CN109856336B

CN109856336B - Method for determining optimal working current of MEMS methane sensor

Info

Publication number: CN109856336B
Application number: CN201910148891.8A
Authority: CN
Inventors: 马洪宇; 杜亚娜; 孔祥林; 陈鹏; 丁恩杰
Original assignee: China University of Mining and Technology CUMT
Current assignee: China University of Mining and Technology CUMT
Priority date: 2019-02-28
Filing date: 2019-02-28
Publication date: 2020-07-03
Anticipated expiration: 2039-02-28
Also published as: CN109856336A

Abstract

The invention discloses a method for determining the optimal working current of an MEMS methane sensor, which comprises the following steps: setting initial current, stepping current and termination current of a current source for supplying power to the MEMS methane sensor, scanning and measuring obtained I-V data, and obtaining the data according to ohm's lawCurrent-resistance (I-R) data of the secondary measurement; repeating the test until a maximum resistance value appears, and recording the I-V data obtained by the measurement as complete I-V data; finding the maximum voltage difference value in the complete I-V data, and recording the current corresponding to the maximum voltage difference value as the optimal working current I_W. The method can determine the optimal working current of the MEMS methane sensor, so that the MEMS methane sensor is in the optimal working state, and the MEMS methane sensor outputs the optimal sensitivity.

Description

Method for determining optimal working current of MEMS methane sensor

Technical Field

The method of the invention relates to an MEMS methane sensor, in particular to the working state of the MEMS methane sensor, namely the MEMS methane sensor has good sensitivity, and the method of the invention can lead the MEMS methane sensor to be in the best working state and the output sensitivity to reach the maximum, thereby realizing the optimization of the performance of the sensor.

Background

In the previous invention patents, the MEMS methane sensor based on the silicon heater and the preparation method and application thereof (2014106070934), the all-silicon MEMS methane sensor and the gas detection application and preparation method (2014106070313), the MEMS methane sensor and the application and preparation method thereof (201410606852.5), the methane sensor based on a single heating element and the preparation method and application thereof (2014106059954) provide the MEMS methane sensor. In practical use, it is necessary to provide a suitable current for driving the MEMS methane sensor to operate, and the performance, especially the sensitivity, of the MEMS methane sensor is related to the applied driving current, i.e. the operating state. That is, for the MEMS methane sensor, it is necessary to provide a proper driving current before measuring the gas concentration so that the MEMS methane sensor is in an optimal operating state. I.e. to be able to produce the maximum sensitivity, a corresponding operating current, which is the optimum operating current for sensing, needs to be determined and applied. On the other hand, mass production of MEMS methane sensors has the problem of quality consistency, and the performance of the MEMS methane sensors and their parameters inevitably has differences, so it is necessary to determine the optimal operating current of each MEMS methane sensor to make each MEMS methane sensor in the optimal operating state. The method can analyze and control the performance index of the MEMS methane sensor, thereby ensuring the performance index of the methane sensor and a methane sensor instrument, and providing technical reference in the aspect of performance index control specification for the production of the sensor.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the discreteness of the performances of the sensors in batch production and the requirement of ensuring the sensors to obtain the maximum sensitivity, the invention provides a method for determining the working current of the MEMS methane sensors, namely a method for determining the working point of the MEMS methane sensors, which can ensure the sensors to generate the maximum sensitivity when working and provide standard reference for the production of the sensors

The technical scheme is as follows:

a method for determining the optimal working current of an MEMS methane sensor is realized by adopting an MEMS methane sensor measuring circuit, the circuit comprises a current source, a voltmeter, the MEMS methane sensor and a computer, wherein the current source provides current for the MEMS methane sensor, the voltmeter measures the voltage generated after the MEMS methane sensor is electrified with the current, the positive end of the terminal of the voltmeter and the current outflow end of the current source are connected with one end of the MEMS methane sensor, and the negative end of the terminal of the voltmeter and the current inflow end of the current source are connected with the other end of the MEMS methane sensor; the current source is connected with the voltmeter and the computer, the computer controls the magnitude of the current value output by the current source and records the voltage of the voltmeter at the same time, and the measuring steps are as follows:

the first step is as follows: setting the initial current (I) of the current source powering the MEMS methane sensor_S) Step current (I)_Δ) Terminating the current (I)_E) Terminating the current (I)_E) Greater than the initial current (I)_S) Said termination current (I)_E) And initial current (I)_S) Is divided by the step current (I)_Δ) Number of steps for stepping the current (C)_S) Current source starting from the starting current I_SStarting with a step current I_ΔStepping to a termination current I_EThe time length (t) of each current point of (a) is the same;

the second step is that: the current source starts from the initial current (I)_S) Starting with a step current (I)_Δ) Sweep to termination current (I)_E) Finishing the step current scanning as one measurement, measuring the voltage generated on the MEMS methane sensor corresponding to each current by a voltmeter, and recording the applied nth current value IⁿVoltage value V of timeⁿ，IⁿHas a size of I_S+nI_ΔWherein the sequence number n is from 0 to C_SIs measured for the first time, a smaller value of the terminating current (I) is selected_E) Obtaining current-voltage (I-V) data of the measurement;

the third step: calculating each current value (I) according to ohm's law according to I-V data obtained by scanning and measuring in the second stepⁿ) Corresponding resistance value (R)ⁿ) Obtaining current-resistance (I-R) data of the measurement;

the fourth step: determining the resistance value (R) in the I-R dataⁿ) Whether or not to follow the applied current value (I)ⁿ) Monotonically increasing if the resistance value (R)ⁿ) Dependent current value (I)ⁿ) Monotonically increasing, increasing the number of current steps, i.e. selecting a larger termination current (I)_E) And repeating the second to third steps to perform a plurality of tests, wherein the time interval between two adjacent measurements is not less than 1 minute, and the time interval between two adjacent measurements is kept the same until the resistance value (R)ⁿ) No longer follows the current value (I)ⁿ) Increasing but decreasing along with the increase of the current, namely, generating a maximum resistance value, recording the I-V data obtained by the measurement as complete I-V data, and taking the step number of the corresponding current when the maximum resistance value occurs as C_S，；

The fifth step: using the complete I-V data in the fourth step, each step current (I) is calculated in turn starting from the 1 st step current_Δ ^k) Corresponding voltage difference (V)_Δ ^k) Voltage difference (V)_Δ ^k) Is to calculate the kth current (I)^k) Voltage of time (V)^k) With the (k-1) th current (I)^k-1) Voltage of time (V)^k-1) The difference between the voltages, i.e. V_Δ ^k＝V^k-V^k-1When k is from 1 to C_SAnd k is an integer, when k is 1, V^k-1＝V⁰Is the initial current (I)_S) A corresponding voltage;

and a sixth step: finding the maximum voltage difference (V) in the complete I-V data_Δ ^max) Recording the maximum voltage difference (V)_Δ ^max) The corresponding current is the current (I) corresponding to the mth step current^m＝I_S+mI_Δ) Selecting this current (I)^m) Optimum operating current I for MEMS methane sensor_WI.e. the operating current required to be applied when the MEMS methane sensor is at the optimum operating point is I_WThe sensitivity of methane output can be maximized.

the first step is as follows: setting the initial current (I) of the current source powering the MEMS methane sensor_S) Step current (I)_Δ) Terminating the current (I)_E) Terminating the current (I)_E) Greater than the initial current (I)_S) Said termination current (I)_E) And initial current (I)_S) Is divided by the step current (I)_Δ) Total number of steps for stepping current (C)_S) Current source starting from the starting current I_SStarting with a step current (I)_Δ) Stepping to a termination current I_EThe time length (t) of each current point of (a) is the same;

the third step: calculating the voltage difference (V) of the I-V data of the current round_Δ ^k) Specifically, each step current (I) is calculated in turn from the 1 st step current_Δ ^k) Corresponding voltage difference (V)_Δ ^k) Said voltage difference (V)_Δ ^k) Is to calculate the kth current (I)^k) Voltage of time (V)^k) With the (k-1) th current (I)^k-1) Voltage of time (V)^k-1) Difference in voltage between, V_Δ ^k＝V-^k-V^k-1When k is from 1 to C_SValue and k is an integer, when k is 1, V^k-1＝V⁰Is the initial current (I)_S) The corresponding voltage;

the fourth step: judging whether the voltage difference value (V) along with the increase of the current in the I-V data of the current round_Δ ^k) Maximum value (V)_Δ ^max) Voltage difference (V) as current round I-V data_Δ ^k) Increasing the termination current with a monotonic increase in current, repeating the first to third steps until the voltage difference (V) increases with increasing current_Δ ^k) Maximum value (V)_Δ ^max) To this end, the maximum voltage difference (V) is recorded_Δ ^max) The corresponding current is the current (I) corresponding to the mth step current^m＝I_S+mI_Δ) And selecting this current (I)^m) Optimum operating current I for MEMS methane sensor_WI.e. when applied to a MEMS methane sensorHas a current of I_WThe sensitivity of the output methane is maximum.

Further, the MEMS methane sensor measuring circuit can be replaced by a structure comprising a single chip microcomputer, a DAC converter, a current source chip, an MEMS methane sensor, an impedance conversion unit, a voltage attenuation unit and an ADC circuit which are sequentially connected and form a loop, wherein the single chip microcomputer controls the DAC to output voltage so as to control the current flowing through the MEMS methane sensor, and measurement, voltage data reading, storage and computational analysis of the voltage at two ends of the sensing element are realized.

Has the advantages that: the method for determining the optimal working current of the MEMS methane sensor can accurately and quickly determine the working current sensed by the MEMS methane sensor through measurement and analysis, thereby well ensuring that the sensor is in a good working state, and enabling the output signal of the sensor to be maximum and the working current to be optimal, namely the best methane gas sensitivity. Theoretically, products in the same batch and the same specification have the same characteristics, and in practice, most characteristics of the products in the same batch and the same specification are relatively close to each other, so that the products can have better consistency and can be interchanged according to certain standards. However, the consistency of the product is poor, and by adopting the method, whether the consistency meets the requirement can be judged by adopting the optimal working current and the maximum voltage difference value of the working current as parameters. Meanwhile, if the device has performance drift after long-time operation, the method for giving compensation by using the optimal working current and the maximum voltage difference value can be adopted, and even whether the device can continue to operate or not can be judged. The safety of the device can be ensured by selecting a smaller terminating current for the first time, the device is prevented from being damaged by a larger current, and the purpose is realized by gradually increasing the current. The method for determining the working current of the MEMS methane sensor provided by the invention uses the current source and the voltmeter which are provided with the computer control interface to be connected with the computer, and the current source and the voltmeter are connected with the MEMS methane sensor.

Drawings

FIG. 1 is a schematic diagram of a first measurement circuit connection for the operating point of a MEMS methane sensor of the present invention;

FIG. 2 is a graph of MEMS methane sensor current versus resistance, voltage, and voltage difference;

FIG. 3 is a schematic diagram of a second measurement circuit for the operating point of the MEMS methane sensor of the present invention;

FIG. 4 is a schematic diagram of the connections between the DAC, current source chip, sensing elements and impedance transformation.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

Embodiment 1, a method for determining an operating current of a MEMS methane sensor is implemented by using a MEMS methane sensor measurement circuit, as shown in fig. 1, the circuit includes a current source, a voltmeter, a MEMS methane sensor, and a computer, the current source provides a current for the MEMS methane sensor, the voltmeter measures a voltage generated after the MEMS methane sensor is energized with the current, a "positive" terminal of a terminal of the voltmeter and a current outflow terminal of the current source are connected to one end of the MEMS methane sensor, and a "negative" terminal of the voltmeter and a current inflow terminal of the current source are connected to the other end of the MEMS methane sensor; the current source is connected with the voltmeter and the computer, and the computer controls the magnitude of the current value output by the current source and records the voltage of the voltmeter at the same time; if a source meter integrating a current source and a voltmeter is used, such as a precision source meter, or an automatic test system integrating a computer, the precision source meter or the automatic test system is connected with the MEMS methane sensor to form a measurement circuit, the computer is connected with the precision source meter and controls the current source of the precision source meter to provide current for the MEMS methane sensor, and a precision source meter voltage measurement unit measures voltage generated after the MEMS methane sensor is electrified with the current;

the first step is as follows: initial current I for selecting current source to power MEMS methane sensor_SStep current I_ΔTerminating the current I_EThe method specifically comprises the following steps:

terminating the current I_EGreater than the initial current I_STerminating the current I_EAnd an initial current I_SIs always the step current I_ΔInteger multiple of (a) ofTerminating the current I_EAnd an initial current I_SIs divided by the step current I_ΔNumber of steps C for stepping the current_S(ii) a Current source applied to MEMS methane sensor at each current point from I_SIs started with_ΔStep to I_EThe time length t of each current point of (a) is the same; when implemented, the initial current I_SIs selected as 0.02mA, step current I_ΔSelected as 0.02mA, the termination current I at the first measurement_ESelected as 1mA, the number of current-stepped steps C at the first measurement_SSetting the time length t to be the same value by adopting a precision source table for 49 steps;

the second step is that: current source starting from the initial current I_SAt the beginning, with a step current I_ΔSweep to termination current I_EFinishing the whole step current scanning into one measurement, measuring the voltage generated on the sensor corresponding to each current by a voltmeter during each measurement, and recording the nth current value I applied to the sensor by the current source by a computer or an automatic test systemⁿVoltage value V of timeⁿ，IⁿHas a size of I_S+nI_ΔWhen n is from 0 to C_SObtaining the value to obtain the current-voltage I-V data of the measurement; selecting a terminating current I with a smaller value when measuring for the first time_EThe subsequent measurement can be made by increasing or decreasing the number of current-stepped steps C_SIncreasing or decreasing the termination current I_E(ii) a The time length t of each measurement is kept the same and set;

the third step: calculating each current value I according to ohm's law according to I-V data obtained by scanning and measuring in the second stepⁿCorresponding resistance value RⁿObtaining the current-resistance I-R data measured at this time;

the fourth step: judging the resistance R in the third step I-R dataⁿWhether or not according to the applied current value IⁿMonotonically increasing if the resistance value RⁿAccording to the current value IⁿMonotonically increasing, increasing the number of current-stepped steps C_SI.e. selecting a larger terminating current I_EAnd repeating the second to third steps to perform a plurality of tests, with a time interval between two adjacent measurementsNot less than 1 minute, the time interval between two adjacent measurements is 2 minutes, and the termination current I is measured for the second time_EThe number of steps C of the corresponding current step which can be taken as 1.4mA_SFor step 69, the termination current I at the time of the third measurement_ENumber of steps C that can be taken as 2mA, corresponding to current step_SFor 99 steps, the step current I_ΔAnd an initial current I_SThe constant value is 0.02mA, so that the termination current I is increased_EMeasuring for several times until the resistance value RⁿNo longer according to current value IⁿIncreasing but decreasing, finding the maximum resistance point, recording the I-V data obtained from this measurement as complete I-V data, and recording the corresponding C_SIs complete C_S，；

The fifth step: using the complete I-V data, calculating each step current I in turn starting from the 1 st step current_Δ ^kCorresponding voltage difference V_Δ ^kVoltage difference V_Δ ^kIs to calculate the kth current I^kVoltage V of time^kWith the (k-1) th current I^k-1Voltage V of time^k-1The difference between the voltages, i.e. V_Δ ^k＝V^k-V^k-1When k is from 1 to perfect C_SValue, when k is 1, V^k-1＝V⁰Is an initial current I_SA corresponding voltage;

and a sixth step: finding the maximum voltage difference V in the complete I-V data_Δ ^maxRecording the maximum voltage difference V_Δ ^maxThe corresponding current is the current (I) corresponding to the mth step current^m＝I_S+mI_Δ) This current I is selected, as shown in FIG. 2^mFor optimum operating current I of the sensor_WI.e. the operating current I to be applied when the sensor is at the optimum operating point_W＝I^mThis maximizes the methane sensitivity of the sensor output.

Example 2: a method for determining the working current of a MEMS methane sensor adopts the same circuit as the embodiment 1, and comprises the following measuring steps:

the first step is as follows: setting the initial current I of the current source for supplying power to the MEMS methane sensor_SStep current I_ΔTerminating the current I_ETerminating the current I_EGreater than the initial current I_SSaid termination current I_EAnd an initial current I_SIs divided by the step current I_ΔTotal number of steps C for stepping current_SCurrent source starting from the starting current I_SStarting with a step current I_ΔStepping to a termination current I_EThe time length t of each current point of (a) is the same;

the second step is that: current source starting from the initial current I_SAt the beginning, with a step current I_ΔSweep to termination current I_EFinishing the step current scanning as one measurement, measuring the voltage generated on the sensor by the voltmeter and corresponding to each current, and recording the nth current value I applied to the sensor by the current sourceⁿVoltage value V of timeⁿ，IⁿHas a size of I_S+nI_ΔWherein n is from 0 to C_SIs measured for the first time, a smaller value of the terminating current I is selected_EObtaining the current-voltage I-V data of the measurement;

the third step: calculating the voltage difference V of the I-V data of the current round_Δ ^kSpecifically, each step current I is calculated in turn from the 1 st step current_Δ ^kCorresponding voltage difference V_Δ ^kSaid voltage difference V_Δ ^kIs to calculate the kth current I^kVoltage V of time^kWith the (k-1) th current I^k-1Voltage V of time^k-1Difference in voltage between, V_Δ ^k＝V^k-V^k-1When k is from 1 to C_SValue and k is an integer, when k is 1, V^k-1＝V⁰Is an initial current I_SA corresponding voltage;

the fourth step: judging whether the voltage difference value V is increased along with the current in the I-V data of the current round_Δ ^kMaximum value V appears_Δ ^maxVoltage difference V as current round I-V data_Δ ^kIncreasing termination with monotonic increase in currentCurrent, repeating the first to third steps until the voltage difference V increases with the current_Δ ^kMaximum value V appears_Δ ^maxUntil now, the maximum voltage difference V is recorded_Δ ^maxThe corresponding current is the current (I) corresponding to the mth step current^m＝I_S+mI_Δ) And selecting this current I^mOptimum operating current I for MEMS methane sensor_WI.e. when the current applied to the MEMS methane sensor is I_WThe sensitivity of the output methane is in the maximum state.

As shown in fig. 3, the measurement circuit is a single chip, a DAC converter, a current source chip, an MEMS methane sensor, an impedance conversion unit, a voltage attenuation unit, and an ADC circuit, which are connected in sequence to form a loop, and the single chip controls the DAC to output a voltage to control a current flowing through the MEMS methane sensor, thereby implementing measurement, voltage data reading, storage, and computational analysis of voltages at two ends of the sensing element. The DAC converter is at least 12 bits; the current source chip adopts LT 3092; the impedance conversion unit adopts LT6023, LT6023-1 or AD 8667; the voltage attenuation unit adopts operational amplifiers such as LT1997-3, LT1997-2 or AD8279 and the like to perform voltage attenuation by 0.25 times; sampling the voltage at two ends of the sensing element after impedance conversion and voltage attenuation by adopting a 24-bit ADC (analog to digital converter) such as ADS124S06/ADS124S 08; the single chip microcomputer controls the DAC to output different currents and controls the ADC to obtain the voltage of the DAC output value under the corresponding current; the DAC can also adopt a DAC module of the singlechip.

Referring to fig. 4 showing a connection diagram among the DAC, the current source chip, the sensing element, and the impedance transformation, In, Out, and Set are three pins of the current source chip LT3092, and the resistance value of the resistor R connected to the Out pin may be 100 ohms, or other resistors may be used.

The above description is only a preferred embodiment of the present invention, and it should be noted that it is obvious to those skilled in the art that several modifications and amendments can be made without departing from the principle of the present invention, such as measuring the current on the element by using a voltage source and calculating the analysis working point according to the measured current, and these modifications and amendments should be considered as the protection scope of the present invention.

Claims

1. A method for determining the optimal working current of an MEMS methane sensor is characterized by being realized by adopting an MEMS methane sensor measuring circuit, wherein the circuit comprises a current source, a voltmeter, the MEMS methane sensor and a computer, the current source provides current for the MEMS methane sensor, the voltmeter measures the voltage generated after the MEMS methane sensor is electrified with the current, the positive end of the terminal of the voltmeter and the current outflow end of the current source are connected with one end of the MEMS methane sensor, and the negative end of the terminal of the voltmeter and the current inflow end of the current source are connected with the other end of the MEMS methane sensor; the current source is connected with the voltmeter and the computer, the computer controls the magnitude of the current value output by the current source and records the voltage of the voltmeter at the same time, and the measuring steps are as follows:

the first step is as follows: setting the initial current I of the current source for supplying power to the MEMS methane sensor_SStep current I_ΔTerminating the current I_ETerminating the current I_EGreater than the initial current I_SSaid termination current I_EAnd an initial current I_SIs divided by the step current I_ΔNumber of steps C for stepping the current_SCurrent source starting from the starting current I_SStarting with a step current I_ΔStepping to a termination current I_EThe time length t of each current point of (a) is the same;

the second step is that: current source starting from the initial current I_SAt the beginning, with a step current I_ΔSweep to termination current I_EFinishing the step current scanning as one measurement, measuring the voltage generated on the MEMS methane sensor corresponding to each current by a voltmeter, and recording the applied nth current value IⁿVoltage value V of timeⁿ，IⁿHas a size of I_S+nI_ΔWherein the sequence number n is from 0 to C_SIs measured for the first time, a smaller value of the terminating current I is selected_EObtaining the current-voltage I-V data of the measurement;

the third step: calculating each current value according to ohm's law according to I-V data obtained by scanning and measuring in the second stepIⁿCorresponding resistance value RⁿObtaining the current-resistance I-R data measured at this time;

the fourth step: determining the resistance value R in the I-R dataⁿWhether or not according to the applied current value IⁿMonotonically increasing if the resistance value RⁿAccording to the current value IⁿMonotonically increasing, increasing the number of current steps, i.e. selecting a larger terminating current I_EAnd repeating the second to third steps to carry out a plurality of tests, wherein the time interval between two adjacent measurements is not less than T minutes, and the time interval between two adjacent measurements is kept the same until the resistance value R is reachedⁿNo longer according to current value IⁿIncreasing but decreasing along with the increase of the current, namely, generating a maximum resistance value, recording the I-V data obtained by the measurement as complete I-V data, and taking the step number of the corresponding current when the maximum resistance value occurs as C_S’；

The fifth step: using the complete I-V data in the fourth step, each step current I is calculated in turn starting from the 1 st step current_ΔCorresponding voltage difference V_Δ ^kVoltage difference V_Δ ^kIs to calculate the kth current I^kVoltage V of time^kWith the (k-1) th current I^k-1Voltage V of time^k-1The difference between the voltages, i.e. V_Δ ^k＝V^k-V^k-1When k is from 1 to C_SAnd k is an integer, when k is 1, V^k-1Is an initial current I_SThe corresponding voltage;

and a sixth step: finding the maximum voltage difference V in the complete I-V data_Δ ^maxRecording the maximum voltage difference V_Δ ^maxThe corresponding current is the current I corresponding to the mth step current^m＝I_S+mI_ΔSelecting this current I^mOptimum operating current I for MEMS methane sensor_WI.e. the operating current required to be applied when the MEMS methane sensor is at the optimum operating point is I_WThe sensitivity of methane output can be maximized.

2. The method for determining the optimal working current of the MEMS methane sensor according to claim 1, wherein in the fourth step, T has a value of 1.

3. A method for determining the optimal working current of an MEMS methane sensor is characterized by being realized by adopting an MEMS methane sensor measuring circuit, wherein the circuit comprises a current source, a voltmeter, the MEMS methane sensor and a computer, the current source provides current for the MEMS methane sensor, the voltmeter measures the voltage generated after the MEMS methane sensor is electrified with the current, the positive end of the terminal of the voltmeter and the current outflow end of the current source are connected with one end of the MEMS methane sensor, and the negative end of the terminal of the voltmeter and the current inflow end of the current source are connected with the other end of the MEMS methane sensor; the current source is connected with the voltmeter and the computer, the computer controls the magnitude of the current value output by the current source and records the voltage of the voltmeter at the same time, and the measuring steps are as follows:

the second step is that: current source starting from the initial current I_SAt the beginning, with a step current I_ΔSweep to termination current I_EFinishing the step current scanning as one measurement, measuring the voltage generated on the sensor by the voltmeter and corresponding to each current, and recording the applied nth current value IⁿVoltage value V of timeⁿ，IⁿHas a size of I_S+nI_ΔWherein the sequence number n is from 0 to C_SIs measured for the first time, a smaller value of the terminating current I is selected_EObtaining the current-voltage I-V data of the measurement;

the third step: calculating the voltage difference V of the I-V data of the current round_Δ ^kSpecifically, each step current I is calculated in turn from the 1 st step current_ΔCorresponding voltage difference V_Δ ^kSaid voltage difference V_Δ ^kIs to calculate the kth current I^kVoltage V of time^kWith the (k-1) th current I^k-1Voltage V of time^k-1Difference in voltage between, V_Δ ^k＝V^k-V^k-1When k is from 1 to C_SValue and k is an integer, when k is 1, V^k-1＝V⁰Is an initial current I_SThe corresponding voltage;

the fourth step: judging whether the voltage difference value V is increased along with the current in the I-V data of the current round_Δ ^kMaximum value V appears_Δ ^maxVoltage difference V as current round I-V data_Δ ^kIncreasing the termination current with the monotonic increase in current, repeating the first to third steps until the voltage difference V increases with the increase in current_Δ ^kMaximum value V appears_Δ ^maxUntil now, the maximum voltage difference V is recorded_Δ ^maxThe corresponding current is the current I corresponding to the mth step current^m＝I_S+mI_ΔAnd selecting this current I^mOptimum operating current I for MEMS methane sensor_WI.e. when the current applied to the MEMS methane sensor is I_WThe sensitivity of the output methane is maximum.

4. The method for determining the optimal working current of the MEMS methane sensor according to claim 1 or 3, wherein the MEMS methane sensor measuring circuit can be replaced by a structure which is a single chip microcomputer, a DAC converter, a current source chip, the MEMS methane sensor, an impedance conversion unit, a voltage attenuation unit and an ADC circuit which are sequentially connected to form a loop, wherein the single chip microcomputer controls DAC output voltage to control current flowing through the MEMS methane sensor, and measurement, voltage data reading, storage and computational analysis of voltage at two ends of a sensing element are achieved.