Pressure calibration method capable of being used for full temperature section based on conventional production calibration equipment

Abstract

The invention discloses a pressure calibration method capable of being used for a full temperature section based on conventional production calibration equipment, which effectively solves the technical problems of high production cost and low efficiency caused by the fact that the existing full temperature section pressure calibration seriously depends on expensive high and low temperature equipment by adopting a double-stage strategy of laboratory deep modeling and rapid production calibration. Specifically, the method only needs to collect subzero temperature data of a small amount of samples in a laboratory stage to construct a correction coefficient model, and can utilize conventional production calibration equipment only having a zero temperature test capability in a large-scale production stage. The offset parameter and the sensitivity parameter are corrected for the second time by collecting the calibration point data of the temperature section above zero and combining the correction coefficient, so that the equipment investment and the time cost are greatly reduced, the production takt is remarkably improved, and the production efficiency is improved on the premise that a low-temperature environment does not need to be configured on a production line. And the sensor is ensured to obtain a high-precision pressure calibration effect in a full temperature section (including a subzero low-temperature region).

Description

Technical Field

[0001] This invention relates to the field of pressure calibration technology, specifically to a pressure calibration method based on conventional production calibration equipment that can be used across the entire temperature range. Background Technology

[0002] Existing full-temperature-range calibration techniques for pressure sensors typically require data acquisition across the entire temperature range covering the sensor's operating range (including both above-zero and below-zero temperatures). Specifically, current techniques often require placing the MEMS (pressure sensor) sensing element to be calibrated in a high-low temperature test chamber and collecting data from the lowest below-zero operating temperature to the highest above-zero operating temperature, according to set temperature and pressure points. After acquiring sufficient raw data, calibration coefficients (such as zero-point drift, sensitivity, and nonlinearity compensation coefficients) for the entire temperature range are calculated using a fitting algorithm, and these coefficients are then burned into a signal conditioning chip.

[0003] However, the aforementioned existing technical solutions have significant technical problems: full-temperature range calibration places extremely high demands on production equipment and is inefficient. Conventional production calibration equipment (such as batch calibration benches) typically only has heating functions or, due to cost and size limitations, cannot provide a stable sub-zero temperature environment (e.g., -40°C or lower). Therefore, to achieve full-temperature range calibration, existing solutions must rely on expensive high and low temperature alternating test chambers for single-piece or small-batch testing. This not only results in high investment costs and large space requirements for calibration equipment, but also in lengthy heating and cooling processes, severely restricting production cycle time and failing to meet the demands for low cost and high efficiency in large-scale industrial production. If calibration is performed only in the upper-zero temperature range using conventional equipment, the sensor will experience a significant decrease in accuracy or even failure when operating in the lower-zero temperature range due to a lack of effective compensation. Summary of the Invention

[0004] This invention aims to provide a pressure calibration method that can be used across the entire temperature range based on conventional production calibration equipment. It adopts a two-stage strategy of in-depth laboratory modeling and rapid production calibration, which effectively solves the technical problem that existing pressure calibration methods for the entire temperature range heavily rely on expensive high and low temperature equipment, resulting in high production costs and low efficiency.

[0005] To achieve the above objectives, the technical solution adopted by this invention is as follows: a pressure calibration method based on conventional production calibration equipment that can be used across the entire temperature range, comprising the following steps:

[0006] Based on the calibration requirements, determine the temperature and pressure values ​​of the calibration points in the above-zero temperature range that need to be collected;

[0007] In the laboratory phase, for multiple MEMS sensing elements from the same batch, in addition to collecting calibration point data at temperatures above zero, data on zero-point pressure and maximum pressure at two sub-zero temperature points were also collected.

[0008] Based on the calibration point data of the above-zero temperature range, the calibration coefficient of each MEMS sensing element is calculated, and the offset parameter and sensitivity parameter of the two below-zero temperature points are calculated using the calibration coefficient;

[0009] Based on data collected at two sub-zero temperature points, the true offset and sensitivity parameters of each MEMS sensing element are calculated. The relationship between the deviation of the true offset and sensitivity parameters from the calculated offset and sensitivity parameters and temperature is modeled to obtain correction coefficients.

[0010] During the production stage, conventional production calibration equipment is used to collect pressure data at the calibration points in the above-zero temperature range, calculate calibration coefficients, and burn them into the signal conditioning chip. When the signal conditioning chip is operating at a sub-zero temperature, the calibration coefficients are first used to calculate the offset and sensitivity parameters, and then the offset and sensitivity parameters are corrected a second time according to the correction coefficients. Finally, the corrected parameters are used for pressure calibration.

[0011] Preferably, the calibration points for the above-zero temperature range include 3 temperature points and 4 pressure points. The 3 temperature points include a reference temperature point of 25°C, a low temperature point of 5°C, and a high temperature point of 85°C or 125°C. The 4 pressure points include a minimum range pressure point, a maximum range pressure point, and two equally spaced intermediate pressure points.

[0012] Preferably, the two sub-zero temperature points cover the lowest operating temperature of the chip, including the lowest operating temperature of the chip and a temperature point half the lowest operating temperature.

[0013] Preferably, the number of MEMS sensitive element samples collected in the laboratory stage is no less than 50 pieces.

[0014] Preferably, the modeling of the relationship between the deviation of the actual offset parameters and sensitivity parameters and the calculated offset parameters and sensitivity parameters and the temperature is to model the deviation as a first-order equation of the temperature difference between the current temperature and the reference temperature.

[0015] Preferably, when the signal conditioning chip operates at a temperature above zero, the pressure can be calibrated directly using the calibration coefficient without the need for secondary correction.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention employs a two-stage strategy of in-depth laboratory modeling and rapid production calibration, effectively solving the technical problem that existing pressure calibration across the entire temperature range heavily relies on expensive high and low temperature equipment, resulting in high production costs and low efficiency. Specifically, this method only requires collecting sub-zero temperature data from a small number of samples in the laboratory stage to construct a correction coefficient model. In the large-scale production stage, conventional production calibration equipment with only above-zero temperature testing capabilities can be used to collect calibration point data in the above-zero temperature range and combine it with correction coefficients to perform secondary correction on the offset and sensitivity parameters. Thus, without requiring the production line to be equipped with a low-temperature environment, it significantly reduces equipment investment and time costs, significantly improves production cycle time, and ensures that the sensor can obtain high-precision pressure calibration results across the entire temperature range (including the sub-zero temperature range). Attached Figure Description

[0018] Figure 1 This is a flowchart of a pressure calibration method based on conventional production calibration equipment that can be used across the entire temperature range. Detailed Implementation

[0019] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0020] To better illustrate this, let's first give some definitions related to pressure sensors:

[0021] Zero-point drift, in its physical sense, refers to the expected output voltage of a MEMS (pressure sensor) or the corresponding ADC RawData (code value) in the signal conditioning chip to be 0 when the pressure is 0 Pa. However, it is usually not 0; this offset is called zero-point drift. In practical applications, considering the linear operating range of the pressure sensor, if the minimum range of the pressure sensor is greater than 0 Pa, the minimum range value can be recorded as the zero-pressure point. Furthermore, zero-point drift has temperature characteristics; that is, at the same minimum pressure, the output voltage of the MEMS will differ at different temperatures. Its temperature characteristics are generally modeled as follows: (1).

[0022] Sensitivity (gain), in its physical sense, is the slope of the pressure sensor's reading before correction as a function of pressure: (2);

[0023] Sensitivity parameters also have temperature characteristics. These temperature characteristics are generally modeled as follows: (3);

[0024] Nonlinearity means that the output voltage of the MEMS does not increase linearly with the pressure value across the entire pressure range. It is generally modeled as follows:

[0025] (4);

[0026] (5);

[0027] Where offset is the zero-point drift parameter, and sensitivity is the sensitivity parameter. It is the difference between the calibration point temperature value and the reference temperature T0 (generally, the calibrated temperature value is used). This is the reference pressure point, which is the zero-point pressure selected during calibration. This refers to the ADC RawData value in the signal conditioning chip. This represents the actual pressure value.

[0028] In this embodiment, as Figure 1 As shown, this invention proposes a pressure calibration method applicable to the entire temperature range using conventional production calibration equipment. Because this invention performs secondary correction on the offset and sensitivity parameters in the sub-zero temperature range, and the correlation coefficient of this secondary correction only needs to be obtained based on laboratory test data, the calibration accuracy in the sub-zero temperature range can be significantly improved during the production stage using low-cost conventional production calibration equipment that only collects pressure data in the upper-zero temperature range. This invention does not require increasing costs by using more expensive production calibration equipment, nor does it reduce production efficiency. Specifically, it includes the following steps:

[0029] Based on the calibration requirements, determine the temperature and pressure values ​​of the calibration points in the above-zero temperature range that need to be collected;

[0030] Specifically, the pressure calibration points above zero temperature range need to be the same for both the laboratory and production stages. If high calibration accuracy is required, typically 3 temperature points and 4 pressure points are selected. If high calibration accuracy is not required, or if the MEMS itself has good temperature characteristics and linearity, only 2 temperature points and 3 pressure points can be selected. The above-zero temperature points are generally selected from three temperatures within the above-zero temperature range of the operating temperature. The middle temperature is used as a reference temperature, typically 25 degrees Celsius. The lowest above-zero temperature point is not recommended to be too close to 0 degrees Celsius; a low temperature point can generally be selected at 5 degrees Celsius. The high temperature point can be selected from the highest operating temperature supported by the chip, typically 85 or 125 degrees Celsius. The pressure points are typically selected from the chip's minimum operating pressure range, maximum operating pressure range, and two other pressure points in between, at equal intervals throughout the entire operating pressure range.

[0031] In the laboratory phase, for multiple MEMS sensing elements from the same batch, in addition to collecting calibration point data at temperatures above zero, data on zero-point pressure and maximum pressure at two sub-zero temperature points (e.g., -40°C and -20°C) are also collected. The selected sub-zero temperature points need to cover the lowest operating temperature of the chip; typically, the lowest operating temperature and half the lowest temperature point can be selected. To ensure sufficient statistical significance, data from at least 50 MEMS elements are collected.

[0032] Based on the calibration point data of the above-zero temperature range, the calibration coefficients of each MEMS sensing element are calculated according to formulas (1), (2), (3), (4), and (5), and the offset parameters and sensitivity parameters of the two below-zero temperature points are calculated using the calibration coefficients; denoted as: , Where n represents the MEMS designation.

[0033] Based on the data collected at two sub-zero temperature points, the actual offset parameters and sensitivity parameters of each MEMS sensing element are calculated according to formulas (1) and (2), and denoted as: , Furthermore, it models the relationship between the deviations of the actual offset parameters and sensitivity parameters from the calculated offset parameters and sensitivity parameters, and temperature, to obtain correction coefficients;

[0034] This can be modeled as a first-order equation:

[0035] (6);

[0036] (7);

[0037] By combining data from multiple MEMS chips, calculations are performed. Coefficient. Where dt is the difference between the current temperature and the reference temperature T0. The specific calculation process is as follows:

[0038] First, the average value of the relevant parameters at the corresponding temperature points for each MEMS chip is taken.

[0039] (8);

[0040] (9);

[0041] (10);

[0042] (11);

[0043] By combining the relevant data from two temperature points, a system of equations is constructed.

[0044] (12);

[0045] (13);

[0046] (14);

[0047] (15);

[0048] Solve the system of equations (11) and (12) and calculate... Coefficients; solve equations (14) and (15) and calculate Coefficients. Where dt1 and dt2 are the differences between two sub-zero temperature points and the reference temperature point, respectively.

[0049] During the production stage, conventional production calibration equipment is used to collect pressure data at the calibration points in the above-zero temperature range, calculate calibration coefficients, and burn them into the signal conditioning chip. In order to ensure that the coefficients calculated in the laboratory stage and the production stage are consistent, the calibration points used in the production stage and the process of calculating the coefficients must be completely consistent with those in the laboratory stage.

[0050] When the signal conditioning chip operates at sub-zero temperatures, the offset and sensitivity parameters are first calculated using the calibration coefficients. Then, the offset and sensitivity parameters are corrected a second time using the correction coefficients. Finally, the corrected parameters are used for pressure calibration. That is, based on the modeled correction equations, the two parameters are corrected a second time using formulas (6) and (7), respectively. The corrected parameters are then used for pressure calibration using formulas (4) and (5). When the signal conditioning chip operates at above-zero temperatures, the pressure is calibrated directly using the calibration coefficients without the need for secondary correction.

[0051] In another embodiment, the deviation between the actual and calculated values ​​of the offset and sensitivity parameters is modeled as a first-order equation for the temperature difference between the current temperature and the reference temperature. It can also be modeled as a second-order equation for the temperature difference, i.e.:

[0052] ;

[0053] .

[0054] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A pressure calibration method based on conventional production calibration equipment that can be used across the entire temperature range, characterized in that, Includes the following steps: Based on the calibration requirements, determine the temperature and pressure values ​​of the calibration points in the above-zero temperature range that need to be collected; In the laboratory phase, for multiple MEMS sensing elements from the same batch, in addition to collecting calibration point data at temperatures above zero, data on zero-point pressure and maximum pressure at two sub-zero temperature points were also collected. Based on the calibration point data of the above-zero temperature range, the calibration coefficient of each MEMS sensing element is calculated, and the offset parameter and sensitivity parameter of the two below-zero temperature points are calculated using the calibration coefficient; Based on data collected at two sub-zero temperature points, the true offset and sensitivity parameters of each MEMS sensing element are calculated. The relationship between the deviation of the true offset and sensitivity parameters from the calculated offset and sensitivity parameters and temperature is modeled to obtain correction coefficients. During the production stage, conventional production calibration equipment is used to collect pressure data at the calibration points in the above-zero temperature range, calculate calibration coefficients, and burn them into the signal conditioning chip. When the signal conditioning chip is operating at a sub-zero temperature, the calibration coefficients are first used to calculate the offset and sensitivity parameters, and then the offset and sensitivity parameters are corrected a second time according to the correction coefficients. Finally, the corrected parameters are used for pressure calibration.

2. The pressure calibration method based on conventional production calibration equipment, applicable to the entire temperature range, as described in claim 1, is characterized in that... The calibration points for the above-zero temperature range include 3 temperature points and 4 pressure points.

3. The pressure calibration method based on conventional production calibration equipment, applicable to the entire temperature range, as described in claim 2, is characterized in that... The three temperature points include a reference temperature of 25°C, a low temperature of 5°C, and a high temperature of 85°C or 125°C. The four pressure points include a minimum range pressure point, a maximum range pressure point, and two equally spaced pressure points in between.

4. The pressure calibration method based on conventional production calibration equipment, applicable to the entire temperature range, as described in claim 1, is characterized in that... The two sub-zero temperature points cover the lowest operating temperature of the chip, including the lowest operating temperature of the chip and half the lowest operating temperature.

5. A pressure calibration method based on conventional production calibration equipment applicable to the entire temperature range, as described in claim 1, is characterized in that... The number of MEMS sensitive element samples collected in the laboratory phase shall not be less than 50.

6. The pressure calibration method based on conventional production calibration equipment, applicable to the entire temperature range, as described in claim 1, is characterized in that... The modeling of the relationship between the deviation of the actual offset parameters and sensitivity parameters and the calculated offset parameters and sensitivity parameters and the temperature is to model the deviation as a first-order equation of the temperature difference between the current temperature and the reference temperature.

7. A pressure calibration method based on conventional production calibration equipment applicable to the entire temperature range, as described in claim 1, is characterized in that... When the signal conditioning chip operates at temperatures above zero, the pressure can be calibrated directly using the calibration coefficient, without the need for secondary correction.

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