CN105928989B - Humidity sensor and its correction of temperature drift method based on the huge piezo-resistive arrangement of π type - Google Patents

Abstract

The present invention provides a kind of humidity sensor based on the huge piezo-resistive arrangement of π type, including 4 data collectors, data conversion integrated layer and filter screen, 4 data collector point two rows are distributed on data conversion integrated layer, the filter screen is placed on the detection zone of the data collector, and the data conversion integrated layer includes the very color liquid crystal display of four-point resistance measurement circuit, CS1180 analog-digital converter, STM32F407 single-chip microcontroller and TFT；4 data collectors give collected data to CS1180 analog-digital converter by four-point resistance measurement amount of circuitry circuit transmission, it exports after the conversion of CS1180 analog-digital converter to STM32F407 single-chip microcontroller, the very color liquid crystal display of TFT is sent to by STM32F407 single-chip microcontroller, in the very color liquid crystal display screen display of TFT；In addition, the present invention also provides the correction of temperature drift methods of humidity sensor.

Description

Humidity sensor based on π-type giant piezoresistive structure and its temperature drift correction method

technical field

The invention relates to a humidity sensor based on a π-type giant piezoresistive structure and a temperature drift correction method thereof, belonging to the technical field of micro-nano electromechanical system sensors.

Background technique

Since the 1980s, with the rapid development of MEMS (micro-electromechanical systems) technology, more and more MEMS devices have been widely used in various fields such as industry and agriculture, aerospace, meteorological environment, national defense and military affairs. In recent years, with the successful development of devices such as microprobes and microflow meters, a large number of MEMS devices have entered the fields of chemical analysis, atmospheric detection, and temperature and humidity detection. However, the current humidity sensor cannot achieve real-time high-precision, high-sensitivity, and high-reliability humidity measurement due to the structural limitations of the device itself.

Most traditional humidity sensors use resistive or capacitive humidity sensors to detect the concentration of water vapor in the air. However, since the dielectric constant of water and polymers changes asynchronously with temperature, it is easy to cause temperature drift. At the same time, it is easily affected by light, so it is difficult to achieve high-precision and high-sensitivity measurement of small humidity changes. Therefore, it is necessary to deal with the influence of temperature and the status quo of low sensitivity.

Contents of the invention

In order to solve the above-mentioned defects and deficiencies in the prior art, the present invention provides a humidity sensor based on a π-type giant piezoresistive structure and its temperature drift correction method. The piezoresistive coefficient and gauge coefficient of the humidity sensor both increase by orders of magnitude , which greatly increases the sensitivity of the sensor, can effectively capture small humidity changes in the air, and expand the measurement range.

In order to solve the above technical problems, the present invention provides a humidity sensor based on a π-type giant piezoresistive structure, including 4 data collectors, a data conversion integration layer and a filter screen, and the 4 data collectors are distributed in two rows in the data On the conversion integration layer, the filter screen is placed on the detection area of the data collector, and the data conversion integration layer includes a four-point resistance measurement circuit, a CS1180 analog-to-digital converter, a STM32F407 single-chip microcomputer and a TFT true-color liquid crystal display; The 4 data collectors transmit the collected data to the CS1180 analog-to-digital converter through the four-point resistance measurement circuit, and the CS1180 analog-to-digital converter converts and outputs to the STM32F407 microcontroller, which is sent to the TFT true-color LCD display by the STM32F407 microcontroller. Displayed on the true color LCD screen;

The data collector includes a substrate, a stress layer, a detection area and a π-type giant piezoresistive structure, the stress layer is placed on the substrate, and the detection area and the π-type giant piezoresistive structure are distributed on the stress layer , wherein the detection area is placed in the center of the stress layer, there are two π-type giant piezoresistive structures, distributed on both sides of the detection area and at the edge of the stress layer, and the two π-type giant piezoresistive structures The piezoresistive structure is connected in series through a connecting line made of metal aluminum, and powered by a constant current source; the π-type giant piezoresistive structure includes a silicon structure area, a germanium structure area and a gold structure area, wherein the silicon structure area is divided into two sections, divided into Arranged at both ends of the germanium structure region, the gold structure region is placed on the same side of the silicon structure region and the germanium structure region, and the length of the gold structure region is equal to the length of the two silicon structure regions and the germanium structure region The sum of the lengths, the junction of the silicon structure region and the germanium structure region is a silicon-germanium heterojunction, and the junction of the gold structure region and the silicon structure region and germanium structure region is gold-silicon-germanium Heterojunction; the other side of the germanium structure region is provided with a potential monitoring point; one side of the π-type giant piezoresistive structure is provided with a temperature sensor for real-time detection of ambient temperature.

Further, a solid support structure made of monocrystalline silicon is provided between the stress layer and the substrate to prevent the stress layer from being ruptured due to excessive pressure.

Further, a heating device is provided between the stress layer and the solid support structure, and the heating device is a polysilicon resistance wire.

Further, the data collector also includes two common-mode signal compensation structures with the same size and composition materials as the π-type giant piezoresistive structure, and the two common-mode signal compensation structures are located at both ends of the detection area and located at At the edge of the stress layer, a square structure is formed with the two π-type giant piezoresistive structures, and the common-mode signal compensation structure is connected in series with the π-type giant piezoresistive structure through a connecting line made of metal aluminum, and is connected by the same powered by a constant current source.

Further, a U-shaped stress enhancement structure is provided around the π-type giant piezoresistive structure; the stress enhancement structure is a groove-shaped structure etched on the stress layer by RIE etching technology.

Further, the material of the substrate is glass, the material of the stress layer is silicon dioxide, and the material of the detection area is polyimide.

Further, between the four-point resistance measurement circuit and the CS1180 analog-to-digital converter, a multiplexer and an amplification filter circuit connected in sequence are provided; the amplification filter circuit includes resistors R1, R2, R3, R4 and The first-stage amplifying circuit composed of amplifier AD620 is a second-order RC low-pass filter composed of resistor R5 and capacitor C1, resistor R7 and capacitor C2.

Further, the size of the silicon-germanium heterojunction is (60-70) μm*5 μm*(50-150) nm, and the size of the gold-silicon-germanium heterojunction is (60-70) μm*(35- 50)μm*(50-150)nm.

Further, a titanium structure area is provided between the gold structure area, the silicon structure area and the germanium structure area for fixing the gold structure area, and the length of the titanium structure area is equal to the length of the gold structure area.

The present invention also provides a temperature drift correction method for a humidity sensor based on a π-type giant piezoresistive structure, which is characterized in that: the STM32F407 single-chip microcomputer utilizes the quadratic surface fitting function H _standard = f (V, T) to influence the temperature drift Carry out real-time compensation correction, the obtaining method of described quadratic surface fitting function H _standard =f (V, T) comprises the following steps:

Step 1, put the humidity sensor into the constant temperature and humidity test chamber, determine the humidity when the temperature T = 20 degrees as the standard humidity H _standard , and then adjust the temperature in the test chamber, the adjustment range is -20-60 degrees, and the step size is 10 degrees, get the output voltage value V(T) of the humidity sensor at different temperatures;

Step 2, change the standard humidity H _standard , repeat step 1, obtain the output voltage value V (H _standard , T) of the humidity sensor under different temperatures and different humidity, and use the output voltage value V and temperature value T of the humidity sensor as the to-be-built The input variable of the standard humidity surface equation H _standard = (V, T), so the influence of the temperature factor can be taken into account when analyzing the humidity;

Step 3, using the discrete data for constructing the surface equation H _standard =(V, T) measured by the above experiment to carry out quadratic surface fitting, and adopting the least squares method to determine the quadratic surface fitting function H _standard =f(V , T) in the coefficients of the independent variables V and T, so as to determine the quadratic surface fitting function H _standard = f (V, T).

Beneficial technical effects achieved by the present invention: the present invention provides a humidity sensor based on a π-type giant piezoresistive structure. The best organic polymer material polyimide absorbs. Due to the excellent performance of polyimide and the filtering effect of the filter, it can realize the humidity detection work in harsh environments and expand the use range of this humidity sensor. At the same time, the data collector of the sensor adopts a π-type giant piezoresistive structure composed of two silicon-germanium heterojunctions and a gold-silicon-germanium heterojunction, and is fabricated by RIE etching around the π-type giant piezoresistive structure. The stress-enhanced structure can increase the piezoresistive coefficient and gauge coefficient of the humidity sensor by an order of magnitude. Through the combination of two heterojunctions, the π-type giant piezoresistive structure can simultaneously amplify the stress in the horizontal and vertical directions. Larger resistance resistance changes under certain conditions, which fundamentally improves the sensitivity of the humidity sensor; the use of two common-mode signal compensation structures can ensure the measurement accuracy of the pressure sensing structure of the humidity sensor in complex external environments; in order to prevent stress The layer is broken due to excessive stress under the extreme working condition. The humidity sensor is equipped with a solid support structure made of monocrystalline silicon under the stress layer to provide protection for the stress layer under the extreme working conditions, so that the measurement range of the humidity sensor and The application occasions have been expanded; in addition, the sensor adopts the four-point resistance measurement method and the signal amplification and filter conditioning circuit, which can obtain more accurate signals, weaken the influence of external factors such as noise on the detection results, and achieve high precision and stable measurement Effect. The measurement accuracy and stability of the system can be improved by using 4 data collectors to obtain the data and taking the average value. The temperature drift correction method of the humidity sensor provided by the invention can effectively improve the accuracy of detection and avoid the influence of temperature on humidity measurement.

Description of drawings

The structural representation of the data collector of the present invention of Fig. 1;

The structural representation of the π-type giant piezoresistive structure of Fig. 2 of the present invention;

The overall structure schematic diagram of Fig. 3 the present invention;

The amplification filter circuit diagram of Fig. 4 of the present invention;

Fig. 5 schematic diagram of the working process of the humidity sensor of the present invention;

FIG. 6 is a schematic diagram of a method for correcting temperature drift of a humidity sensor according to the present invention.

Among them: 1 substrate; 2 detection area; 3 stress enhancement structure; 4 stress layer; 5π type giant piezoresistive structure; 6 common mode signal compensation structure; 7 solid support structure; 8 silicon structure area; 11 gold structure area; 12 silicon-germanium heterojunction; 13 gold-silicon-germanium heterojunction; 14 heating device; 15 temperature sensor; 16 potential measurement point; 17 data collector; 18 data conversion integration layer; 19 Filter.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing. The following examples are only used to more clearly illustrate the technical scheme of the present invention, and cannot limit the protection scope of the present invention with this.

As shown in Figures 1-5, the present invention provides a humidity sensor based on π-type giant piezoresistive structure, including 4 data collectors 17, data conversion integration layer 18 and filter screen 19, 4 said data collectors 17 Distributed in two rows on the data conversion integration layer 18, the filter screen 19 is placed on the detection area 2 of the data collector 17, and the data conversion integration layer 18 includes a four-point resistance measurement circuit, a CS1180 analog-to-digital converter , STM32F407 single-chip microcomputer and TFT true-color LCD display; 4 data collectors transmit the collected data to the CS1180 analog-to-digital converter through the four-point resistance measurement circuit, and the CS1180 analog-to-digital converter is converted and output to the STM32F407 single-chip microcomputer, which is controlled by the STM32F407 single-chip microcomputer Send to the TFT true color LCD display, and display on the TFT true color LCD display;

The data collector 17 includes a substrate 1, a stress layer 4, a detection region 2 and a π-type giant piezoresistive structure 5, the stress layer 4 is placed on the substrate 1, and the detection region 2 and the π-type giant piezoresistive structure 5 The structure 5 is distributed on the stress layer 4, wherein the detection area 2 is placed in the center of the stress layer 4, and there are two π-type giant piezoresistive structures 5, respectively C1 and C2, distributed in the detection area 2 and at the edge of the stress layer 4, the two π-type giant piezoresistive structures 5 are connected in series through connecting wires made of aluminum, and powered by a constant current source, which provides stable current At the same time, the measurement error caused by different power sources is reduced; the π-type giant piezoresistive structure 5 includes a silicon structure region 8, a germanium structure region 9 and a gold structure region 11, wherein the silicon structure region 8 is divided into two sections, and is distributed in the germanium structure region. The two ends of the structural region 9, the gold structural region 11 is placed on the same side of the silicon structural region 8 and the germanium structural region 9, and the length of the gold structural region 11 is equal to two sections of the silicon structural region 8 and the germanium structural region 9, the junction of the silicon structure region 8 and the germanium structure region 9 is a silicon-germanium heterojunction 12, the gold structure region 11 and the silicon structure region 8, germanium structure region 9 The junction is a gold-silicon-germanium heterojunction 13, in which two silicon-germanium heterojunctions 12 are parallel to each other and perpendicular to the gold-silicon-germanium heterojunction 13, thus forming a π structure, called π-type giant pressure resistance structure 5; the other side of the germanium structure region 9 is provided with a potential monitoring point 6; one side of the π-type giant piezoresistive structure 5 is provided with a temperature sensor 15 for real-time detection of ambient temperature.

The material of the substrate 1 is glass, the material of the stress layer 4 is silicon dioxide, and the material of the detection area 2 is polyimide, which can realize humidity detection in complex environments.

In order to prevent the stress layer 4 from being broken due to excessive pressure under the extreme working condition, a solid support structure 7 made of monocrystalline silicon is provided between the stress layer 4 and the substrate 1, so that the stress layer 4 can withstand the extreme working conditions. Provide protection. A heating device 14 is provided between the stress layer 4 and the solid support structure 7, and the heating device is a polysilicon resistance wire.

A U-shaped stress enhancement structure 3 is provided around the π-type giant piezoresistive structure 5; the stress enhancement structure 3 is a groove-shaped structure etched on the stress layer by RIE etching technology, and the stress is more concentrated, so that the stress changes The resulting deformation is more obvious.

The data collector 17 also includes two common-mode signal compensation structures 6 with the same size and composition materials as the π-type giant piezoresistive structure, respectively C3 and C4, and the two common-mode signal compensation structures 6 are located in the Both ends of the detection area 2 are located at the edge of the stress layer 4, forming a square structure with the two π-type giant piezoresistive structures 5, and the common-mode signal compensation structure 6 and the π-type giant piezoresistive structure 5 Connecting wires made of metal aluminum are connected in series and powered by the same constant current source.

Tests have shown that the size of the π-type giant piezoresistive structure 5 greatly affects the piezoresistivity and gauge factor of the giant piezoresistive structure. In the present invention, the size of the silicon-germanium heterojunction is (60-70) μm*5 μm *(50-150)nm, the size of the gold-silicon-germanium heterojunction is (60-70)μm*(35-50)μm*(50-150)nm.

A titanium structure region 10 is arranged between the gold structure region 11 and the silicon structure region 8 and the germanium structure region 9 for fixing the gold structure region 11, and the length of the titanium structure region 10 is the same as that of the gold structure region 11. are equal in length.

Between said four-point resistance measurement circuit and said CS1180 analog-to-digital converter, a multiplexer and an amplifying filter circuit connected in sequence are provided; said amplifying and filtering circuit comprises resistors R1, R2, R3, R4 and amplifier AD620 The first-stage amplifying circuit constituted is a second-order RC low-pass filter composed of resistor R5 and capacitor C1, resistor R7 and capacitor C2.

The working principle of the data collector 17 provided by the present invention: the surface of the humidity detection area is covered with a layer of filter screen 19, which filters other impurity particles in the surrounding environment except moisture, and only absorbs moisture in the air. The quality of the π-type giant piezoresistive structure 5 changes and generates stress, and the stress is enhanced by the stress-enhancing structure, and the enhanced stress further leads to greater stress on the surface of the π-type giant piezoresistive structure 5, especially in the root region, which leads to π The silicon-germanium heterojunction 12 and the gold-silicon-germanium heterojunction 13 of the type giant piezoresistive structure 5 produce a giant piezoresistive effect, that is, the stress after the enhancement adjusts the silicon-germanium heterojunction 12 and the gold-silicon-germanium heterojunction 12 The height of the potential barrier of the heterojunction 13 greatly changes the number of electrons passing through, so that the resistance undergoes an order of magnitude change. Compared with traditional humidity sensors that detect humidity changes through resistance and capacitance changes, this humidity sensor first converts humidity changes into stress changes, and then enhances the stress and adopts a π-type that can produce more obvious resistance changes under the same stress conditions. The giant piezoresistive structure, so that the invention significantly improves the sensitivity of the humidity sensor from the sensing structure and widens its measuring range.

Example

The strain sensitivity coefficient of the traditional bulk silicon piezoresistive structure is generally between 50-100, and is easily affected by the ambient temperature. In order to illustrate the technical effect of the humidity sensor provided by the present invention, the strain sensitivity coefficient of the π-type giant piezoresistive structure proposed by the present invention is measured in the temperature range of -20-60 degrees by using a four-point bending test device, and the test results show that: π The strain sensitivity coefficient of the large piezoresistive structure can reach more than 1000. At the same time, the influence of the size change of the silicon-germanium heterojunction and the gold-silicon-germanium heterojunction on the strain sensitivity coefficient is investigated. When the silicon-germanium heterojunction When the length is 5 μm, the strain sensitivity coefficient changes greatly in magnitude and can reach 3000. In addition, the influence of temperature on the strain sensitivity of the π-type giant piezoresistive structure is also significant, and the temperature drift error reaches 3%FS-5%FS.

Due to the complex environment in which the humidity is measured, the ambient temperature is not constant, and the humidity sensor is made of semiconductor materials, so it is very susceptible to the influence of temperature. Considering that the ambient temperature will bring considerable errors to the humidity measurement of the sensor, the present invention provides a method for correcting temperature drift of the humidity sensor based on the π-type giant piezoresistive structure. The method is as follows: STM32F407 single-chip The fitting function H _standard =f(V, T) performs real-time compensation and correction on the influence of temperature drift, and the method for obtaining the quadratic surface fitting function H _standard =f(V, T) includes the following steps:

Step 1, put the humidity sensor into the constant temperature and humidity test chamber, determine the humidity when the temperature T = 20 degrees as the standard humidity H _standard , and then adjust the temperature in the test chamber, the adjustment range is -20-60 degrees, and the step size is 10 degrees, get the output voltage value V(T) of the humidity sensor at different temperatures;

Step 2, change the standard humidity H _standard , repeat step 1, obtain the output voltage value V (H _standard , T) of the humidity sensor under different temperatures and different humidity, and use the output voltage value V and temperature value T of the humidity sensor as the to-be-built The input variable of the standard humidity surface equation H _standard = (V, T), so the influence of the temperature factor can be taken into account when analyzing the humidity;

Step 3, as shown in Figure 6, use the discrete data for constructing the H _standard =(V, T) surface equation measured by the above experiment to carry out quadratic surface fitting, and adopt the least squares method to determine the quadratic surface fitting function H _standard = the coefficients of the independent variables V and T in f(V, T), so as to determine the quadratic surface fitting function H _standard = f(V, T). Using the least squares method to determine the coefficients of the quadratic surface fitting function can minimize the error between the humidity value calculated using the quadratic surface fitting function _Hstandard =f(V, T) and the _standard humidity value Hstandard.

The quadratic surface fitting function H _standard = f (V, T) is the surface fitting mathematical prediction model between the measured humidity of the sensor, the ambient temperature and the output voltage, and can be conveniently obtained after the sensor output voltage and the ambient temperature Calculate the measured humidity value accurately. The quadratic surface fitting function _Hstandard =f(V,T) includes the temperature T, and the influence of temperature drift is removed by establishing a nonlinear mapping relationship between temperature and humidity to realize temperature compensation. Transplanting the quadratic surface fitting function to the STM32 microcontroller can perform real-time temperature drift compensation correction.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. It should also be regarded as the protection scope of the present invention.

Claims (10)

1. Based on the humidity sensor of π type giant piezoresistive structure, it is characterized in that: comprise 4 data collectors, data conversion integrated layer and filter screen, 4 described data collectors are divided into two rows and are distributed on the data conversion integrated layer, The filter screen is placed on the detection area of the data collector, and the data conversion integrated layer includes a four-point resistance measurement circuit, a CS1180 analog-to-digital converter, a STM32F407 single-chip microcomputer and a TFT true-color liquid crystal display; 4 data collectors The collected data is transmitted to the CS1180 analog-to-digital converter through the four-point resistance measurement circuit. After conversion, the CS1180 analog-to-digital converter is output to the STM32F407 single-chip microcomputer, and the STM32F407 single-chip microcomputer sends it to the TFT true-color LCD display. On the TFT true-color LCD display on display; The data collector includes a substrate, a stress layer, a detection area and a π-type giant piezoresistive structure, the stress layer is placed on the substrate, and the detection area and the π-type giant piezoresistive structure are distributed on the stress layer , wherein the detection area is placed in the center of the stress layer, there are two π-type giant piezoresistive structures, distributed on both sides of the detection area and at the edge of the stress layer, and the two π-type giant piezoresistive structures The piezoresistive structure is connected in series through a connecting line made of metal aluminum, and powered by a constant current source; the π-type giant piezoresistive structure includes a silicon structure area, a germanium structure area and a gold structure area, wherein the silicon structure area is divided into two sections, divided into Arranged at both ends of the germanium structure region, the gold structure region is placed on the same side of the silicon structure region and the germanium structure region, and the length of the gold structure region is equal to the length of the two silicon structure regions and the germanium structure region The sum of the lengths, the junction of the silicon structure region and the germanium structure region is a silicon-germanium heterojunction, and the junction of the gold structure region and the silicon structure region and germanium structure region is gold-silicon-germanium Heterojunction; the other side of the germanium structure region is provided with a potential monitoring point; one side of the π-type giant piezoresistive structure is provided with a temperature sensor for real-time detection of ambient temperature. 2. The humidity sensor based on the π-type giant piezoresistive structure according to claim 1, characterized in that: a solid support structure of monocrystalline silicon is provided between the stress layer and the substrate to prevent the stress layer from Rupture due to excessive pressure. 3. The humidity sensor based on the π-type giant piezoresistive structure according to claim 2, characterized in that: a heating device is provided between the stress layer and the solid support structure, and the heating device is a polysilicon resistance wire. 4. The humidity sensor based on the π-type giant piezoresistive structure according to claim 1, characterized in that: the data collector also includes two common-mode signal signals of the same size and composition materials as the π-type giant piezoresistive structure A compensation structure, the two common-mode signal compensation structures are located at both ends of the detection area and at the edge of the stress layer, forming a square structure with the two π-type giant piezoresistive structures, and the common-mode signal compensation The structure is connected in series with the π-type giant piezoresistive structure through a connecting line made of metal aluminum, and powered by the same constant current source. 5. The humidity sensor based on the π-type giant piezoresistive structure according to claim 1, characterized in that: the surrounding of the π-type giant piezoresistive structure is provided with a U-shaped stress enhancement structure; the stress enhancement structure adopts RIE Etching technology etches groove-like structures on the stress layer. 6. The humidity sensor based on the π-type giant piezoresistive structure according to claim 1, characterized in that: the material of the substrate is glass, the material of the stress layer is silicon dioxide, and the material of the detection area is polyimide . 7. The humidity sensor based on the π-type giant piezoresistive structure according to claim 1, characterized in that: between the four-point resistance measurement circuit and the CS1180 analog-to-digital converter, there are sequentially connected multiplexers amplifier and amplifying and filtering circuit; the amplifying and filtering circuit includes a first-stage amplifying circuit composed of resistors R1, R2, R3, R4 and amplifier AD620, and a second-order RC low composed of resistor R5 and capacitor C1, resistor R7 and capacitor C2 pass filter. 8. The humidity sensor based on the π-type giant piezoresistive structure according to claim 1, characterized in that: the size of the silicon-germanium heterojunction is (60-70) μm*5 μm*(50-150) nm , the size of the gold-silicon-germanium heterojunction is (60-70) μm*(35-50) μm*(50-150) nm. 9. The humidity sensor based on the π-type giant piezoresistive structure according to claim 1, characterized in that: a titanium structure area is provided between the gold structure area, the silicon structure area, and the germanium structure area for fixing The gold structure region, the length of the titanium structure region is equal to the length of the gold structure region. 10. The temperature drift correction method based on the humidity sensor of π-type giant piezoresistive structure according to any one of claims 1-9, characterized in that: STM32F407 single-chip microcomputer utilizes quadratic surface fitting function H _standard =f(V, T) real-time compensation correction is carried out to the influence of temperature drift, and the obtaining method of described quadratic surface fitting function H _standard =f (V, T) comprises the following steps: Step 1, put the humidity sensor into the constant temperature and humidity test chamber, determine the humidity when the temperature T = 20 degrees as the standard humidity H _standard , and then adjust the temperature in the test chamber, the adjustment range is -20-60 degrees, and the step size is 10 degrees, get the output voltage value V(T) of the humidity sensor at different temperatures; Step 2, change the standard humidity H _standard , repeat step 1, obtain the output voltage value V (H _standard , T) of the humidity sensor under different temperatures and different humidity, and use the output voltage value V and temperature value T of the humidity sensor as the to-be-built The input variable of the standard humidity surface equation H _standard = (V, T), so the influence of the temperature factor can be taken into account when analyzing the humidity; Step 3, use the discrete data for constructing the surface equation H _standard =(V, T) of above-mentioned experimental measurement to carry out quadratic surface fitting, and adopt least squares method to determine quadratic surface fitting function H _standard =f(V , T) in the coefficients of the independent variables V and T, so as to determine the quadratic surface fitting function H _standard = f (V, T).