Multi-source pressure sensor range calibration method

Abstract

The invention relates to the technical field of sensors, in particular to a multi-source pressure sensor range calibration method, a multi-source pressure sensor is adopted for measurement, the multi-source pressure sensor at least comprises sensitive structures with two measuring ranges, and each sensitive structure is connected with a corresponding detection circuit. A user selects one sensitive structure for measurement according to a required measuring range, and the process of calibrating the measured value of the sensitive structure comprises the following steps: setting a temperature calibration point and a pressure calibration point; obtaining an equation obtained by fitting a normalized voltage value output by a temperature sensitive resistor of a temperature sensor in the current circuit, a normalized voltage value output by a voltage sensing bridge and the voltage calibration point according to the calibration point; and inputting the measured normalized voltage value output by the temperature-sensitive resistor and the normalized voltage value output by the voltage-sensing bridge into an equation obtained by fitting, and outputting a calibrated pressure value. According to the invention, the corresponding sensitive structure can be matched according to the actual pressure detection range to reduce the influence of environmental factors.

Description

Technical Field

[0001] The invention relates to the technical field of sensors, and in particular to a range calibration method for a multi-source pressure sensor. Background Art

[0002] Vacuum refers to the state of gas below a standard atmospheric pressure. The measurement of vacuum is widely used in industrial equipment and instruments such as semiconductor manufacturing, advanced material processing, aerospace, nuclear power generation, and energy transportation. At present, different detection technologies have their own advantages and disadvantages at different vacuum levels. Therefore, the use of appropriate sensitive structures for detection of different vacuum ranges can greatly reduce the influence of various factors such as temperature, humidity, and power supply fluctuations, so as to improve the stability of the sensor and the detection accuracy.

[0003] Among many environmental factors, temperature changes have the greatest impact on sensors. The most common temperature compensation method at present is direct temperature compensation, that is, a thermistor powered by a constant current source collects voltage data at multiple points for voltage fitting temperature. However, in actual detection, the constant current source may fluctuate with changes in temperature, and the coefficients of the polynomial in the obtained second-order voltage fitting formula are very large. When the output voltage of the thermistor fluctuates for some reason, it will seriously affect the actual temperature obtained by fitting, resulting in a large error, which will seriously affect the stability and detection accuracy of the sensor. Summary of the invention

[0004] In order to solve the problem of the influence of temperature change on the accuracy of the pressure sensor and realize multi-range or full-range high-precision pressure detection, the present invention provides a multi-source pressure sensor range calibration method, which uses a multi-source pressure sensor for measurement. The multi-source pressure sensor includes at least two sensitive structures with different ranges and each sensitive structure is connected to its corresponding detection circuit. The user selects a sensitive structure for measurement according to the required range. The process of calibrating the measured value of the sensitive structure includes the following steps:

[0005] Set the temperature calibration point and the pressure calibration point, and obtain the equation obtained by fitting the normalized voltage value output by the thermistor of the temperature sensor in the current circuit and the normalized voltage value output by the pressure-sensitive bridge with the voltage calibration point according to the calibration point;

[0006] The measured normalized voltage value output by the temperature-sensitive resistor and the normalized voltage value output by the pressure-sensitive bridge are input into the fitted equation, and the calibrated pressure value is output.

[0007] Furthermore, the process of obtaining the normalized voltage value output by the temperature-sensitive resistor of the temperature sensor in the current circuit and the normalized voltage value output by the pressure-sensitive bridge according to the calibration point and fitting the equation obtained by the voltage calibration point includes:

[0008] Apply the force of the pressure calibration point to the sensitive structure, obtain the actual measurement value of the sensitive structure at the pressure calibration point, and use the pressure calibration point as output and the measurement value as input to perform fitting using a linear equation;

[0009] Using the slope and zero point of the linear equation obtained by fitting at each temperature calibration point, quadratic fitting is performed to obtain a quadratic equation of temperature, the slope and zero point of the linear equation;

[0010] The current temperature is calculated according to the normalized voltage value output by the thermistor, the current temperature is input into the quadratic equation of the slope and the zero point to obtain the corresponding slope and the zero point, and a linear equation is established according to the obtained slope and the zero point;

[0011] The measured value obtained according to the current sensitive structure is input into the established linear equation to obtain the calibrated pressure value.

[0012] Furthermore, the current temperature value is obtained through a current calibration method.

[0013] Furthermore, the process of obtaining the current temperature value by the current calibration method includes:

[0014] The resistance value of the thermistor at different temperatures can be obtained through the resistance value and temperature relationship table provided by the thermistor;

[0015] The output voltage of the temperature-sensitive resistor at the temperature is measured, and the current is calculated by dividing the voltage by the resistance to obtain the fitting curve of current and voltage at different temperatures;

[0016] Substitute the output voltage of the measured thermistor into the fitting curve to obtain the relevant current, divide the voltage by the current to obtain the resistance, and then obtain the current actual temperature through the relationship between the resistance value of the thermistor and the temperature.

[0017] Furthermore, the process of obtaining the equation obtained by fitting the normalized voltage value output by the thermistor of the temperature sensor in the current circuit, the normalized voltage value output by the pressure-sensitive bridge and the voltage calibration point according to the calibration point includes: directly fitting the normalized voltage value output by the thermistor as the x-axis, the normalized voltage value output by the pressure-sensitive bridge as the y-axis, and the voltage calibration point as the z-axis.

[0018] Furthermore, the sensitive structure includes a piezoresistive pressure sensor, a Pirani pressure sensor, and a resonant pressure sensor.

[0019] Furthermore, a sensitive structure in the multi-source pressure sensor is selected to be in a normally open state and other sensitive structures are in a normally closed state, and a judgment is made based on the measurement value of the sensitive structure in the normally open state. If the measurement value of the sensitive structure in the normally open state exceeds its measurement range, the sensitive structure in the normally open state is closed and the sensitive structure in the corresponding range is opened.

[0020] The present invention can match the corresponding sensitive structure according to the actual pressure detection range to reduce the influence of environmental factors, and at the same time use the current calibration method to obtain a more accurate actual temperature to achieve high-stability and high-precision measurement of the pressure in the corresponding range. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flow chart of a pressure sensor range calibration method according to an embodiment of the present invention;

[0022] Figure 2 is a fitting curve diagram of the normalized value of the pressure-sensitive bridge voltage and the actual pressure in an embodiment of the present invention;

[0023] Figure 3 It is a fitting curve diagram of the normalized value of the pressure-sensitive bridge voltage and the actual pressure at different temperatures in an embodiment of the present invention;

[0024] Figure 4 is a fitting curve diagram of the direct temperature compensation method of an embodiment of the present invention;

[0025] Figure 5 It is a fitting curve diagram of the current calibration temperature compensation method according to an embodiment of the present invention;

[0026] Figure 6 It is a fitting curve diagram of the slope of the actual temperature and pressure calibration curve of the embodiment of the present invention;

[0027] Figure 7 It is a fitting curve diagram of the zero point of the actual temperature and pressure calibration curve of the embodiment of the present invention;

[0028] Figure 8 It is a fitting curve diagram of the normalized output voltage of the temperature-sensitive resistor, the normalized output voltage value of the pressure-sensitive bridge and the actual pressure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] 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.

[0030] The present invention provides a multi-source pressure sensor range calibration method, which uses a multi-source pressure sensor for measurement. The multi-source pressure sensor includes at least two sensitive structures with different ranges, and each sensitive structure is connected to a corresponding detection circuit. A user selects a sensitive structure for measurement according to the required range. The process of calibrating the measured value of the sensitive structure includes the following steps:

[0031] Set the temperature calibration point and the pressure calibration point, and obtain the equation obtained by fitting the normalized voltage value output by the thermistor of the temperature sensor in the current circuit and the normalized voltage value output by the pressure-sensitive bridge with the voltage calibration point according to the calibration point;

[0032] The normalized voltage value of the temperature-sensitive resistor output and the normalized voltage value of the pressure-sensitive bridge output currently measured are input into the fitted equation, and the calibrated pressure value is output.

[0033] like Figure 1 The process of obtaining the normalized voltage value output by the temperature-sensitive resistor of the temperature sensor in the current circuit and the normalized voltage value output by the pressure-sensitive bridge and the equation obtained by fitting the voltage calibration point according to the calibration point includes:

[0034] Apply the force of the pressure calibration point to the sensitive structure, obtain the actual measurement value of the sensitive structure at the pressure calibration point, and use the pressure calibration point as output and the measurement value as input to perform fitting using a linear equation;

[0035] Using the slope and zero point of the linear equation obtained by fitting at each temperature calibration point, quadratic fitting is performed to obtain a quadratic equation of temperature, the slope and zero point of the linear equation;

[0036] The current temperature is calculated according to the normalized voltage value output by the thermistor, the current temperature is input into the quadratic equation of the slope and the zero point to obtain the corresponding slope and the zero point, and a linear equation is established according to the obtained slope and the zero point;

[0037] The measured value obtained according to the current sensitive structure is input into the established linear equation to obtain the calibrated pressure value.

[0038] In a specific embodiment of the present invention, a piezoresistive sensitive structure is used as an example to illustrate the signal calibration method; under the condition of constant voltage power supply, constant temperature and humidity, the fitting curve between the normalized value of the pressure-sensitive bridge voltage and the actual pressure is measured as follows: Figure 2 As shown, the fitted linear equation is expressed as y=69.506x+1.0783, where x represents the normalized value of the output voltage of the pressure-sensitive bridge, and y represents the actual pressure; the horizontal axis in the figure is the normalized value of the output voltage of the pressure-sensitive bridge, and the vertical axis is the actual pressure. The fitting curve is obtained by first-order polynomial fitting, which proves that the relationship between the two is basically linear and can be fitted by a linear function. Such a first-order calibration equation can be in the following form:

[0039] Y=A×X+B

[0040] Among them, Y is the actual value of pressure, X is the voltage signal output by the sensitive structure, A is the slope of the calibration curve at different temperatures, and B is the zero point value of the calibration curve at different temperatures.

[0041] At different standard temperature values, the fitting curves of the normalized value of the pressure-sensing bridge voltage and the actual pressure are as follows: Figure 3 As shown, the abscissa is 0.2, and the three fitting lines with decreasing actual pressure values ​​are expressed as:

[0042] Fitting line 1: y = 78.99x + 1.1879, temperature 60°C

[0043] Fitting line 2: y = 64.861x + 1.0063, temperature 0°C

[0044] Fitting line 3: y = 54.188x + 0.8556, temperature -45°C

[0045] It can be seen from the above curve that when the temperature remains unchanged, the output voltage of the Wheatstone pressure-sensitive bridge is basically linearly related to the actual pressure, and the fitting curve can be obtained through a first-order function; at the same time, temperature is the main indicator affecting the pressure output. As the temperature rises, the fitting curve of voltage and pressure will "rise", that is, the slope increases, and the zero point depends on the characteristics of the sensor itself.

[0046] In the direct temperature compensation method, the piezoresistive pressure sensor usually has a thermistor for sensing temperature. The resistance of the thermistor has a definite relationship with the temperature. It is powered by a constant current source, collects multi-point voltage data, and directly uses the voltage to fit the temperature. Generally, the second order can meet the requirements.

[0047] This embodiment uses PT100 thermal resistor as an example for testing. Figure 4 It is a fitting curve diagram of the normalized value of thermistor output voltage and the actual temperature, that is, the direct temperature compensation method. The horizontal axis in the figure is the normalized value of thermistor output voltage, and the vertical axis is the actual temperature. The fitting curve is obtained by fitting a second-order polynomial, which proves that the relationship between thermistor output voltage and pressure can basically be fitted by a second-order function, which is expressed as:

[0048] y=1047.1x 2 -944.01x+121.35

[0049] In the fitting formula, the polynomial coefficient is very large. When the normalized value of the thermistor output voltage on the horizontal axis fluctuates for some reason, it will seriously affect the actual temperature obtained by fitting and cause a large error.

[0050] Since the relationship between the resistance value and temperature of the temperature sensitive resistor is determined and reliable in the long term, the measurement of digital quantity can only characterize the resistance by measuring the voltage. Generally, a constant current source is used to power the temperature sensitive resistor, but the constant current source may fluctuate with changes in temperature. That is, although the direct temperature calibration method is simple to use and has a small amount of calculation, when the constant current source is not stable enough, there will be a problem that the relationship between voltage and temperature cannot be directly fitted with a polynomial to achieve a higher accuracy.

[0051] Therefore, a current calibration temperature compensation method is proposed, such as Figure 5 It is the fitting curve of the normalized output voltage of the temperature sensitive resistor and the current, that is, the current calibration temperature compensation method; the horizontal axis in the figure is the normalized value of the output voltage of the temperature sensitive resistor, and the vertical axis is the calculated current, which is expressed as:

[0052] y=-0.0101x 2 +0.0073x+0.0076

[0053] It can be seen from the above formula that: as the temperature rises, the voltage output by the thermistor increases, and the current will have a certain monotonic decrease, which proves that the constant current source decreases regularly with the increase of temperature, and the law has a certain universality.

[0054] Taking a test of the CG-SK1A temperature and pressure sensor as an example, the output voltage of the pressure-sensitive bridge and the corresponding actual pressure at multiple standard temperature points were collected to obtain the fitting curves at different temperatures, and then the slope and zero point of the fitting curve were obtained.

[0055] The fitting curve of the slope of the actual temperature and pressure calibration curve is shown in Figure 6 In the figure, the horizontal axis is the actual temperature, and the vertical axis is the slope of the pressure calibration curve, which is expressed as y=0.2355x+64.802; the fitting curve of the actual temperature and the zero point of the pressure calibration curve is shown in Figure 7 In the figure, the horizontal axis is the actual temperature, and the vertical axis is the zero point of the pressure calibration curve, which is expressed as y=-0.000006x+0.0033x+0.9964. It can be seen that the slope and zero point of the pressure calibration curve increase with the increase of temperature, and the slope and zero point of the pressure calibration curve at each temperature point can be obtained accordingly.

[0056] The actual temperature can be calculated by measuring the output voltage of the thermistor, and the slope and zero point of the pressure calibration curve can be calculated based on the actual temperature. By substituting the slope and zero point into the calibration curve, the output voltage of the pressure-sensitive bridge can be calculated to obtain the actual pressure.

[0057] The fitting curves of the normalized output voltage of the temperature sensitive resistor of the CG-SK1A temperature and pressure sensor, the normalized output voltage of the pressure sensing bridge and the actual pressure are shown in Figure 8 In the figure, the x-axis is the normalized output voltage of the temperature-sensitive resistor, the y-axis is the normalized output voltage of the pressure-sensitive bridge, and the z-axis is the actual pressure. The z-axis output is expressed as:

[0058] z=-7.009+28.81x+86.64y-370.4x 2 -202.2xy+0.3836y 2 +17.04x 3 +233.1x 2 y-1.877y2

[0059] It can be seen from the above formula that good results can also be obtained directly through three-dimensional polynomial fitting.

[0060] The sensitive structure of the above example is a piezoresistive type, which can also include Pirani type, resonant type and other sensitive structures, and each sensitive structure corresponds to a different range segment and is equipped with corresponding driving and acquisition circuits; at the same time, for the mutual interference problem of detection signals of multi-source sensitive structures and the problem of high detection power consumption, a sensitive structure can be selected as a normally open pressure detection module, and its detected pressure signal value is first judged by the microprocessor through a threshold, and an analog switch is used to realize the signal acquisition control of different sensitive structures.

[0061] To sum up, the multi-source pressure sensor range calibration method provided by the present invention sets up a detection core with multiple sensitive source structures, corresponding to high-precision and wide-range pressure detection in multiple range segments, and each range segment is configured with a corresponding calibration equation. Users can choose different sensitive structures, range segments and calibration equations according to different application scenarios, and calibrate and output the initial pressure signal according to the corresponding calibration equation. This product has a wide range of use and high precision, and different range segments can be selected according to actual application requirements to achieve high-precision pressure measurement within the full range.

[0062] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "outside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0063] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "rotation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0064] 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 multi-source pressure sensor range calibration method, characterized in that: A multi-source pressure sensor is used for measurement. The multi-source pressure sensor includes at least two sensitive structures with different measuring ranges and each sensitive structure is connected to its corresponding detection circuit. The user selects a sensitive structure for measurement according to the required measuring range. The process of calibrating the measured value of the sensitive structure includes the following steps: Set the temperature calibration point and the pressure calibration point, and obtain the equation obtained by fitting the normalized voltage value output by the thermistor of the temperature sensor in the current circuit and the normalized voltage value output by the pressure-sensitive bridge with the voltage calibration point according to the calibration point; The normalized voltage value of the temperature-sensitive resistor output and the normalized voltage value of the pressure-sensitive bridge output currently measured are input into the fitted equation, and the calibrated pressure value is output.

2. A multi-source pressure sensor range calibration method according to claim 1, characterized in that: The process of obtaining the normalized voltage value output by the temperature-sensitive resistor of the temperature sensor in the current circuit and the normalized voltage value output by the pressure-sensitive bridge according to the calibration point and the equation obtained by fitting the voltage calibration point includes: Apply the force of the pressure calibration point to the sensitive structure, obtain the actual measurement value of the sensitive structure at the pressure calibration point, and use the pressure calibration point as output and the measurement value as input to perform fitting using a linear equation; Using the slope and zero point of the linear equation obtained by fitting at each temperature calibration point, quadratic fitting is performed to obtain a quadratic equation of temperature, the slope and zero point of the linear equation; The current temperature is calculated according to the normalized voltage value output by the thermistor, the current temperature is input into the quadratic equation of the slope and the zero point to obtain the corresponding slope and the zero point, and a linear equation is established according to the obtained slope and the zero point; The measured value obtained according to the current sensitive structure is input into the established linear equation to obtain the calibrated pressure value.

3. A multi-source pressure sensor range calibration method according to claim 2, characterized in that: The current temperature value is obtained through the current calibration method.

4. A multi-source pressure sensor range calibration method according to claim 3, characterized in that: The process of obtaining the current temperature value through the current calibration method includes: The resistance value of the thermistor at different temperatures can be obtained through the resistance value and temperature relationship table provided by the thermistor; The output voltage of the temperature-sensitive resistor at the temperature is measured, and the current is calculated by dividing the voltage by the resistance to obtain the fitting curve of current and voltage at different temperatures; Substitute the output voltage of the measured thermistor into the fitting curve to obtain the relevant current, divide the voltage by the current to obtain the resistance, and then obtain the current actual temperature through the relationship between the resistance value of the thermistor and the temperature.

5. A multi-source pressure sensor range calibration method according to claim 2, characterized in that: The process of obtaining the equation obtained by fitting the normalized voltage value output by the thermistor of the temperature sensor in the current circuit, the normalized voltage value output by the pressure-sensitive bridge and the voltage calibration point according to the calibration point includes: directly fitting the normalized voltage value output by the thermistor as the x-axis, the normalized voltage value output by the pressure-sensitive bridge as the y-axis, and the voltage calibration point as the z-axis.

6. A method for calibrating the range of a multi-source pressure sensor according to claim 1, characterized in that: The sensitive structures include piezoresistive pressure sensors, Pirani pressure sensors, and resonant pressure sensors.

7. A multi-source pressure sensor range calibration method according to claim 1, characterized in that: A sensitive structure in the multi-source pressure sensor is selected to be in a normally open state and other sensitive structures are in a normally closed state, and a judgment is made based on the measurement value of the sensitive structure in the normally open state. If the measurement value of the sensitive structure in the normally open state exceeds its measurement range, the sensitive structure in the normally open state is closed and the sensitive structure in the corresponding range is opened.

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