Piston detection method and system of piston pressure gauge

Abstract

The invention provides a piston detection method and system for a piston pressure gauge, and relates to the technical field of laser measurement, and the system comprises a laser light source which is used for emitting a laser beam; the first reflecting mirror is arranged on a bearing disc of the standard piston pressure gauge; the second reflecting mirror is arranged on a bearing disc of the piston pressure gauge to be detected; the optical system is used for splitting the laser light source into a first transmission light beam and a first reflection light beam, enabling the first transmission light beam to irradiate the first reflector, enabling the first reflection light beam to irradiate the second reflector, and combining the light beam reflected by the first reflector and the light beam reflected by the second reflector to generate interference fringes; and the signal processing system is used for acquiring the interference fringes and analyzing the operation condition of the detected piston of the detected piston pressure gauge based on the displacement of the interference fringes. According to the invention, direct contact with a measured object is not needed, and errors and damage possibly caused by contact measurement are avoided. Moreover, the displacement change of the piston can be monitored in real time, and the measurement time is remarkably shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of laser measurement, and in particular to a piston detection method and system for a piston pressure gauge. Background Art

[0002] The piston descent speed of a piston pressure gauge refers to the speed at which the piston descends due to fluid leakage through the piston gap under a specified pressure. It is one of the key indicators for measuring the sealing performance of a piston pressure gauge, directly affecting the accuracy and reliability of pressure measurement. At the same time, it is also one of the necessary items for verification. An excessively fast piston descent speed usually indicates leakage, friction between the piston and the piston barrel, or that the seal has been worn or damaged. By measuring the piston descent speed, these problems can be detected in a timely manner, and corresponding maintenance measures can be taken to ensure that the sealing performance of the equipment meets the standard requirements. Summary of the Invention

[0003] In view of this, the present invention provides a piston detection method and system for a piston pressure gauge.

[0004] In a first aspect, an embodiment of the present invention provides a piston detection system for a piston pressure gauge, including: a laser light source for emitting a laser beam; a first reflector disposed on the load-bearing plate of a standard piston pressure gauge; a second reflector disposed on the load-bearing plate of the piston pressure gauge to be inspected; an optical system for splitting the laser light source into a first transmitted beam and a first reflected beam, irradiating the first transmitted beam onto the first reflector, irradiating the first reflected beam onto the second reflector, and combining the beams reflected by the first reflector and the second reflector to generate interference fringes; a signal processing system for acquiring the interference fringes and analyzing the operating condition of the piston to be inspected of the piston pressure gauge to be inspected based on the displacement amount of the interference fringes.

[0005] In a second aspect, an embodiment of the present invention provides a piston detection method for a piston pressure gauge, which is applied to the piston detection system for a piston pressure gauge described in any embodiment of the first aspect. The method includes: disposing the first reflector on the load-bearing plate of the standard piston pressure gauge and disposing the second reflector on the load-bearing plate of the piston pressure gauge to be inspected; connecting the standard piston pressure gauge and the piston pressure gauge to be measured and placing them in the working position, adjusting the initial weights of the standard piston of the standard piston pressure gauge and the piston to be inspected of the piston pressure gauge to be inspected to respectively compensate for the additional masses of the first reflector and the second reflector; when the standard piston pressure gauge and the piston pressure gauge to be measured reach pressure balance, acquiring the position or the number of fringes of the interference fringes; analyzing the change of the interference fringes based on the position or the number of fringes, and recording the number of fringe movements within a preset time period; calculating the displacement difference between the standard piston and the piston to be inspected based on the number of fringe movements; and analyzing the operating condition of the piston to be inspected of the piston pressure gauge to be inspected based on the displacement difference.

[0006] The piston detection method and system of the piston pressure gauge provided by the embodiments of the present invention are measured by the principle of optical interference, without direct contact with the object to be measured, avoiding the errors and damages that may be brought by contact measurement. Moreover, it can monitor the change of piston displacement in real time with high resolution, has high measurement accuracy, has an intuitive balance state indication function, is more sensitive to small displacement changes, can quickly judge the pressure magnitude relationship between the standard piston pressure gauge and the piston pressure gauge to be measured, and can significantly shorten the measurement time.

[0007] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0009] Figure 1 It is a schematic structural diagram of a piston detection system for a piston pressure gauge provided by an embodiment of the present invention; Figure 2 It is a schematic structural diagram of another piston detection system for a piston pressure gauge provided by an embodiment of the present invention; Figure 3 It is a flowchart of a piston detection method for a piston pressure gauge provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0010] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0011] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can also be the internal communication of two components. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0012] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0013] Please refer to Figure 1 , Figure 1 FIG. is a schematic structural diagram of a piston detection system for a piston pressure gauge provided by an embodiment of the present invention. The piston detection system mainly includes: a laser light source 1, a first reflector 2, a second reflector 3, an optical system 4, and a signal processing system 5. Among them, the laser light source 1 is used to emit a laser beam. In practical applications, helium-neon lasers or semiconductor lasers can be used, with stable wavelengths and good monochromaticity. In this embodiment, the piston detection system is mainly used to detect the operating conditions of the piston to be tested of the piston pressure gauge to be tested. In order to detect this operating condition, detection is achieved by comparing a standard piston pressure gauge with the piston pressure gauge to be tested.

[0014] To implement the detection process of this embodiment, the first reflector 2 is disposed on the load-bearing plate of the standard piston pressure gauge to reflect the light irradiated thereon; the second reflector 3 is disposed on the load-bearing plate of the piston pressure gauge to be tested to reflect the light irradiated thereon. In practical applications, the surface of the load-bearing plate of the piston pressure gauge is not necessarily very flat, and its reflection of the irradiated light may be relatively scattered. Therefore, in order to obtain relatively consistent reflected light, in this embodiment, for the piston pressure gauge to be tested and the standard pressure gauge, reflectors are respectively disposed on their load-bearing plates to form relatively complete and consistent reflected light.

[0015] In some alternative embodiments of the embodiments of the present invention, when calibrating the piston pressure gauge, a reflector needs to be temporarily installed on the piston rod to form an interference optical path. However, the mass of the reflector will change the mass ratio of the piston system (including the piston rod, the load-bearing plate, and the weights), resulting in a pressure calculation error (pressure P = F / A, where the force F = mg, and the mass change directly affects the pressure value. F is the vertical force applied to the piston or the object to be measured, usually generated by the gravity of the weights (F = mg, m is the mass of the weights, g is the acceleration due to gravity; A is the effective acting area of the piston or the object to be measured, that is, the contact area for pressure transmission)). After calibration, the reflector needs to be removed, but it is necessary to ensure that the system mass returns to the original state after removal to avoid re-calibration. Therefore, the starting balance method needs to be used, and by pre-adjusting the initial counterweight (weights) of the piston, the additional mass of the reflector is compensated, so that: When installing the reflector: the total mass (original mass M + reflector mass m) = the original calibration mass M. That is: by reducing the weight mass m, so that M 新 = M - m, and the total mass after installing the reflector returns to M.

[0016] After removing the mirror: the total mass returns to M 新 = M - m, but since the mirror has been removed, the actual mass M 实际 = M 新 + m = M, which is consistent with the original calibration state.

[0017] In this embodiment, the initial balancing process achieved by the above-mentioned initial balancing method can make it unnecessary to impose special restrictions on the mass of the mirror in practical applications. Regardless of the size relationship between the mass of the weights and the mass of the mirror, it can be applied. Moreover, even if the mass of the mirror is less than 20% of the range of the piston pressure gauge, it can still meet the detection requirements, and the applicable range is wide.

[0018] The optical system 4 is used to split the laser light source into a first transmitted beam and a first reflected beam, make the first transmitted beam irradiate on the first mirror 2, make the first reflected beam irradiate on the second mirror 3, and combine the beams reflected by the first mirror 2 and the second mirror 3 to generate interference fringes. In practical applications, during the transfer process of the piston pressure gauge, the difference in the descending speed between the piston pressure gauge under test and the standard piston pressure gauge means that there is a small error in the pressure values of the two. Moreover, this difference indicates that the pistons do not descend synchronously, which will cause a change in the optical path, thereby causing the movement of the interference fringes.

[0019] The signal processing system 5 is used to obtain the interference fringes and analyze the operating conditions of the piston under test of the piston pressure gauge under test based on the displacement amount of the interference fringes. By accurately measuring the movement amount of the interference fringes, the difference in the descending speed of the pistons between the piston pressure gauges can be calculated, and the accurate transfer of the piston value can be achieved by using the high resolution of the interferometer. And based on the difference in this descending speed, the gap between the movement of the piston of the piston pressure gauge under test and the movement of the standard piston can be determined, so as to judge whether there is a problem with the piston under test.

[0020] Piston pressure gauges with different accuracy grades have different requirements for the descending speed. For example: Grade 0.005: The descending speed is not greater than 0.15 mm / min (the upper limit of the measurement range is 0.6 MPa).

[0021] Grade 0.01: The descending speed is not greater than 0.2 mm / min (the upper limit of the measurement range is 6 MPa).

[0022] Grade 0.02: The descending speed is not greater than 0.3 mm / min (the upper limit of the measurement range is 25 MPa).

[0023] Currently, the minimum piston descending speed that can be measured is 0.01 mm / min, which is difficult to meet the transfer requirements of higher-grade piston pressure gauges. Through the detection system of this embodiment, higher-precision displacement changes can be detected to meet the detection requirements of different grades.

[0024] The piston detection system of the piston pressure gauge provided by the embodiment of the present invention measures through the above process by the principle of optical interference, without direct contact with the object to be measured, avoiding errors and damages that may be caused by contact measurement. Moreover, it can monitor the change of piston displacement in real time, is suitable for dynamic measurement, can significantly shorten the measurement time, and does not require several hours as in the traditional method to measure the tiny downward displacement of the piston.

[0025] In some alternative embodiments of the embodiment of the present invention, the optical system 4 mainly includes: a beam splitting prism 41, a reflecting mirror 42, and a compensating mirror 43.

[0026] Among them, the beam splitting prism 41 is used to split the laser light source into a first transmitted beam and a first reflected beam. Among them, the first transmitted beam irradiates the reflecting mirror 42 through the compensating mirror 43, and the first reflected beam irradiates the first reflecting mirror 2; the first reflecting mirror 2 is used to reflect the first reflected beam so that the reflected second reflected beam irradiates the beam splitting prism 41; the reflecting mirror 42 is used to reflect the first transmitted beam and reflect the third reflected beam reflected back by the second reflecting mirror 3 so that the third reflected beam irradiates the beam splitting prism 41 through the compensating mirror 43; the beam splitting prism 41 is further used to combine the second reflected beam and the third reflected beam into interference fringes. The compensating mirror 43 is mainly used to offset the optical path and dispersion differences introduced by the beam splitting prism 41 and offset the half-wave loss.

[0027] In some alternative embodiments of the embodiment of the present invention, as Figure 2 shown, the piston detection system of the piston pressure gauge may further include a beam expander 6, and the beam expander 6 is used to expand the laser beam emitted by the laser light source 1.

[0028] In some alternative embodiments of the embodiment of the present invention, the signal processing system 5 includes: a photodetector and a data processing unit. Among them, the photodetector is used to obtain the interference fringes; the data processing unit is used to calculate the displacement amount of the interference fringes and analyze the operating condition of the piston to be inspected of the piston pressure gauge to be inspected based on the displacement amount.

[0029] In some alternative embodiments of the embodiment of the present invention, as Figure 2 shown, the signal processing system 5 includes: an observation screen 51, a CCD camera 52, and a computer terminal 53. Among them, the observation screen 51 is used to display the interference fringes; the CCD camera 52 is used to detect the number of movements of the interference fringes; the computer terminal 53 is used to calculate the displacement amount of the interference fringes based on the number of movements and analyze the operating condition of the piston to be inspected of the piston pressure gauge to be inspected based on the displacement amount.

[0030] Further, the piston detection system of the piston pressure gauge may further include: an adjustment module for adjusting the counterweight of the piston under test to make the descending speeds of the standard piston and the piston under test consistent; correspondingly, the signal processing system 5 is further configured to calculate the average speed based on the accumulated displacement. The displacement difference data is obtained from the displacements acquired through multiple repeated measurements to calculate the average speed, which can be used to characterize the stability of the piston pressure gauge under test. Exemplarily, the number of interference fringe movements N of the standard piston and the piston under test at different time points can be recorded, and through the formula , the displacement difference between different pistons can be calculated. Wherein, represents the wavelength of the laser light source. Then, the average displacement difference is calculated by combining the displacement differences obtained from multiple measurements. Then, through the formula , the average value of the piston movement speed is calculated, where t is the time interval.

[0031] For further reference Figure 3 , as an implementation of the systems shown in the above figures, the present invention provides an embodiment of a piston detection method for a piston pressure gauge. This device embodiment corresponds to the Figure 1 shown system embodiment, and this method can be specifically applied to the piston detection system of the piston pressure gauge described in any of the above embodiments.

[0032] As Figure 3 shown, the piston detection method 300 of the piston pressure gauge in this embodiment includes: Step 301: Set the first reflector on the load disk of the standard piston pressure gauge, and set the second reflector on the load disk of the piston pressure gauge under test. Before performing this step, some basic initialization operations can also be performed. For example, ensure the stability of the optical path and mechanical structure. Adjust the optical path to make the interference fringes clearly visible, and calibrate the interferometer to ensure its good working state.

[0033] Step 302: Pre-adjust the initial counterweights of the standard piston of the standard piston pressure gauge and the piston under test of the piston pressure gauge under test respectively to compensate for the additional masses of the first reflector and the second reflector. When calibrating the piston pressure gauge, a reflector needs to be temporarily installed on the piston rod to form an interference optical path. However, the mass of the reflector will change the total mass of the piston system (including the piston rod, load disk, and weights), resulting in a pressure calculation error (pressure P = F / A, where the force F = mg, and the change in mass directly affects the pressure value. F is the vertical force applied to the piston or the object under test, usually generated by the gravity of the weights (F = mg, m is the mass of the weights, g is the acceleration due to gravity; A is the effective acting area of the piston or the object under test, that is, the contact area for pressure transmission)). After calibration, the reflector needs to be removed, but it is necessary to ensure that the system mass returns to the original state after removal to avoid re-calibration. Therefore, the starting balance method needs to be used to compensate for the additional mass of the reflector by pre-adjusting the initial counterweights (weights) of the pistons.

[0034] Step 303: Place the standard piston pressure gauge and the piston pressure gauge to be tested in a rotation equilibrium position, and obtain the position or the number of fringes of the interference fringes.

[0035] Step 304: Analyze the change of the interference fringes based on the position or the number of fringes, and record the number of fringe movements N within a preset time period t.

[0036] Step 305: Calculate the displacement difference between the standard piston and the piston to be inspected based on the number of fringe movements. According to the formula , the displacement difference between different pistons can be calculated. Wherein, represents the wavelength of the laser light source.

[0037] Step 306: Analyze the operating condition of the piston to be inspected of the piston pressure gauge to be tested based on the displacement difference. By accurately measuring the movement amount of the interference fringes, the difference in the piston descent speed between the piston pressure gauges can be calculated, and the high resolution of the interferometer is used to achieve accurate piston value transfer. And based on the difference in the descent speed, the gap between the movement of the piston of the piston pressure gauge to be tested and the movement of the standard piston can be determined, so as to judge whether there is a problem with the piston to be inspected.

[0038] Furthermore, in order to calibrate the piston to be inspected, the counterweight of the piston to be inspected can also be adjusted, and steps 303 to 306 are repeated to make the descent speeds of the standard piston and the piston to be inspected consistent. And, the average speed can be calculated based on the accumulated displacement. The displacement difference data obtained from the displacements obtained by multiple repeated measurements are used to calculate the average speed, which can be used to characterize the stability of the piston pressure gauge to be tested. Exemplarily, the number of interference fringe movements N of the standard piston and the piston to be inspected at different time points can be recorded, and through the formula , the displacement difference between different pistons can be calculated. Wherein, represents the wavelength of the laser light source. Then, the average value of the displacement differences is calculated by combining the displacement differences obtained from multiple measurements. Then, through the formula calculate the average value of the piston movement speed, where t is the time interval.

[0039] This embodiment exists as a method embodiment corresponding to the above system embodiment. The piston detection method of the piston pressure gauge provided in this embodiment is measured through the optical interference principle, without direct contact with the object to be measured, avoiding the errors and damages that may be brought by contact measurement. And, the change of the piston displacement can be monitored in real time, which is suitable for dynamic measurement, can significantly shorten the measurement time, and does not require the traditional method to take several hours to measure the tiny descent displacement of the piston.

[0040] In some alternative embodiments of this embodiment, the situations that cause the interference fringes to move may include the following: (1)Synchronous descent of the piston under test and the reference piston due to leakage.

[0041] In this case, if the two pistons descend synchronously due to leakage and at the same speed, the optical path changes of the two paths are similar, and the optical path difference hardly changes. Correspondingly, the interference fringes are stationary or slowly drifting. By recognizing that the interference fringes remain stationary or the distance moved within a preset time duration is less than a preset value, it can be determined that a leakage situation has occurred.

[0042] (2)Descent caused by excessive weights on the piston under test.

[0043] In this case, the piston under test moves downward, extending its optical path, and the reference piston moves upward, shortening its optical path, resulting in an increase in the total optical path difference. If the initial direction of the fringes is vertical, an increase in the optical path difference will cause the interference fringes to move in the horizontal direction; if the initial direction of the fringes is horizontal, an increase in the optical path difference will cause the interference fringes to move in the vertical direction.

[0044] (3)Descent caused by excessive weights on the reference piston.

[0045] In this case, the reference piston moves downward and the piston under test moves upward, resulting in a decrease in the total optical path difference. If the initial direction of the fringes is vertical, a decrease in the optical path difference will cause the interference fringes to move in the horizontal direction; if the initial direction of the fringes is horizontal, a decrease in the optical path difference will cause the interference fringes to move in the vertical direction.

[0046] The detection devices used in the prior art usually rely on digital display. By reading the numbers and combining with the absolute position of the current piston disc, addition and subtraction of positions are performed to make judgments. It can be seen that the above process is relatively cumbersome and has low efficiency. However, through the piston detection method of the piston pressure gauge and the piston detection system of the piston pressure gauge provided in this embodiment, there is no need to obtain specific values during detection, and various situations that cause the movement of interference fringes can be identified faster and more effectively, and the identification accuracy is also higher.

[0047] Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) that contain computer-usable program codes.

[0048] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device generate means for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0049] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0050] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0051] Obviously, the above embodiments are merely examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A piston detection system for a piston pressure gauge, characterized in that Comprising: A laser light source for emitting a laser beam; A first reflector disposed on the load-bearing plate of a standard piston pressure gauge; A second reflector disposed on the load-bearing plate of the piston pressure gauge to be tested; An optical system for splitting the laser light source into a first transmitted beam and a first reflected beam, causing the first transmitted beam to irradiate the first reflector, causing the first reflected beam to irradiate the second reflector, and combining the beam reflected by the first reflector and the beam reflected by the second reflector to generate interference fringes; A signal processing system for acquiring the interference fringes and analyzing the operating condition of the piston to be tested of the piston pressure gauge to be tested based on the displacement amount of the interference fringes.

2. The system according to claim 1, wherein The optical system includes: a beam splitting prism, a reflecting mirror, and a compensating mirror, wherein, The beam splitting prism is used to split the laser light source into the first transmitted beam and the first reflected beam. Among them, the first transmitted beam irradiates the reflecting mirror through the compensating mirror, and the first reflected beam irradiates the first reflector; The first reflector is used to reflect the first reflected beam, causing the reflected second reflected beam to irradiate the beam splitting prism; The reflecting mirror is used to reflect the first transmitted beam and reflect the third reflected beam reflected back by the second reflector, causing the third reflected beam to irradiate the beam splitting prism through the compensating mirror; The beam splitting prism is further used to combine the second reflected beam and the third reflected beam into the interference fringes.

3. The system according to claim 2, wherein The optical system further includes: A beam expander for expanding the laser beam emitted by the laser light source.

4. The system according to claim 1, wherein The signal processing system includes: A photodetector for acquiring the interference fringes; A data processing unit for calculating the displacement amount of the interference fringes and analyzing the operating condition of the piston to be tested of the piston pressure gauge to be tested based on the displacement amount.

5. The system according to claim 1, wherein The signal processing system includes: An observation screen for displaying the interference fringes; A CCD camera for detecting the number of movements of the interference fringes; A computer terminal for calculating the displacement amount of the interference fringes based on the number of movements and analyzing the operating condition of the piston to be tested of the piston pressure gauge to be tested based on the displacement amount.

6. The system according to claim 1, wherein Further comprising: An adjustment module for adjusting the counterweight of the piston to be tested so that the descending speeds of the standard piston and the piston to be tested are the same; The signal processing system is further used to calculate the average speed based on the accumulated displacement amount.

7. A piston detection method for a piston pressure gauge, applied to the piston detection system of the piston pressure gauge according to any one of claims 1-6, characterized in that, Comprising: Disposing the first reflector on the load-bearing plate of a standard piston pressure gauge and disposing the second reflector on the load-bearing plate of the piston pressure gauge to be tested; Pre-adjusting the initial counterweights of the standard piston of the standard piston pressure gauge and the piston to be tested of the piston pressure gauge to be tested, respectively compensating for the additional masses of the first reflector and the second reflector; Placing the standard piston pressure gauge and the piston pressure gauge to be tested in a rotationally balanced position, acquiring the position or the number of fringes of the interference fringes; Analyzing the change of the interference fringes based on the position or the number of fringes, and recording the number of fringe movements within a preset time period; Calculating the displacement difference between the standard piston and the piston to be tested based on the number of fringe movements; Analyze the operating condition of the piston under test of the piston gauge to be tested based on the displacement difference.

8. The method according to claim 7, wherein It further includes: Adjust the counterweight of the piston under test to make the descent speeds of the standard piston and the piston under test consistent; Calculate the average speed based on the accumulated displacement.

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