A temperature compensation method for silicon pressure sensor

Abstract

The present invention relates to the field of sensor technology, and discloses a temperature compensation method for a silicon pressure sensor, comprising the steps of first defining a set of parameters, collecting data, collecting the output and bridge voltage values ​​of the pressure sensor at different temperature points and different pressure points, and observing whether the output data and bridge voltage data of the sensor increase monotonically or decrease monotonically with the reference pressure value. The temperature compensation method for the silicon pressure sensor uses the result of mathematical operation of the output of the sensor and the bridge voltage as temperature information to perform temperature compensation on the sensor, so that the temperature information of the pressure sensor is insensitive to the pressure information, thereby improving the temperature compensation accuracy of the pressure sensor. Compared with the method of using an external temperature sensor for temperature measurement compensation, the hardware overhead used in the present invention is less, and the temperature gradient problem of the external temperature sensor and the pressure sensor is overcome. The method can improve the accuracy of the sensor in a rapid temperature change environment.

Description

Technical Field

[0001] The invention relates to the technical field of sensors, and in particular to a temperature compensation method for a silicon pressure sensor. Background Art

[0002] Silicon piezoresistive pressure sensor is made by using the piezoresistive effect of single crystal silicon. Four semiconductor resistors of equal value are diffused in a specific direction of the silicon diaphragm and connected to form a Wheatstone bridge, which serves as the sensitive element of the force-electricity converter. When the diaphragm is subjected to external pressure and the bridge loses balance, if an excitation power supply (constant current and constant voltage) is added to the bridge, an output voltage proportional to the measured pressure can be obtained, thereby achieving the purpose of measuring pressure.

[0003] The output of silicon piezoresistive pressure sensor changes with the change of external environment temperature. In order to improve the accuracy of most silicon piezoresistive pressure sensors in actual use, temperature compensation is required. It is a common method to use a single-chip microcomputer to collect, process and temperature compensate the output of silicon piezoresistive pressure sensor. However, in the actual production and manufacturing process of silicon piezoresistive pressure sensor, due to processing errors and process consistency problems, it is impossible to achieve complete symmetry. Therefore, the bridge resistance value is not only related to temperature, but also has a certain correlation with pressure. Due to processing errors, the bridge resistance is used as a temperature parameter for temperature compensation. The bridge resistance is sensitive to temperature and pressure, which affects the compensation accuracy. The method of using an external temperature sensor for temperature compensation can improve the accuracy of temperature compensation, but it will increase hardware overhead. When the sensor works in a rapid temperature change environment, the temperature gradient between the pressure chip and the temperature sensor will affect the accuracy. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the deficiencies in the prior art, the present invention provides a temperature compensation method for a silicon pressure sensor, which has the advantages of performing mathematical operations on the bridge resistance and pressure sensor output voltage obtained by testing, utilizing their monotonic characteristics that change with pressure, to obtain a set of data that is related to temperature and not related to pressure, and using these data as temperature compensation, thereby solving the problem that the output of the existing silicon piezoresistive pressure sensor changes with the change of the external ambient temperature. In order to improve the accuracy of most silicon piezoresistive pressure sensors in actual use, temperature compensation is required, but due to processing errors and process consistency issues, complete symmetry cannot be achieved, which affects the final data obtained.

[0006] (II) Technical solution

[0007] To achieve the above object, the present invention provides the following technical solution: a temperature compensation method for a silicon pressure sensor; comprising the steps;

[0008] S1: First define a set of parameters and collect data;

[0009] S2: At different temperature points and pressure points, the output of the pressure sensor and the bridge voltage value are collected. P is the sensor output data; T is the bridge voltage data.

[0010] S3: Observe whether the output data of the sensor and the bridge voltage data increase or decrease monotonically with the reference pressure value, and obtain the intermediate array M;

[0011] S4: define the coefficient of each temperature and calculate the mean value Havg;

[0012] S5: Calculate the intermediate array M*Havg+P, obtain the array Temp, and obtain the mean.

[0013] Preferably, the defined parameters are A1, A2, ..., AN representing N temperature values, which can be obtained by a temperature device;

[0014] B1, B2, BM represent M reference pressure values, which can be obtained by a high-precision pressure controller, PACE5000 series, after a certain period of pressure maintenance.

[0015] Preferably, the output of the pressure sensor and the bridge voltage value are collected. Since the bridge voltage value can reflect the size of the bridge resistance when the current source is powered, the bridge resistance can be represented by the bridge voltage. If the voltage source is powered, the sampling resistor voltage connected in series with the Wheatstone bridge is measured to infer the size of the bridge resistance.

[0016] Preferably, the coefficients H1, H2, ...HN at each temperature are defined, and the calculation formula is: HN = (MAX(PN1, PN2, ...PNM)-MIN(PN1, PN2, ...PNM)) / (MAX(TN1, TN2, ...TNM)-MIN(TN1, TN2, ...TNM)), and the average Havg of all coefficients H1, H2, ...HN is taken.

[0017] Preferably, the corresponding elements in Temp at each temperature AN are taken and the average is taken to represent the temperature value at that temperature, and the temperature compensation is obtained by using linear interpolation, cubic spline interpolation or polynomial fitting algorithm using the data.

[0018] Preferably, observe whether the output data of the sensor and the bridge voltage data increase monotonically or decrease monotonically as the reference pressure value increases. If the monotonicity of the sensor output and the bridge voltage is the same, subtract each bridge voltage collection data from a positive integer that is one digit greater than all the bridge voltage collection data and is divisible by 10 to obtain an intermediate array M; if the monotonicity of the sensor output and the bridge voltage is different, the bridge voltage collection data is directly regarded as the intermediate array M.

[0019] Preferably, the output data collected by the sensor and the bridge voltage data collected are both completed by a single chip microcomputer and are dimensionless numbers.

[0020] (III) Beneficial effects

[0021] Compared with the prior art, the present invention provides a temperature compensation method for a silicon pressure sensor, which has the following beneficial effects:

[0022] The temperature compensation method of the silicon pressure sensor uses the result of mathematical operation between the output of the sensor and the bridge voltage as temperature information to perform temperature compensation on the sensor, so that the temperature information of the pressure sensor is insensitive to the pressure information, thereby improving the temperature compensation accuracy of the pressure sensor. Compared with the method of using an external temperature sensor for temperature measurement compensation, the hardware overhead used in the present invention is less, and the temperature gradient problem of the external temperature sensor and the pressure sensor is overcome. This method can improve the accuracy of the sensor in a rapid temperature change environment, and the temperature compensation method can be extended to other sensors based on the piezoresistive effect and the strain effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the Wheatstone bridge in the present invention;

[0024] Figure 2 This is a graph of bridge voltage acquisition data in the present invention;

[0025] Figure 3 This is a temperature data diagram after processing in the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Embodiment 1

[0028] A temperature compensation method for a silicon pressure sensor; comprising the steps;

[0029] S1: First define a set of parameters and collect data;

[0030] S2: At different temperature points and pressure points, the output of the pressure sensor and the bridge voltage value are collected. P is the sensor output data; T is the bridge voltage data.

[0031] S3: Observe whether the output data of the sensor and the bridge voltage data increase or decrease monotonically with the reference pressure value, and obtain the intermediate array M;

[0032] S4: define the coefficient of each temperature and calculate the mean value Havg;

[0033] S5: Calculate the intermediate array M*Havg+P, obtain the array Temp, and obtain the mean;

[0034] The parameters defined by S1 are A1, A2, ... AN representing N temperature values, which can be obtained by a temperature device;

[0035] B1, B2, BM represent M reference pressure values, which can be obtained by a high-precision pressure controller. For the PACE5000 series, the reference pressure value is reached after a certain period of pressure maintenance. The S1 also includes the S11, which collects the output of the pressure sensor and the bridge voltage value. Since the bridge voltage value can reflect the size of the bridge resistance when the current source is powered, the bridge resistance can be represented by the bridge voltage. If the voltage source is used for power supply, the voltage of the sampling resistor connected in series with the Wheatstone bridge is measured, and the bridge resistance can be calculated. The S4 also includes S41, which defines the coefficients H1, H2, ... HN at each temperature, and the calculation formula is: HN = (MAX (PN1, PN2, ... PNM) - MIN (PN1, PN2, ... PNM)) / (MAX (TN1, TN2, ... TNM) - MIN (TN1, TN2, ... TNM)), take the average value Havg of all coefficients H1, H2, ... HN, S4 and S5 also include S51, S51 takes each The corresponding elements in Temp under the temperature AN are averaged to represent the temperature value at the temperature. The temperature compensation is obtained by using the data using linear interpolation, cubic spline interpolation or polynomial fitting algorithm. The S6 also includes S61. The measurement pressure range of the S61 sensor is 70kPa to 1080kPa, and the temperature range is -55℃ to 85℃. The S3 also includes S31. The S31 observes whether the output data of the sensor and the bridge voltage data increase monotonically or decrease monotonically as the reference pressure value increases. If the monotonicity of the sensor output and the bridge voltage is the same, then subtract each bridge voltage acquisition data from a positive integer that is one digit greater than all the bridge voltage acquisition data and is divisible by 10 to obtain the intermediate array M; if the monotonicity of the sensor output and the bridge voltage is different, the bridge voltage acquisition data is directly regarded as the intermediate array M; if the monotonicity of the sensor output and the bridge voltage is different, the bridge voltage acquisition data is directly regarded as the intermediate array M. The sensor output acquisition data and the bridge voltage acquisition data are both completed by the single-chip microcomputer and are dimensionless numbers.

[0036] See also Figure 1-3 , P11, P12, P1M and T11, T12, T1M, respectively represent the sensor output acquisition data and bridge voltage acquisition data at different reference pressure values ​​at temperature A1;

[0037] P21, P22, P2M and T21, T22, T2M respectively represent the sensor output acquisition data and bridge voltage acquisition data at different reference pressure values ​​at temperature A2;

[0038] PN1, PN2, ...PNM and TN1, TN2, ...TNM respectively represent the sensor output acquisition data and bridge voltage acquisition data at different reference pressure values ​​at temperature AN;

[0039] All sensor output data can be abbreviated as array P in order from front to back, and all bridge voltage data can be abbreviated as T in order from front to back, which is the data of the sensor taken;

[0040]

[0041]

[0042] Sensors collect data;

[0043]

[0044]

[0045] Linear interpolation, cubic spline interpolation or polynomial fitting algorithms can all calculate values ​​that are not in the table during the table lookup process, which can improve the accuracy of the data.

[0046] Actual measurement results of the sensor;

[0047]

[0048]

[0049]

[0050] The output of the sensor has the same monotonicity as the bridge voltage, and the maximum value of all bridge voltage acquisition data is 1635662, which is divisible by 10, and the data with the largest digit is 10000000, so by subtracting each bridge voltage from 10000000, we can get the array M. The H1, H2, H3, H4, and H5 of the sensor are 145.198, 147.885, 142.448, 114.430, and 157.124 respectively, so Havg=141.417, and the intermediate array can be calculated: M*Havg+P, and the data processing result table can be obtained;

[0051]

[0052]

[0053] A single-chip microcomputer is an integrated circuit chip that uses ultra-large-scale integrated circuit technology to integrate a central processing unit (CPU) with data processing capabilities, random access memory (RAM), read-only memory (ROM), multiple I / O ports and interrupt systems, timers / counters, and other functions. Therefore, it can record sensor data and bridge voltage data very well. Figure 2 and Figure 3 It can be clearly seen that at the same temperature, when the pressure changes, the bridge voltage output has a certain slope. If these data are used for temperature compensation, errors will occur. Figure 2 This is the data processed by the algorithm of the present invention. It can be seen that at the same temperature, when the pressure changes, the data is insensitive to the pressure change, which proves the effectiveness of the algorithm. The result of the mathematical operation of the sensor output and the bridge voltage is used as temperature information to perform temperature compensation on the sensor, so that the temperature information of the pressure sensor is insensitive to the pressure information, thereby improving the temperature compensation accuracy of the pressure sensor. Compared with the method of using an external temperature sensor for temperature compensation, the hardware overhead used in the present invention is less, and the temperature gradient problem of the external temperature sensor and the pressure sensor is overcome. This method can improve the accuracy of the sensor in a rapid temperature change environment, and the temperature compensation method can be extended to other sensors based on piezoresistive effect and strain effect.

[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A temperature compensation method for a silicon pressure sensor, Features: Includes steps: S1: First define a set of parameters and collect data; S2: At different temperature points and pressure points, the output of the pressure sensor and the bridge voltage value are collected. P is the sensor output data; T is the bridge voltage data. S3: Observe whether the output data of the sensor and the bridge voltage data increase or decrease monotonically with the reference pressure value, and obtain the intermediate array M; S4: define the coefficient of each temperature and calculate the mean value Havg; S5: Calculate the intermediate array M*Havg+P, obtain the array Temp, and obtain the mean; The parameters defined by S1 are A1, A2, ..., AN representing N temperature values, which can be obtained by temperature equipment; B1, B2, BM representing M reference pressure values, which can be obtained by a high-precision pressure controller and reached after a certain period of pressure maintenance; The S1 also includes the S11, which collects the output of the pressure sensor and the bridge voltage value. Since the bridge voltage value can reflect the size of the bridge resistance when the current source is powered, the bridge resistance can be represented by the bridge voltage. If the voltage source is used for power supply, the voltage of the sampling resistor connected in series with the Wheatstone bridge is measured to deduce the size of the bridge resistance. The S3 also includes S31, wherein the S31 observes whether the output data of the sensor and the bridge voltage data increase monotonically or decrease monotonically as the reference pressure value increases. If the monotony of the sensor output and the bridge voltage is the same, then each bridge voltage acquisition data is subtracted from a positive integer that is one digit greater than all bridge voltage acquisition data and is divisible by 10 to obtain an intermediate array M; if the monotony of the sensor output and the bridge voltage is different, the bridge voltage acquisition data is directly regarded as the intermediate array M; S5 also includes S51, which takes the corresponding elements in Temp at each temperature AN and takes the average to characterize the temperature value at that temperature, and uses linear interpolation, cubic spline interpolation or polynomial fitting algorithm to obtain temperature compensation using the data.

2. The temperature compensation method of a silicon pressure sensor according to claim 1, Features: S4 also includes S41, which defines the coefficients H1, H2, ...HN at each temperature, and the calculation formula is: HN = (MAX(PN1, PN2, ...PNM)-MIN(PN1, PN2, ...PNM)) / (MAX(TN1, TN2, ...TNM)-MIN(TN1, TN2, ...TNM)), and the average value Havg of all coefficients H1, H2, ...HN is taken.

3. The temperature compensation method of a silicon pressure sensor according to claim 1, Features: The sensor output data and bridge voltage data are collected by the microcontroller and are dimensionless numbers.

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