CN106441644A - Silicon piezoresistive pressure sensor temperature drift compensation method - Google Patents

Abstract

The invention relates to a silicon piezoresistive pressure sensor temperature drift compensation method. The pressure output value UT' after temperature compensation under a certain temperature T DEG C is a<0>+(U<r>-a<r>/b<r>)xb(0) through linear compensation of the zero position and the sensitivity of a pressure sensor line. The beneficial effects are that the error of a silicon piezoresistive pressure sensor caused by the change of temperature can be effectively avoided, and nonlinear correction, zero position temperature compensation and sensitivity temperature compensation can be performed on the pressure sensor.

Description

Method for compensating temperature drift of silicon piezoresistive pressure sensor

Technical Field

The invention relates to the related technical field of circuit design applied to signal conditioning of a silicon piezoresistive pressure sensor, in particular to a compensation method for temperature drift of the pressure sensor.

Background

The silicon piezoresistive pressure sensor measures the pressure value of an object by using the wheatstone bridge principle, and generally, four equal resistors are diffused on a circular silicon film and are connected into a wheatstone bridge, as shown in fig. 1.

Due to the characteristics of silicon materials, the pressure response characteristics of silicon piezoresistive pressure sensors at different temperatures are not uniform. In order to avoid the influence of temperature on the pressure sensor, the linear characteristics of the pressure sensor at different temperature points are improved, and the pressure sensor needs to be correspondingly temperature-compensated.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a compensation method for temperature drift of a silicon piezoresistive pressure sensor, which is realized by the following specific technical scheme:

the compensation method for the temperature drift of the silicon piezoresistive pressure sensor comprises the following steps:

1) in the temperature interval [ T₁，T₂]Inner, T₁、T₂Are all temperature values, and T₁<T₂Selecting a plurality of temperature points T, keeping the temperature T unchanged, collecting pressure output values under different pressures P, calculating a first-order linear formula of the pressure output values by a linear fitting method, and calculating second-order fitting formulas a (T) and b (T) of the temperature points by performing second-order linear fitting on the zero point a and the sensitivity b of the temperature points according to the first-order linear formula to obtain the zero points a (T) corresponding to the different temperature points T_TAnd sensitivity b_T；

2) In the temperature interval [ T₁，T₂]Setting a known selected fitting temperature point T, and judging the fitting temperature interval [ T ] in which the temperature point T is positioned₃，T₄]，T₁、T₂、T₃、T₄Are all temperature values, and T₁＜T₃≤T≤T₄＜T₂By the linear difference formulaCalculating the pressure output value U of the temperature point T_TWherein U is₃、U₄Respectively is a temperature point T₃、T₄A lower pressure output value;

3) calculating a compensated pressure output value U 'according to the formula (2)'_TIn the formula (2), a₀Zero position of the sensor at ambient temperature, b₀Is the sensitivity of the sensor at normal temperature

The method for compensating the temperature drift of the silicon piezoresistive pressure sensor is further designed in the following way, the first-order linear formula in the step 1) is shown as the formula (1), and a in the formula (1)_T、b_TRespectively the zero position and the sensitivity of the sensor at a certain temperature T ℃, and P is the measured pressure value of the sensor; u shape_TFor sensor pressure output value

U_T＝a_T+b_T×P(1)。

The method for compensating the temperature drift of the silicon piezoresistive pressure sensor is further designed in the step 1)

a(T)＝a₀+α(T-T₀)*Y(FS)

b(T)＝b₀+β(T-T₀)*Y(FS) (3)

Wherein alpha is a zero temperature coefficient; beta is the sensitivity temperature coefficient, and Y (FS) is the full scale output value.

The invention has the following advantages:

the compensation method for the temperature drift of the silicon piezoresistive pressure sensor can be applied to the signal conditioning circuit design of the silicon piezoresistive pressure sensor, and the output stability of the silicon piezoresistive pressure sensor is improved.

Drawings

FIG. 1 is a schematic block diagram of a method of compensating for temperature drift in a silicon piezoresistive pressure sensor in accordance with the present invention.

FIG. 2 is a schematic diagram of a Wheatstone bridge of a silicon piezoresistive pressure sensor.

Detailed Description

The following describes the present invention in detail with reference to the accompanying drawings.

The method for compensating the temperature drift of the silicon piezoresistive pressure sensor comprises the following steps:

1) in the temperature interval [ T₁，T₂]Inner, T₁、T₂Are all temperature values, and T₁＜T₂Selecting a plurality of temperature points T, keeping the temperature T unchanged, collecting pressure output values under different pressures P, calculating a first-order linear formula of the pressure output values by a linear fitting method, performing second-order linear fitting on the zero point a and the sensitivity b of each temperature point according to the first-order linear formula, calculating second-order fitting formulas a (T) and b (T) of each temperature point, and obtaining the zero points a (T) corresponding to different temperature points T according to the second-order fitting formulas a (T) and b (T)_TAnd sensitivity b_T；

2) In the temperature interval [ T₁，T₂]Setting a known selected fitting temperature point T, and judging the fitting temperature interval [ T ] in which the temperature point T is positioned₃，T₄]，T₁、T₂、T₃、T₄Are all temperature values, and T₁＜T₃≤T≤T₄＜T₂By the linear difference formulaCalculating the pressure output value U of the temperature point T_TWherein U is₃、U₄Respectively is a temperature point T₃、T₄A lower pressure output value;

3) calculating a compensated pressure output value U 'according to the formula (2)'_TIn the formula (2), a₀Zero position of the sensor at ambient temperature, b₀Is the sensitivity of the sensor at normal temperature

The first-order linear formula in the step 1) is shown as the formula (1), wherein a in the formula (1)_T、b_TRespectively the zero position and the sensitivity of the sensor at a certain temperature T ℃, and P is the measured pressure value of the sensor; u shape_TFor sensor pressure output value

U_T＝a_T+b_T×P(1)。

The output of the pressure sensor at room temperature from equation 1 is:

U₀＝a₀+b₀×P (4)

wherein,

a(T)＝a₀+α(T-T₀)*Y(FS)

b(T)＝b₀+β(T-T₀)*Y(FS) (3)

wherein alpha is a zero temperature coefficient; beta is the sensitivity temperature coefficient, and Y (FS) is the full scale output value.

From the formulae (1), (2), (3) and (4), a temperature-compensated pressure output value U 'can be obtained'_TComprises the following steps:

the response of the silicon piezoresistive pressure sensor varies with temperature, as shown in table 1. The measuring range of the sensor is 0-35 kPa (gauge pressure), the compensation temperature is 0-50 ℃, and the excitation power supply is 1 mA.

TABLE 1 pressure output of silicon pressure sensor as a function of temperature

Keeping the temperature T constant, for the pressure P and the output value U_TFitting to obtain a first-order linear fitting formula; fitting the zero position a and the sensitivity b at different temperatures to obtain second-order linear fitting formulas a (T) and b (T).

When T is_A≤T≤T_BThe pressure output at T ℃ is:

the pressure output values of other temperature points of the sensor can be calculated by the formula (5), and the compensated pressure output value can be obtained by substituting the result into the formula (4).

The compensation results of each point after the algorithm compensation of the invention are shown in the following table 2:

TABLE 2 Algorithm Compensation results for points after temperature Compensation

The compensation results of the rest of temperature points compensated by the algorithm of the invention are shown in the following table 3:

TABLE 3 Compensation results of points after temperature compensation by linear interpolation algorithm

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution of the present invention and the inventive concept within the technical scope of the present invention.

Claims (3)

1. A compensation method for temperature drift of a silicon piezoresistive pressure sensor comprises the following steps:

1) in the temperature interval [ T₁，T₂]Inner, T₁、T₂Are all temperature values, and T₁<T₂Selecting a plurality of temperature points T, keeping the temperature T unchanged, collecting pressure output values under different pressures P, calculating a first-order linear formula of the pressure output values by a linear fitting method, and calculating each temperature by performing second-order linear fitting on a zero point a and a sensitivity b of each temperature point according to the first-order linear formulaSecond order fitting formulas a (T) and b (T) of the degree points, and obtaining zero points a corresponding to different temperature points T according to the second order fitting formulas a (T) and b (T)_TAnd sensitivity b_T；

2) In the temperature interval [ T₁，T₂]Setting a known selected fitting temperature point T, and judging the fitting temperature interval [ T ] in which the temperature point T is positioned₃，T₄]，T₁、T₂、T₃、T₄Are all temperature values, and T₁＜T₃≤T≤T₄＜T₂By the linear difference formulaCalculating the pressure output value U of the temperature point T_TWherein U is₃、U₄Respectively is a temperature point T₃、T₄A lower pressure output value;

3) calculating a compensated pressure output value U according to the formula (2)_T', in the formula (2), a₀Zero position of the sensor at ambient temperature, b₀Is the sensitivity of the sensor at normal temperature

${U_T}^{\&prime;}=a_0+\frac{U_T-a_T}{b_T}\&times;b_0---\left(2\right).$

2. The silicon piezoresistive pressure sensor of claim 1, having a temperature driftThe compensation method is characterized in that the first-order linear formula in the step 1) is shown as the formula (1), and a in the formula (1)_T、b_TRespectively the zero position and the sensitivity of the sensor at a certain temperature T ℃, and P is the measured pressure value of the sensor; u shape_TFor sensor pressure output value

U_T＝a_T+b_T×P (1)。

3. The method for compensating temperature drift of a silicon piezoresistive pressure sensor according to claim 2, wherein the second order fitting equations a (t) and b (t) in step 1) are respectively:

a(T)＝a₀+α(T-T₀)*Y(FS)

b(T)＝b₀+β(T-T₀)*Y(FS) (3)

wherein alpha is a zero temperature coefficient; beta is the sensitivity temperature coefficient, and Y (FS) is the full scale output value.