Fine calibration method and device for pressure sensor

Abstract

This invention discloses a precise calibration method and apparatus for pressure sensors, belonging to the field of fluid pressure measurement. The method includes: providing a calibration system comprising a reference tank, on which a reference device and a pressure sensor to be calibrated are mounted; the inlet of the reference tank is connected to a gas source, and the outlet is connected to a standard leak; adjusting the pressure inside the reference tank to the upper or lower limit of the pressure range to be calibrated; opening the channel from the outlet of the reference tank to the standard leak, allowing the pressure to change slowly through the standard leak; during the pressure change process, reading the pressure value of the reference device in real time and writing it correspondingly to the sensor being calibrated, achieving continuous calibration. The pressure change process is controlled according to the formula ΔP=(Q * t) / V, where V is the volume of the reference tank, Q is the leakage rate of the standard leak, t is the leakage time, and ΔP is the pressure change. This invention utilizes the continuity of pressure changes caused by leakage from the standard leak to achieve automatic, continuous, and precise control of the pressure point for pressure sensor calibration. It can perform high-density data acquisition and curve fitting for any range of the sensor, significantly improving calibration accuracy, and the apparatus is simple and low-cost.

Description

Technical Field

[0001] This invention belongs to the field of fluid pressure measurement technology, specifically relating to a fine calibration method and apparatus for a pressure sensor, which is particularly suitable for continuous and high-precision calibration of a certain range of the sensor. Background Technology

[0002] Pressure sensors must be calibrated after manufacturing to determine the correspondence between their output and input pressures. Traditional calibration methods typically involve manually or automatically adjusting a pressure regulating valve (such as a precision pressure reducing valve or a proportional valve) to establish several discrete pressure points, then comparing these points with a standard pressure reference (such as a high-precision digital pressure gauge), and finally writing the standard value into the sensor.

[0003] This traditional method has the following drawbacks: It can only calibrate discrete pressure points and cannot obtain the continuous pressure response characteristics of the sensor throughout the entire range. In particular, it is difficult to capture small nonlinear changes near certain key pressure points.

[0004] The control accuracy of the pressure point is limited by the accuracy and stability of the regulating valve, making it difficult to achieve precise and repeatable pressure settings.

[0005] The control system is complex, requiring the valve to be adjusted while reading the reference and the sensor being calibrated. It usually requires closed-loop feedback control, which is costly and cumbersome to debug.

[0006] In the prior art, there are also devices that utilize standard leaks for gas flow or leakage detection. For example, patent document CN103323182A discloses a leak calibration device that calculates the leak rate by filling a calibration container of known volume with gas and measuring the rate of pressure change over time. This technology focuses on the calibration of the leak itself and does not address how to use a standard leak to calibrate a pressure sensor.

[0007] Therefore, there is a need for a method and apparatus for continuous, high-precision, and simple pressure sensor calibration. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a fine calibration method and device for pressure sensors. By utilizing the leakage of a standard orifice to continuously control the pressure change within the calibration system, continuous calibration of pressure points can be achieved, thereby improving calibration accuracy and efficiency.

[0009] The technical solution adopted in this invention is: A method for fine calibration of a pressure sensor includes the following steps: A calibration system is provided, the system including a reference tank, on which a reference device and a pressure sensor to be calibrated are mounted, the inlet of the reference tank is connected to a gas source via a pipeline, and the outlet of the reference tank is connected to a standard leak via a pipeline. Adjust the pressure inside the reference tank to the upper or lower limit of the pressure range to be calibrated; Open the channel from the outlet of the reference tank to the standard leak hole, so that the pressure inside the reference tank can slowly leak to the atmosphere through the standard leak hole, and the pressure changes continuously; During pressure changes, the pressure value of the reference device is read in real time through the calibration system, and this pressure value is written into the pressure sensor as a standard value to complete the continuous calibration of the pressure sensor.

[0010] As a further improvement of the present invention, the pressure change process is controlled according to the formula ΔP = (Q * t) / V, where V is the volume of the reference tank, Q is the leakage rate of the standard leak, t is the leakage time, and ΔP is the pressure change within time t. This quantitative relationship allows for precise prediction and control of pressure changes during the calibration process.

[0011] Preferably, when the pressure range to be calibrated is a positive pressure, the pressure inside the reference tank is adjusted to the upper limit of the pressure range to be calibrated, and then leaked through the standard leak hole until it is equal to atmospheric pressure; when the pressure range to be calibrated is a negative pressure, the pressure inside the reference tank is adjusted to the lower limit of the pressure range to be calibrated, and then air is filled into the reference tank through the standard leak hole until it reaches atmospheric pressure.

[0012] Preferably, the relationship between the volume V of the reference tank, the leakage rate Q of the standard leak, and the pressure change rate is: pressure change rate ΔP / Δt = Q / V. The pressure change rate can be controlled by selecting standard leaks with different leakage rates Q or by changing the volume V of the reference tank to adapt to different accuracy requirements and calibration efficiency needs.

[0013] Preferably, the calibration system continuously collects data from multiple pressure points during pressure changes and performs curve fitting on the collected data to obtain the characteristic curve of the pressure sensor, thereby achieving multi-point calibration or continuous curve calibration.

[0014] The present invention also provides a pressure sensor calibration device for implementing the above method, comprising: Gas source; The reference tank has its inlet connected to the gas source via a pipeline; The reference device is mounted on the reference tank; The calibrated pressure sensor is installed on the reference tank; A standard leak hole, the inlet of which is connected to the outlet of the reference tank via a pipe; The calibration system is electrically connected to the reference device and the pressure sensor being calibrated, respectively, and is used to read the pressure value of the reference device and write the value to the pressure sensor being calibrated.

[0015] Furthermore, a pressure regulating valve and a shut-off valve are sequentially installed on the pipeline between the gas source and the reference tank for setting and cutting off the initial pressure.

[0016] Furthermore, a shut-off valve is installed on the pipeline between the outlet of the reference tank and the standard leak hole to control the start and stop of leakage.

[0017] The beneficial effects of this invention are: It enables automatic and continuous variation of the pressure point for pressure sensor calibration, overcoming the limitation of traditional methods that can only calibrate discrete points, and can obtain the continuous response characteristics of the sensor within the full range or a specified range.

[0018] The rate of pressure change is determined by the leakage rate of the standard orifice and the volume of the reference tank. Both are highly controllable physical quantities, so the pressure control is highly accurate and repeatable, making it particularly suitable for fine calibration of the key range of the sensor.

[0019] The system has a simple structure, requires no complex closed-loop pressure control circuit, is low in cost, and is easy to operate.

[0020] By continuously acquiring data and curve fitting, the density and accuracy of calibration data can be significantly improved.

[0021] This invention combines the core structure of "standard leak + reference tank" with other components to form a complete calibration device technical solution. Even though the calibration system itself can be implemented using existing technologies known in the art, the overall technical solution formed by combining it with the aforementioned core structure is novel and produces a synergistic effect—utilizing the known leakage rate characteristics of the standard leak, continuous and high-precision calibration of the pressure sensor is achieved, which is a combination method not disclosed in the prior art. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the principle structure of the pressure sensor calibration device of the present invention.

[0023] In the diagram: 1. Gas source, 2. Pressure regulating valve, 3. Shut-off valve, 4. Reference tank, 5. Reference device, 6. Sensor to be calibrated, 7. Calibration system, 8. Shut-off valve, 9. Standard leak hole. Detailed Implementation

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] like Figure 1 As shown, the pressure sensor calibration device provided by the present invention includes: a gas source 1, which is connected to a pressure regulating valve 2 and a shut-off valve 3 in sequence through pipelines and then enters a reference tank 4; a reference device 5 (e.g., a high-precision digital pressure gauge) and a pressure sensor 6 to be calibrated are installed on the reference tank 4; the outlet of the reference tank 4 is connected to a shut-off valve 8, and a standard leak hole 9 is connected after the shut-off valve 8; the calibration system 7 is connected to the reference device 5 and the sensor 6 to be calibrated respectively through cables, and is used to read the pressure data of the reference device 5 and write the calibration parameters into the sensor 6 to be calibrated.

[0027] The calibration system 7 is a conventional data acquisition and processing unit. Its implementation can utilize a host computer, data acquisition card, or embedded system known in the art. It is used to read the output signals of the reference unit 5 and the calibrated sensor 6, perform data processing, and write the calibration coefficients into the calibrated sensor 6. The specific circuitry and software implementation are not innovative aspects of this invention; those skilled in the art can select appropriate existing technologies to implement it according to actual needs.

[0028] The specific implementation process of the calibration method of the present invention is as follows: Example 1: Fine Calibration of a Positive Pressure Sensor Assuming the range of the sensor 6 being calibrated is 0–1 MPa, it needs to be continuously calibrated across its full range.

[0029] First, close shut-off valve 8 and open shut-off valve 3. Adjust the pressure of gas source 1 to 1MPa using pressure regulating valve 2 to stabilize the pressure in reference tank 4 at 1MPa (full-scale pressure). Then close shut-off valve 3 to cut off the gas source.

[0030] Next, the shut-off valve 8 is opened, and the gas in the reference tank 4 slowly leaks into the atmosphere through the standard leak hole 9. The pressure in the reference tank 4 gradually decreases from 1 MPa to atmospheric pressure (approximately 0.1 MPa, with a relative pressure of 0).

[0031] During the leakage process, the pressure change strictly follows the formula ΔP = (Q * t) / V, where V is the volume of the reference tank 4, Q is the leakage rate of the standard leak hole 9, t is the leakage time, and ΔP is the pressure change within time t. The pressure change rate ΔP / Δt = Q / V is a constant, meaning the pressure changes linearly with time.

[0032] For example, if the volume of the reference tank 4 is V = 1L (i.e., 0.001m³), then... 3 The leakage rate Q = 1 × 10⁻⁶ is selected. -6 Pa·m 3 With a standard leak rate of / s, the pressure change rate is 0.001 Pa / s, meaning a change of only 3.6 Pa per hour, enabling extremely high-density data acquisition. To accelerate calibration, a leak with a higher leak rate can be used, such as Q=1×10⁻⁶.-3 Pa·m 3 If the change rate is 1 Pa / s, then the rate of change is 1 Pa / s.

[0033] During the pressure drop, the calibration system 7 continuously reads the pressure value of the reference device 5 (as the standard value) at a certain sampling frequency, and simultaneously reads the output value of the sensor being calibrated 6 (or directly writes the standard value into the sensor). Because the pressure changes continuously and slowly, the calibration system 7 can collect data from tens of thousands of pressure points. By performing curve fitting on these data, a high-precision characteristic curve of the sensor can be obtained throughout the entire measurement range, thus completing fine calibration.

[0034] Example 2: Fine Calibration of a Negative Pressure (Vacuum) Sensor If the sensor being calibrated is a vacuum sensor with a range of 101 kPa to 0 kPa (absolute pressure), the pressure inside the reference tank 4 needs to be evacuated to near vacuum during calibration (e.g., by replacing the gas source 1 with a vacuum pump, or by evacuating first and then filling with gas). Specific operation: Close the shut-off valve 8, open the shut-off valve 3, use a vacuum source to adjust the pressure inside the reference tank 4 to near zero absolute pressure, and then close the shut-off valve 3. Open the shut-off valve 8, and external air slowly enters the reference tank 4 through the standard leak hole 9 (i.e., reverse leakage), with the pressure gradually rising from low to high to atmospheric pressure. At this time, the pressure change also follows ΔP = (Q * t) / V, where Q is the leakage rate of air through the standard leak hole 9. The calibration system 7 also continuously collects data from the reference device 5 and the sensor being calibrated 6 during the pressure change process to complete the calibration.

[0035] Example 3: Fine calibration of key measurement ranges If only the sensor's accuracy within a specific pressure range (e.g., 0.8–1.0 MPa) is of concern, fine calibration can be performed only for that range. In this case, the initial pressure can be set to 1.0 MPa, and the shut-off valve 8 can be closed after leakage to 0.8 MPa, collecting data only for that range; alternatively, by replacing the standard leak orifice 9 with one of different leakage rates Q, the pressure change rate in that range can be slowed down (e.g., by using a leak orifice with a smaller leakage rate), thus obtaining more densely packed data points.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fine calibration of a pressure sensor, characterized in that, Includes the following steps: A calibration system is provided, the system including a reference tank (4), a reference device (5) and a pressure sensor (6) to be calibrated are installed on the reference tank (4), the inlet of the reference tank (4) is connected to a gas source (1) through a pipeline, and the outlet of the reference tank (4) is connected to a standard leak hole (9) through a pipeline. Adjust the pressure inside the reference tank (4) to the upper or lower limit of the pressure range to be calibrated; Open the channel from the outlet of the reference tank (4) to the standard leak hole (9) so that the pressure inside the reference tank (4) slowly leaks to the atmosphere through the standard leak hole (9), and the pressure changes continuously; During the pressure change process, the pressure value of the reference device (5) is read in real time by the calibration system (7), and the pressure value is written into the pressure sensor (6) as a standard value to complete the continuous calibration of the pressure sensor (6).

2. The fine calibration method for a pressure sensor according to claim 1, characterized in that, The pressure change process is controlled according to the formula ΔP = (Q * t) / V, where V is the volume of the reference tank (4), Q is the leakage rate of the standard leak (9), t is the leakage time, and ΔP is the pressure change within time t.

3. The fine calibration method for a pressure sensor according to claim 1 or 2, characterized in that, When the pressure range to be calibrated is positive, the pressure in the reference tank (4) is adjusted to the upper limit of the pressure range to be calibrated, and then leaked through the standard leak hole (9) to equal atmospheric pressure; when the pressure range to be calibrated is negative, the pressure in the reference tank (4) is adjusted to the lower limit of the pressure range to be calibrated, and then gas is filled into the reference tank (4) through the standard leak hole (9) to atmospheric pressure.

4. The fine calibration method for a pressure sensor according to claim 2, characterized in that, The relationship between the volume V of the reference tank (4), the leakage rate Q of the standard leak (9), and the pressure change rate is: pressure change rate ΔP / Δt = Q / V. The pressure change rate can be controlled by selecting standard leaks (9) with different leakage rates Q or by changing the volume V of the reference tank (4).

5. The fine calibration method for a pressure sensor according to claim 1, characterized in that, The calibration system (7) continuously collects data from multiple pressure points during the pressure change process and performs curve fitting on the collected data to obtain the characteristic curve of the pressure sensor, thereby realizing multi-point calibration or continuous curve calibration.

6. The fine calibration method for a pressure sensor according to claim 1, characterized in that, The gas source (1) and the reference tank (4) are connected in sequence by a pressure regulating valve (2) and a shut-off valve (3). The pressure is adjusted to the required value by the pressure regulating valve (2) and then the shut-off valve (3) is closed.

7. A pressure sensor calibration apparatus for implementing the method according to any one of claims 1 to 6, characterized in that, include: Gas source (1); The reference tank (4) has its inlet connected to the gas source (1) via a pipeline. The reference device (5) is installed on the reference tank (4); The calibrated pressure sensor (6) is installed on the reference tank (4); A standard leak hole (9) has its inlet connected to the outlet of the reference tank (4) via a pipe; The calibration system (7) is electrically connected to the reference device (5) and the calibrated pressure sensor (6) respectively, and is used to read the pressure value of the reference device (5) and write the value to the calibrated pressure sensor (6).

8. The pressure sensor calibration device according to claim 7, characterized in that, A pressure regulating valve (2) and a shut-off valve (3) are sequentially installed on the pipeline between the gas source (1) and the reference tank (4).

9. The pressure sensor calibration device according to claim 7, characterized in that, A shut-off valve (8) is provided on the pipeline between the outlet of the reference tank (4) and the standard leak hole (9).

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