltage proportional amplifier module uses an instrument amplifier, Figure 4 As shown in , G is the differential mode gain of the instrumentation amplifier, Vsensor is the voltage across the gas sensor element (sensor) to be measured, and Vsensor-amp is the amplified voltage, where Vsensor-amp = Vsensor × G. At this time, the error is mainly composed of the bias voltage at the input of the instrumentation amplifier and the gain error. In addition, it is necessary to ensure that the amplified voltage Vsensor-amp is still less than the power supply voltage of the instrumentation amplifier.

[0065] When the voltage proportional amplifier module uses a current mirror, Figure 5As shown in the figure, Vsensor is the voltage across the gas sensor element (sensor) to be measured, and Vsensor-amp is the amplified voltage. Assuming R2=R3, R4=K×R1, then Vsensor-amp=Vsensor×K. The error of the system is almost only determined by the bias error Voffset of the in-phase / inverting input terminal of the operational amplifier, except for the error of the proportional relationship between the resistors. Therefore, high-precision voltage proportional amplification can be achieved, and it is only necessary to ensure that the P-MOS and N-MOS in the current mirror circuit work in the safe area.

[0066] The voltage proportional amplifier module can also be built based on traditional operational amplifiers, such as Figure 6 As shown in , Vsensor-amp=Vsensor×R2 / R1. However, since the bias voltage at the input of the operational amplifier will be amplified along with the ratio, the resistance measurement accuracy may be reduced.

[0067] In addition, the voltage across the gas sensor element (sensor) to be measured is collected by an external data acquisition system (such as a measurement circuit, an MCU calculation unit, etc.).

[0068] Preferably, the output end of the reference voltage generating circuit is connected to the data acquisition system, wherein the reference voltage generating circuit can generate a constant precision voltage as a power supply voltage or a reference voltage of the data acquisition system.

[0069] On the other hand, an embodiment of the present invention provides a method for measuring the resistance of a resistive gas sensor element, the method comprising:

[0070] Step 1, constructing a reference voltage generating circuit for generating a constant precision voltage;

[0071] Step 2, constructing a voltage feedback current source circuit: connecting the external DC power supply, the source and drain of the first MOS tube, the current feedback resistor and the gas sensor element (sensor) to be measured in series in sequence to form a loop, connecting the output end of the first operational amplifier to the gate of the first MOS tube, inputting the constant precision voltage generated by the reference voltage generating circuit to one input end of the first operational amplifier, connecting the two input ends of the voltage amplifier to the two ends of the current feedback resistor, and connecting the output end of the voltage amplifier to the other input end of the first operational amplifier;

[0072] Step 3, measuring the voltage at both ends of the gas sensor element to be measured: by setting the differential mode gain of the voltage amplifier so that the current flowing through the gas sensor element to be measured is a constant precision current, and then collecting the voltage at both ends of the gas sensor element to be measured;

[0073] Step 4, calculating the resistance value of the gas sensor element to be measured: calculating the resistance value of the gas sensor element to be measured according to the collected voltage across the two ends of the gas sensor element to be measured.

[0074] In step 4, the resistance value of the gas sensor to be tested is calculated according to the following formula:

[0075] R sensor =V sensor / I g ;

[0076] I g =V ref / (G×R g );

[0077] In the formula, R sensor is the resistance value of the gas sensor to be measured, V sensor is the voltage across the gas sensor to be tested, I g is the current flowing through the gas sensor to be measured, V ref is the constant precision voltage generated by the reference voltage generation circuit, G is the differential mode gain of the voltage amplifier, R g is the resistance value of the current feedback resistor.

[0078] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0079] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A resistance measurement system for a resistive gas sensor element, characterized in that: The system comprises: a reference voltage generating circuit and a voltage feedback current source circuit, A reference voltage generating circuit for generating a constant precision voltage; The voltage feedback current source circuit includes: an external DC power supply, a first operational amplifier, a first MOS tube, a current feedback resistor and a voltage amplifier. The external DC power supply, the source and drain of the first MOS tube, the current feedback resistor and the gas sensor element to be measured are connected in series in sequence to form a loop, the output end of the first operational amplifier is connected to the gate of the first MOS tube, the constant precision voltage generated by the reference voltage generating circuit is input to one input end of the first operational amplifier, the two input ends of the voltage amplifier are connected to the two ends of the current feedback resistor, and the output end of the voltage amplifier is connected to the other input end of the first operational amplifier. Wherein, when measuring the resistance of the gas sensor element to be measured, the current flowing through the gas sensor element to be measured is made to be a constant precision current by setting the differential mode gain of the voltage amplifier.

2. The resistance measurement system according to claim 1, characterized in that: The precision current is a micro-milliampere level current.

3. The resistance measurement system according to claim 1 or 2, characterized in that: The first MOS tube is an N-MOS tube or a P-MOS tube.

4. The resistance measurement system according to claim 1 or 2, characterized in that: A current limiting resistor is arranged between the output end of the first operational amplifier and the gate of the first MOS tube.

5. The resistance measurement system according to claim 1 or 2, characterized in that: The reference voltage generating circuit comprises: an external DC power supply, a reference voltage source, a second operational amplifier, and a second MOS tube. The external DC power supply is respectively connected to the drain of the second MOS tube and the input end of the reference voltage source, the output end of the reference voltage source is connected to one input end of the second operational amplifier, the output end of the second operational amplifier is connected to the gate of the second MOS tube, and the source of the second MOS tube is connected to the other input end of the second operational amplifier; The voltage at the source of the second MOS tube is output as a constant precision voltage generated by the reference voltage generating circuit.

6. The resistance measurement system according to claim 5, characterized in that: The second MOS tube is an N-MOS tube or a P-MOS tube.

7. The resistance measurement system according to claim 1 or 2, characterized in that: The system further comprises: a plurality of voltage proportional amplification modules with different amplification factors, The input end of each voltage proportional amplification system is respectively connected to the two ends of the gas sensor element to be measured, so that the voltage at the two ends of the gas sensor element to be measured is amplified by different amplification factors and then output.

8. The resistance measurement system according to claim 1 or 2, characterized in that: The voltage proportional amplification module includes an instrument amplifier or a current mirror.

9. A method for measuring the resistance of a resistance-type gas sensor element, characterized in that: The method comprises: A reference voltage generating circuit is constructed for generating a constant precision voltage; Constructing a voltage feedback current source circuit: connecting the external DC power supply, the source and drain of the first MOS tube, the current feedback resistor and the gas sensor element to be measured in series in sequence to form a loop, connecting the output end of the first operational amplifier to the gate of the first MOS tube, inputting the constant precision voltage generated by the reference voltage generating circuit into one input end of the first operational amplifier, connecting the two input ends of the voltage amplifier to the two ends of the current feedback resistor, and connecting the output end of the voltage amplifier to the other input end of the first operational amplifier; Measuring the voltage at both ends of the gas sensor element to be measured: by setting the differential mode gain of the voltage amplifier so that the current flowing through the gas sensor element to be measured is a constant precision current, and then collecting the voltage at both ends of the gas sensor element to be measured; Calculating the resistance value of the gas sensor element to be measured: Calculating the resistance value of the gas sensor element to be measured according to the collected voltage across the two ends of the gas sensor element to be measured.

10. The resistance measuring method according to claim 9, characterized in that: The resistance value of the gas sensing element to be measured is calculated according to the following formula: R sensor =V sensor / I g ; I g =V ref / (G×R g ); In the formula, R sensor is the resistance value of the gas sensor element to be measured, V sensor is the voltage across the gas sensor element to be tested, I g is the current flowing through the gas sensor element to be measured, V ref is the constant precision voltage generated by the reference voltage generation circuit, G is the differential mode gain of the voltage amplifier, R g is the resistance value of the current feedback resistor.

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