Piezoresistive pressure sensor passive resistance network temperature compensation method

Abstract

The invention relates to the field of signal conditioning of piezoresistive pressure sensors and provides a passive resistance network temperature compensation method for a piezoresistive pressure sensor in order to solve the problem that in a high-temperature test environment, the bridge output zero position and the sensitivity voltage of a sensitive chip of the pressure sensor drift along with the change of the test temperature, and the measurement precision is affected. A low-temperature-coefficient resistance network compensation model is adopted, a corresponding compensation model is selected according to positive and negative normal-temperature initial zero voltage of the piezoresistive pressure sensor, and bridge zero temperature drift compensation and bridge sensitivity temperature drift compensation are achieved through the compensation model. According to the piezoresistive pressure sensor, the output voltage of the piezoresistive pressure sensor does not change along with the temperature under the loading of the initial pressure, and the output voltage of the piezoresistive pressure sensor does not change along with the temperature under the loading of the variable pressure. Influences such as residual stress of piezoresistive pressure sensor packaging and parameter offset of a bridge itself are overcome, and high-precision temperature compensation is realized.

Description

Technical Field

[0001] The present invention relates to the field of piezoresistive pressure sensor signal conditioning, and more specifically, to a piezoresistive pressure sensor passive resistor network temperature compensation method. Background Art

[0002] In recent years, with the progress of science such as vehicles, petrochemicals, aerospace and military, the application demand for pressure sensors in high temperature environments has greatly increased. In the industrial field and the aerospace and military fields, high temperature resistant pressure sensors are widely used to obtain pressure information, and their working performance directly affects the measurement of signals. For example, in the measurement of oil pressure in oil exploration and production, the pressure sensor needs to work in a high temperature environment of 220°C; in the field of automotive electronics, the pressure sensor is used for the pressure measurement of the engine throttle, and its working temperature can reach 350°C; in the pressure vessel and pipeline pressure detection application in metallurgical and chemical production, the pressure sensor needs to operate at a working temperature of up to 480°C. It can be seen that the influence of temperature on the sensor is a factor that must be considered when measuring pressure.

[0003] Commonly used temperature compensation methods include hardware compensation and software compensation. Among them, there are many ways of hardware compensation, and the commonly used hardware compensation methods include thermistor compensation, low temperature coefficient resistor network compensation, diode compensation, transistor compensation and gain-adjustable operational amplifier compensation; software compensation methods usually use model algorithms such as difference algorithms and neural networks. Compared with software compensation, hardware compensation is simple, efficient and low-cost, and is easier to implement in industrial production and manufacturing, so it is widely used. Compared with other hardware compensation methods, the biggest advantage of the low temperature coefficient resistor network compensation method is that it does not require the compensation circuit to be close to the bridge arm resistor of the sensitive head, which makes the low temperature coefficient resistor network compensation circuit more flexible to use and the sensor sensitive head packaging more convenient. At the same time, the compensation accuracy is greatly improved because the influence of the ambient temperature gradient between the compensation circuit and the piezoresistive bridge is eliminated. However, the premise of the traditional passive resistor network temperature compensation method is that the resistance values ​​of the four bridge arm resistors of the piezoresistive bridge are not much different, the temperature coefficient is consistent, and the influence of residual stress after sensor packaging is not considered, otherwise the zero temperature drift compensation will fail, thereby affecting the sensitivity temperature compensation effect.

[0004] However, in a high-temperature test environment, due to the characteristics of semiconductor materials themselves, the piezoresistors of the sensitive chip of a silicon-based MEMS piezoresistive pressure sensor have a positive temperature coefficient, and the resistance value of the piezoresistors will increase with the increase of the test temperature; while the chip itself has a piezoresistive coefficient with a negative temperature coefficient, which decreases with the increase of the test temperature. The result is that both the zero position of the bridge output and the sensitivity voltage of the sensitive chip of the pressure sensor will drift with the change of the test temperature. Therefore, temperature drift is the main factor affecting its measurement accuracy, and a method capable of achieving high-precision temperature compensation is urgently needed. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a passive resistor network temperature compensation method for a piezoresistive pressure sensor. Based on the actual measurement data after the piezoresistive pressure sensor is packaged, this invention overcomes the influences of the residual stress of the piezoresistive pressure sensor package, the offset of the bridge's own parameters, etc., and realizes high-precision temperature compensation.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A passive resistor network temperature compensation method for a piezoresistive pressure sensor adopts a low-temperature coefficient resistor network compensation model, and selects the corresponding compensation model according to the positive or negative of the initial zero voltage at room temperature of the piezoresistive pressure sensor. The compensation model is used to realize the zero-position temperature drift compensation of the bridge and the sensitivity temperature drift compensation of the bridge, so that the output voltage of the piezoresistive pressure sensor does not change with temperature under the initial pressure P0 load, and the output voltage of the piezoresistive pressure sensor does not change with temperature under the changing pressure P1 load, completing the temperature compensation. The specific steps are as follows:

[0008] Step 1. Test the piezoresistive pressure sensor to obtain the resistance values of the four bridge arms of the bridge circuit of the sensor at two compensation temperature thresholds T0 and T1, where T0 < T1, and two pressure loads P0 and P1, where P0 < P1.

[0009] Step 2. Substitute the resistance values obtained in Step 1 into the following formula to calculate the compensation resistance value:

[0010]

[0011] where, V OUT (T0, P0) is the output voltage of the piezoresistive pressure sensor at temperature T0 and pressure P0; V OUT (T1, P0) is the output voltage of the piezoresistive pressure sensor at temperature T1 and pressure P0; V OUT (T0, P1) is the output voltage of the piezoresistive pressure sensor at temperature T0 and pressure P1, V OUT(T1, P1) is the output voltage of the piezoresistive pressure sensor at temperature T1 and pressure P1, and U0 is the zero-position voltage of the piezoresistive pressure sensor;

[0012] Step 3. Connect the resistor corresponding to the compensation resistor value obtained in step 2 to the circuit to complete temperature compensation.

[0013] Furthermore, the compensation model includes a compensation model 1 in which the initial zero-position voltage of the piezoresistive pressure sensor at room temperature is negative and a compensation model 2 in which the initial zero-position voltage of the piezoresistive pressure sensor at room temperature is positive. Both compensation models include an input terminal Vin and an output terminal V OUT , and the bridge circuit structure, the piezoresistive pressure sensor output voltage:

[0014] V OUT (T,P)=V B (T,P)×[K + (T,P)-K - (T, P)]

[0015] Among them, K + (T,P) is the voltage divider coefficient of the positive end of the bridge output, K - (T,P) is the voltage divider coefficient of the negative end of the bridge output, V B (T,P) is the bridge supply voltage, V OUT (T, P) is the bridge output voltage, i.e., the output voltage of the piezoresistive pressure sensor, T is the temperature, and P is the pressure;

[0016] The bridge supply voltage is V B (T,P):

[0017]

[0018] Among them, V IN is the bridge input voltage, R B (T,P) represents the total resistance of the bridge when the temperature is T and the pressure is P, and Rs is the bridge compensation resistance.

[0019] Furthermore, the first bridge arm of the bridge circuit of compensation model one is a resistor R11 and a resistor Rp1 connected in parallel, the second bridge arm and the third bridge arm are resistors R12 and R13 respectively, the fourth bridge arm is a resistor R14 and a resistor Rz1 connected in series, the positive electrode of the input end is connected between the first bridge arm and the second bridge arm through the resistor Rs1, the negative electrode of the input end is connected between the third bridge arm and the fourth bridge arm, the positive electrode of the output end is connected between the first bridge arm and the fourth bridge arm, and the negative electrode of the output end is connected between the second bridge arm and the third bridge arm.

[0020] Furthermore, the output voltage of compensation model 1 is:

[0021]

[0022] Among them, R1i(T,P) (i = 1, 2, 3, 4) is the bridge varistor of compensation model one, and Rz1, Rp1, Rs1 are the parameter values of compensation model one to be solved.

[0023] Furthermore, the first arm of the bridge circuit of compensation model two is composed of resistor R21 and resistor Rz2 in series, the second arm and the third arm are resistor R22 and resistor R23 respectively, the fourth arm is resistor R24 and resistor Rp2 in parallel, the positive pole of the input end is connected between the first arm and the second arm through resistor Rs2, the negative pole of the input end is connected between the third arm and the fourth arm, the positive pole of the output end is connected between the first arm and the fourth arm, and the negative pole of the output end is connected between the second arm and the third arm.

[0024] Furthermore, the output voltage of the bridge circuit of compensation model two is:

[0025]

[0026] Among them, R2i(T,P) (i = 1, 2, 3, 4) is the bridge varistor of compensation model two, and Rz2, Rp2, Rs2 are the parameter values of compensation model two to be solved.

[0027] In summary, the invention has the following beneficial effects:

[0028] The present invention performs temperature compensation according to the actual measurement data after the piezoresistive pressure sensor is encapsulated. Compared with the traditional low-temperature coefficient resistor network compensation method, the present invention is not affected by the residual stress of the piezoresistive pressure sensor encapsulation, the parameter offset of the bridge itself, etc. The compensation model of the present invention is simple, and only four arm resistance values under two compensation temperature thresholds T0, T1 (T0 < T1) and two pressure loads P0, P1 (P0 < P1) of the piezoresistive pressure sensor need to be provided. The compensation resistance value is obtained according to the arm resistance value and the compensation resistance is connected into the compensation model, with high compensation accuracy and wide application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the circuit schematic diagram of the compensation model when the initial zero voltage of the sensor at room temperature is negative;

[0030] Figure 2 It is the circuit schematic diagram of the compensation model when the initial zero voltage of the sensor at room temperature is positive;

[0031] Figure 3 It is the output curve diagram of the sensor by the traditional compensation method;

[0032] Figure 4 It is the output curve diagram of the sensor by this method. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings.

[0034] It should be noted that for the sake of convenience of expression, the description of directions in the following text is consistent with the directions of the accompanying drawings themselves, but it does not limit the structure of the present invention.

[0035] As Figures 1 to 4 shown, the present invention discloses a passive resistor network temperature compensation method for a piezoresistive pressure sensor. Based on the actual measurement data after the piezoresistive pressure sensor is encapsulated, it overcomes the influences of the residual stress of the piezoresistive pressure sensor encapsulation, the offset of the parameters of the bridge itself, etc., realizes high-precision temperature compensation, adopts a low temperature coefficient resistor network compensation model, and selects the corresponding compensation model according to the positive or negative of the initial zero voltage at room temperature of the piezoresistive pressure sensor. The compensation model is used to realize the zero-bit temperature drift compensation of the bridge and the sensitivity temperature drift compensation of the bridge, so that the output voltage of the piezoresistive pressure sensor does not change with temperature under the initial pressure P0 load, and the output voltage of the piezoresistive pressure sensor does not change with temperature under the changing pressure P1 load, and the temperature compensation is completed. The specific steps are as follows:

[0036] Step 1. Test the piezoresistive pressure sensor to obtain the resistance values of the four bridge arms of the bridge circuit of the sensor at two compensation temperature thresholds T0 and T1, where T0 < T1, and two pressure loads P0 and P1, where P0 < P1. The compensation model includes compensation model one with a negative initial zero voltage at room temperature of the piezoresistive pressure sensor and compensation model two with a positive initial zero voltage at room temperature of the piezoresistive pressure sensor. Both compensation models include an input terminal Vin and an output terminal V OUT , and the bridge circuit structure, and the output voltage of the piezoresistive pressure sensor:

[0037] V OUT (T, P) = V B (T, P) × [K + (T, P) - K - (T, P)] (1)

[0038] Wherein, K + (T, P) is the positive terminal voltage division coefficient of the bridge output, K - (T, P) is the negative terminal voltage division coefficient of the bridge output, V B (T, P) is the bridge supply voltage, V OUT (T, P) is the bridge output voltage, that is, the output voltage of the piezoresistive pressure sensor, T is the temperature, and P is the pressure; the parameters in the brackets after the present invention represent the parameters under the conditions of temperature T and pressure P. When the temperature T and / or the pressure P change, the circuit parameters will also change.

[0039] The supply voltage of the bridge is V B(T,P):

[0040]

[0041] Among them, V IN is the bridge input voltage, R B (T, P) represents the total resistance of the bridge when the temperature is T and the pressure is P, Rs is the compensation resistance of the bridge, and the compensation resistance of the two compensation models are calculated using the above formula.

[0042] The first bridge arm of the bridge circuit of compensation model 1 is a resistor R11 and a resistor Rp1 connected in parallel, the second bridge arm and the third bridge arm are resistors R12 and R13 respectively, the fourth bridge arm is a resistor R14 and a resistor Rz1 connected in series, the positive electrode of the input end is connected between the first bridge arm and the second bridge arm through resistor Rs1, the negative electrode of the input end is connected between the third bridge arm and the fourth bridge arm, the positive electrode of the output end is connected between the first bridge arm and the fourth bridge arm, and the negative electrode of the output end is connected between the second bridge arm and the third bridge arm. Output voltage of compensation model 1:

[0043]

[0044] Among them, R1i(T,P)(i=1,2,3,4) is the bridge varistor of compensation model one, and Rz1, Rp1, Rs1 are the parameter values ​​of compensation model one to be solved.

[0045] The first bridge arm of the bridge circuit of compensation model 2 is a series connection of resistors R21 and Rz2, the second bridge arm and the third bridge arm are resistors R22 and R23 respectively, the fourth bridge arm is a parallel connection of resistors R24 and Rp2, the positive electrode of the input end is connected between the first bridge arm and the second bridge arm through resistor Rs2, the negative electrode of the input end is connected between the third bridge arm and the fourth bridge arm, the positive electrode of the output end is connected between the first bridge arm and the fourth bridge arm, and the negative electrode of the output end is connected between the second bridge arm and the third bridge arm. The output voltage of the bridge circuit of compensation model 2 is:

[0046]

[0047] Among them, R2i(T,P)(i=1,2,3,4) is the bridge varistor of compensation model 2, and Rz2, Rp2, Rs2 are the parameter values ​​of compensation model 2 to be solved.

[0048] For compensation model 1, the bridge resistance is:

[0049] R B (T,P)=[R2(T,P)+R3(T,P)]||||[R Z +R4(T,P)+R1(T,P)|||R P ] (5)

[0050] Voltage division coefficient:

[0051]

[0052] Substituting formulas (2), (5) - (7) into formula (1) can obtain formula (3). Similarly, the output voltage expression of compensation model two, namely formula (4), can be obtained.

[0053] Step 2. Substitute the resistance values obtained in Step 1 into the following formula to calculate the compensation resistance value:

[0054]

[0055] Among them, V OUT (T0, P0) is the output voltage of the piezoresistive pressure sensor at temperature T0 and pressure P0; V OUT (T1, P0) is the output voltage of the piezoresistive pressure sensor at temperature T1 and pressure P0; V OUT (T0, P1) is the output voltage of the piezoresistive pressure sensor at temperature T0 and pressure P1, V OUT (T1, P1) is the output voltage of the piezoresistive pressure sensor at temperature T1 and pressure P1, and U0 is the zero - voltage of the piezoresistive pressure sensor. According to the requirements of bridge compensation, the passive resistance network temperature compensation model, namely formula (9), is联立 as follows:

[0056]

[0057] The bridge zero - point temperature drift compensation requires that the output voltage of the sensor does not change with temperature under the initial pressure P0 load, that is, the partial derivative of V OUT (T, P0) with respect to temperature is zero; the bridge sensitivity temperature drift compensation requires that the output voltage of the sensor does not change with temperature under a higher pressure P1 load, that is, the partial derivative of V OUT (T, P1) with respect to temperature is zero.

[0058] The output signal V OUT (T, P) of the pressure - sensitive chip unit has a linear relationship with temperature and pressure. V OUT (T, P) can be simplified to a first - order function of variables T and P. Simplifying formula (9) can obtain formula (8). According to the test results of different sensors, different compensation schemes are selected to calculate the compensation model parameters. The measurement parameters that need to be provided only include the four arm - resistance values of the high - temperature pressure sensor at two compensation temperature thresholds T0, T1 (T0 < T1) and two pressure loads P0, P1 (P0 < P1), as shown in Table 1:

[0059] Table 1 Sensor measurement parameters required for the compensation model

[0060] R1 R2 R3 R4 (T0, P0) R1(T0, P0) R2(T0, P0) R3(T0, P0) R4(T0,P0) (T0, P1) R1(T0, P1) R2(T0,P1) R3(T0, P1) R4(T0,P1) (T1, P0) R1(T1,P0) R2(T1,P0) R3(T1,P0) R4(T1,P0) (T1, P1) R1(T1, P1) R2(T1, P1) R3(T1,P1) R4(T1,P1)

[0061] Step 3. Connect the resistor corresponding to the compensation resistor value obtained in step 2 to the circuit to complete temperature compensation.

[0062] like Figure 3 The figure shows the output curve of the sensor using the traditional compensation method. The horizontal axis is the pressure P, and the vertical axis is the sensor output voltage. The black, red, and blue lines represent the sensor output characteristic curves when T=25, 100, and 235℃, respectively.

[0063] From the shown Figure 3 It can be observed that the maximum thermal zero drift of the sensor reaches 0.1018% FS / ℃, while the maximum thermal sensitivity drift is 0.1035% FS / ℃. Obviously, this conventional compensation method does not achieve the ideal compensation effect.

[0064] like Figure 4 As shown in the figure, the sensor output curve using this compensation method. The horizontal axis is the pressure P, and the vertical axis is the sensor output voltage. The black, red, and blue lines represent the sensor output characteristic curves when T=25, 100, and 235℃ respectively.

[0065] From the shown Figure 4 It can be observed that the maximum thermal zero drift of the sensor is only 0.0781%FS / ℃, and the maximum thermal sensitivity drift is only 0.0717%FS / ℃. Compared with the traditional passive resistor network temperature compensation method, the passive resistor network temperature compensation method shows a better temperature compensation effect, and the sensor temperature drift is reduced by an order of magnitude.

[0066] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A temperature compensation method for a passive resistor network of a piezoresistive pressure sensor, characterized in that: Adopt a low temperature coefficient resistance network compensation model, and select the corresponding compensation model according to the positive or negative of the initial zero position voltage of the piezoresistive pressure sensor at room temperature. Use the compensation model to achieve zero position temperature drift compensation and sensitivity temperature drift compensation of the bridge, so that the output voltage of the piezoresistive pressure sensor does not change with temperature under the initial pressure P0 load, and the output voltage of the piezoresistive pressure sensor does not change with temperature under the changing pressure P1 load, and complete the temperature compensation. The specific steps are as follows: Step 1. Test the piezoresistive pressure sensor to obtain the resistance values of the four bridge arms of the bridge circuit of the sensor at two compensation temperature thresholds T0 and T1, where T0 < T1, and two pressure loads P0 and P1, where P0 < P1. Step 2. Substitute the resistance values obtained in Step 1 into the following formula to calculate the compensation resistance value: Among them, V OUT (T0, P0) is the output voltage of the piezoresistive pressure sensor at temperature T0 and pressure P0; V OUT (T1, P0) is the output voltage of the piezoresistive pressure sensor at temperature T1 and pressure P0; V OUT (T0, P1) is the output voltage of the piezoresistive pressure sensor at temperature T0 and pressure P1, V OUT (T1, P1) is the output voltage of the piezoresistive pressure sensor at temperature T1 and pressure P1, and U0 is the zero-position voltage of the piezoresistive pressure sensor; Step 3. Connect the resistor corresponding to the compensation resistance value obtained in Step 2 to the circuit to complete the temperature compensation.

2. The method for temperature compensation of a passive resistor network of a piezoresistive pressure sensor according to claim 1, characterized in that: The compensation model includes a compensation model 1 in which the initial zero-position voltage of the piezoresistive pressure sensor at room temperature is negative and a compensation model 2 in which the initial zero-position voltage of the piezoresistive pressure sensor at room temperature is positive. Both compensation models include an input terminal Vin and an output terminal V OUT , and the bridge circuit structure, the piezoresistive pressure sensor output voltage: V OUT (T,P)=V B (T,P)×[K + (T,P)-K(T,P)] Among them, K + (T,P) is the voltage divider coefficient of the positive end of the bridge output, K - (T,P) is the voltage divider coefficient of the negative end of the bridge output, V B (T,P) is the bridge supply voltage, V OUT (T, P) is the bridge output voltage, i.e., the output voltage of the piezoresistive pressure sensor, T is the temperature, and P is the pressure; The bridge supply voltage is V B (T,P): Among them, V IN is the bridge input voltage, R B (T,P) represents the total resistance of the bridge when the temperature is T and the pressure is P, and Rs is the bridge compensation resistance.

3. The method for temperature compensation of a passive resistor network of a piezoresistive pressure sensor according to claim 2, characterized in that: The first bridge arm of the bridge circuit of the compensation model one is the parallel connection of resistor R11 and resistor Rp1, the second and third bridge arms are resistor R12 and resistor R13 respectively, and the fourth bridge arm is the series connection of resistor R14 and resistor Rz1. The positive pole of the input terminal is connected between the first and second bridge arms through resistor Rs1, the negative pole of the input terminal is connected between the third and fourth bridge arms, the positive pole of the output terminal is connected between the first and fourth bridge arms, and the negative pole of the output terminal is connected between the second and third bridge arms.

4. The method for temperature compensation of a passive resistor network of a piezoresistive pressure sensor according to claim 3, characterized in that: The output voltage of the compensation model one: Among them, R1i(T,P) (i = 1, 2, 3, 4) is the piezoresistive resistor of the bridge of the compensation model one, and Rz1, Rp1, Rs1 are the parameter values of the compensation model one to be solved.

5. The method for temperature compensation of a passive resistor network of a piezoresistive pressure sensor according to claim 2, characterized in that: The first bridge arm of the bridge circuit of the compensation model two is the series connection of resistor R21 and resistor Rz2, the second and third bridge arms are resistor R22 and resistor R23 respectively, and the fourth bridge arm is the parallel connection of resistor R24 and resistor Rp2. The positive pole of the input terminal is connected between the first and second bridge arms through resistor Rs2, the negative pole of the input terminal is connected between the third and fourth bridge arms, the positive pole of the output terminal is connected between the first and fourth bridge arms, and the negative pole of the output terminal is connected between the second and third bridge arms.

6. The method for temperature compensation of a passive resistor network of a piezoresistive pressure sensor according to claim 5, characterized in that: The output voltage of the bridge circuit of the compensation model two is: Among them, R2i(T,P) (i = 1, 2, 3, 4) is the piezoresistive resistor of the bridge of the compensation model two, and Rz2, Rp2, Rs2 are the parameter values of the compensation model two to be solved.

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