CN106705823A - Field calibration method for linear displacement sensor - Google Patents

Abstract

The invention relates to a sensor calibration method, in particular to an on-site calibration method for a linear displacement sensor. Step 1, connect and fix the universal caliper with the linear displacement sensor to ensure that the moving direction of the universal caliper is parallel to the moving direction of the linear displacement sensor; Step 2, connect and fix the moving parts of the universal caliper with the moving parts of the linear displacement sensor; Driven by the moving parts of the caliper, the moving parts of the linear displacement sensor move synchronously, read the standard displacement given by the general caliper and the output value of the linear displacement sensor at each calibration point, and calibrate the linear displacement sensor according to the above data. A method for on-site calibration of a linear displacement sensor is provided. The method is easy to install, accurate and fast in positioning, and has universal applicability.

Description

A Field Calibration Method for Linear Displacement Sensor

technical field

The invention relates to a sensor calibration method, in particular to an on-site calibration method for a linear displacement sensor.

Background technique

In aircraft development, a large number of principle tests, verification tests and comprehensive tests need to be done. Positioning measurement systems for large components; fatigue test benches, fuel oil test benches, hydraulic manipulation tests, and iron bird comprehensive test benches are all equipped with tens to hundreds of linear displacement sensors. According to the relevant requirements for the quality assurance of weapons and equipment development, the sensors (measuring instruments) used in the test need to be calibrated regularly.

The linearity of the positioning system of large components and the linear displacement sensor used on the test bench is usually between 0.1% and 0.5%, and the actual working stroke is generally not more than 500mm, which are distributed in various parts such as high places and narrow spaces of the test bench , presents a multi-angle posture in space. Before the sensor is installed and used, its static characteristic indicators are calibrated under the conditions of the calibration laboratory according to the corresponding national standards, industry standards or enterprise standards. However, when the sensors are installed on large-scale tooling and test benches, some sensors are solidified on the test bench, and there is a positioning relationship that does not allow disassembly; some are installed in special places (such as: high altitudes, narrow spaces) and are inconvenient to disassemble; some are missing Positioning datum, it is difficult to reset accurately after disassembly. Due to the huge workload of disassembly and installation caused by periodic calibration, problems such as batch inspection or test interruption caused by suspected sensor failure are very obvious. The installation and reset of the sensor is not accurate, which reduces the continuity and reliability of the test data. , Therefore, the experimenters put forward the urgent demand of on-site calibration sensor.

The specification of calibration technology for linear displacement sensors in China is relatively late, and the country officially promulgated and implemented JJF1035-2011 "Calibration Specifications for Linear Displacement Sensors" in December 2011. As for the on-site calibration method of the linear displacement sensor, it is currently in the research stage, and a complete system has not yet been formed.

Foreign on-site calibration uses a laser interferometer. Since the laser interferometer is an ultra-precision device with a standard size of laser wavelength, the working environment and installation adjustment requirements are relatively strict. From the perspective of engineering practice, a large number of sensors with a linearity of no more than 0.25% do not need to use high-end equipment and complicated methods, and only need a convenient and quick on-site calibration method that meets the accuracy requirements.

According to the patent retrieval, the prior art closest to the present invention includes: calibration using gauge block method, length measuring machine method, grating displacement sensor calibration device method and laser interferometer method.

Method 1: The paper "On-Site Calibration of Linear Displacement Sensors" was published in "Measurement Technology", Volume 33, Issue 5, 2013; Authors: Yang Mingjun, Gong Wei. Using the block method.

This paper analyzes the limitations of the currently commonly used calibration method that is regularly sent to the laboratory, proposes a simple calibration method for linear displacement sensors that is suitable for on-site use, and verifies its correctness through a large number of on-site calibration data.

The deficiency of described gauge block calibration method is:

1. Only the calibration of the horizontal state is realized, and it is not suitable for the calibration of the on-site sensor installed at any angle.

2. When calibrating, it is not guaranteed that the moving parts of the sensor (pull rod or rope) are continuously compressed or stretched in the current calibration direction. Obviously, when placing and taking out a gauge block of a certain size, it will inevitably cause the moving parts of the sensor to flex and sway at the point to be calibrated, which will bring in the return error and repeatability error of the sensor itself, which is a major factor in sensor calibration. Avoid (unless it is known that the repeatability and return errors of the sensor are small enough to be negligible relative to the linearity).

3. Although the accuracy of the gauge block is very high, the perpendicularity between the moving rod or the pull wire (rope) and the working surface of the gauge block and the measurement force are difficult to control, and the actual calibration accuracy is difficult to guarantee.

Method 2: The paper "The Method of Using Length Measuring Machine to Calibrate Pull-wire Displacement Sensor" was published on HowNet; Author: Wu Peigang. The length measuring machine method is adopted, and the grating or other scales on the length measuring machine are used as the length standard.

The disadvantage of the calibration method of the length measuring machine is that the body of the length measuring machine needs to be at a level when it is working, and the base of the length measuring machine weighs more than 1 ton. It cannot be calibrated in situ. Likewise, on-site calibration cannot be achieved with non-portable devices.

Method 3: The paper "A New Device for Linear Displacement Sensor Calibration" was published in "Measurement Technology" Issue 05 in 2008; Authors: Han Qinghua, Wang Haiying. The grating ruler is used as the length standard.

This thesis is co-authored by myself, and it is a new device suitable for calibration in the measurement room environment. Its base adopts the base of the length measuring machine, which has the same shortcomings as the length measuring machine method.

Method 4: The paper "Application of Laser Interferometer in Calibrating Pull-Rope Displacement Sensors" was published in "Measurement and Testing Technology" Issue 03 in 2003; author: Li Deqian. The interferometer method is adopted, and the laser is used as the length standard. JJF1305-2011 "Linear Displacement Sensor Calibration Method", this method is generally used in the calibration of existing measurement rooms, and on-site calibration can be realized by designing corresponding fixtures.

The disadvantages of the interferometer method are:

1. The linear measurement accuracy of the interferometer is: ±0.5ppm (μm/m), and the on-site measurement environment and installation requirements are relatively strict, especially when working at heights, the erection and operation of the instrument are very difficult, and installation and adjustment are time-consuming and laborious. It is not economical to use such a high-precision standard for sensors with a linearity lower than 0.25%.

2. When calibrating, it must be equipped with a rotating mirror produced by the original interferometer to achieve on-site calibration. If the interferometer is not equipped with a rotating mirror (optional accessory), only horizontal and vertical sensor calibration can be carried out.

3. The laser beam emitted by the interferometer must always reach the target without obstruction. Once the laser beam is "broken", the calibration must start again.

Contents of the invention

The purpose of the present invention is to provide a method for on-site calibration of a linear displacement sensor, which is easy to install, accurate and quick to locate, and has universal applicability.

The technical solution of the present invention: a method for on-site calibration of a linear displacement sensor, characterized in that the method includes the following steps:

Step 1: Connect and fix the universal caliper with the linear displacement sensor, ensuring that the movement direction of the universal caliper is parallel to the movement direction of the linear displacement sensor;

Step 2, connecting and fixing the moving parts of the universal caliper with the moving parts of the linear displacement sensor;

Step 3, driven by the moving parts of the universal caliper, the moving parts of the linear displacement sensor move synchronously, read the standard displacement given by the universal caliper and the output value of the linear displacement sensor at each calibration point, and adjust the linear displacement according to the above data The sensor is calibrated.

Preferably, the universal caliper is a digital capacitance scale.

Preferably, the linearity of the linear displacement sensor is calibrated according to the following method:

Step 1, selecting a calibration point within the calibration range of the online displacement sensor;

Step 2, driven by the moving parts of the universal caliper, the moving parts of the linear displacement sensor move synchronously, read the standard displacement given by the universal caliper and the output value of the linear displacement sensor at each calibration point, until the upper limit of the calibration position is reached;

Step 3, perform reverse calibration in the same way as in step 2 until the lower limit of the calibration range is measured;

Step 4: establish the corresponding relationship between the standard displacement given by the universal caliper and the output value of the linear displacement sensor at each calibration point, and evaluate the linearity of the linear displacement sensor according to the corresponding relationship.

Preferably, the calibration range includes the actual working range of the linear displacement sensor, and the upper and lower limits each exceed 10% of the actual working range of the linear displacement sensor.

Preferably, the forward and reverse calibrations are 1 measurement cycle, and the linear displacement sensor linearity calibration includes at least 3 measurement cycles.

Preferably, the calibration points selected within the calibration range of the online displacement sensor include at least 6, including upper and lower limit position points.

Preferably, a calibration point is selected in the frequent working section of the sensor, and the forward and reverse directions of the calibration point are measured by means of mechanical limit, and the measurement result is recorded, and the return error calibration and evaluation of the linear displacement sensor is performed according to the measurement result.

Preferably, the backhaul error h _i is calculated according to the following formula:

In the formula: g _i ——the positive travel output of the sensor at the i-th calibration point,

b _i ——the reverse travel output of the sensor at the i-th calibration point,

Y _{FS ——The} difference between the sensor calibration upper limit output and the calibration lower limit output.

Preferably, a calibration point is selected in the frequent working section of the sensor, and the calibration point is repeatedly measured in one direction multiple times by means of mechanical limit, the measurement results are recorded, and the repeatability of the linear displacement sensor is evaluated according to the measurement results.

Preferably, the repeatability r _i of the linear displacement sensor is calculated according to the following formula:

In the formula: _Δi ——the difference between the maximum value and the minimum value of the output of the forward travel or reverse travel calibrated sensor at the same calibration point;

C——Range coefficient;

Y _{FS ——The} difference between the sensor calibration upper limit output and the calibration lower limit output.

Beneficial effects of the present invention: 1. The calibration equipment is different. The prior art adopts a gauge block, a laser interferometer, a length measuring machine and a displacement sensor calibration device, while the method adopts a capacitive digital display capacitive scale.

2. The measurement principle is different. The existing gauge block method is analog quantity comparison measurement; the laser interferometer method is the principle of interference distance measurement; the length measuring machine and the displacement sensor calibration device adopt the grating measurement principle. This method is the principle of capacitive ranging.

3. The calibration method is different. The existing method is not on-site calibration, but this method is on-site calibration, and the sensor does not need to be disassembled. The existing calibration methods do not combine the use factors, and all full-scale calibrations are used; this method considers the use factors and focuses on calibrating the use section. The existing method is to evaluate the repeatability of the measurement through three measurement results of a limited number of measurement points (10% of the full scale, including 11 calibration points at the beginning and the end), and the repeatability is performed simultaneously with other characteristic calibrations; this method is aimed at important work segments , Use frequent parts for enough measurements (more than 5 times). The method combined with engineering application is more scientific.

4. Alignment methods are different. The existing measuring block method is corrected by mechanical reference; the laser interferometer method is corrected by aiming at the target mirror through a rotating mirror; both the length measuring machine and the displacement sensor calibration device are corrected by the existing positioning device on the device. The method utilizes the shell of the sensor to cooperate with detection and fine-tuning to carry out alignment.

5. The data processing method is different. The existing method is to perform basic error, linearity, return error, and repeatability calibration at the same time. After three calibration calibration cycles (positive and negative are a calibration cycle) are completed, the calibration data is used to calculate the basic Error, linearity, return error, repeatability. The repeatability and return error are calculated from the 3-cycle data at the fixed calibration point (10% of the full scale, including 11 calibration points at the beginning and the end), which lacks pertinence. This method selects calibration points randomly or emphatically according to needs, and calculates the basic error and linearity through random measurement; repeats the repeated measurement of the frequently used parts and important parts for more than 5 times to evaluate the repeatability of the sensor, so that the static characteristics of the sensor can be evaluated. more realistic and reasonable.

Description of drawings

Fig. 1 schematic diagram of calibration method;

Figure 2 is a diagram of the positioning relationship between the reference block and the sensor;

Figure 3 is a diagram of the connection relationship between the universal caliper and the traction piece.

detailed description

The present invention will be described in detail below in conjunction with accompanying drawings and examples.

A calibration method. With reference to Fig. 1, it is characterized in that: use general-purpose caliper 2 as length standard device, connect and fix general-purpose caliper 2 and line displacement sensor 1, ensure that the movement direction of general-purpose caliper 2 is parallel to the movement direction of line displacement sensor 1. Connect and fix the moving parts of the universal caliper 2 and the moving parts of the linear displacement sensor 1. When the moving parts of the universal caliper 2 are driven by external force, the moving parts of the sensor 1 can move synchronously. From the digital display window of the universal caliper 2, read the standard displacement given by the universal caliper and the output values at each calibration point of the linear displacement sensor. Accuracy, return error, repeatability and other static characteristics are evaluated. The method comprises the steps of:

Step 1. Connect and fix the universal caliper with the linear displacement sensor to ensure that the movement direction of the universal caliper is parallel to the movement direction of the linear displacement sensor.

Referring to Figure 1, fit the lower surface of the ruler frame 5 of the universal caliper 2 whose size can cover the calibration range to the upper plane of the reference block 3 with a "V" groove, and use the pressure plate 4 and the measuring jaw 6 of the universal caliper 2 to The manufactured circular hole compresses the ruler frame 5 and fixes it on the reference block 3 .

Referring to Fig. 2, the strip "V" groove on the lower surface of the reference block 3 is straddled on the outer cylindrical surface of the sensor 1 to be calibrated along the axis of the sensor, and then through the four lugs 10 on the reference block 3, screw The connection method is to press and fix the universal caliper 2 and the sensor 1 on the test bench entity, use the lever dial indicator to "beat the meter" to measure, and use the tearable gasket to adjust and correct, and the inherent force inside the main ruler of the universal caliper 2 The reference side is parallel to the movement axis of sensor 1, and the included angle θ does not exceed ±0.002rad.

Step 2. Connect and fix the moving parts of the universal caliper with the moving parts of the linear displacement sensor.

Referring to Fig. 3, a traction member 9 is installed at the front end of the main ruler of the universal caliper 2, and acts on the leaf spring 8 by rotating the top screw 7, so that the traction member 9 embedded in the front end of the main ruler of the universal caliper 2 is fixed on the main ruler. Disconnect the moving part 14 of the sensor from the test drive system, so that the traction part 9 is reliably connected to the moving part 14 of the sensor to be calibrated.

Step 3. Calibration.

Driven by the moving parts of the general caliper, the moving parts of the linear displacement sensor move synchronously, read the standard displacement and the output value of the linear displacement sensor at each calibration point from the general caliper, and adjust the static state of the linear displacement sensor according to the above data characteristics are evaluated.

Step 3.1 Linearity Calibration. Calibrate the linearity of the linear displacement sensor according to the following method.

Step 3.1.1 Select calibration points within the calibration range of the online displacement sensor; select at least 6 calibration points within the calibration range of the online displacement sensor, including upper and lower limit position points. The calibration range includes the actual working range of the linear displacement sensor, and the upper and lower limits respectively exceed 10% of the actual working range of the linear displacement sensor.

Step 3.1.2 Driven by the moving parts of the universal caliper, the moving parts of the linear displacement sensor move synchronously, read the standard displacement given by the universal caliper and the output value of the linear displacement sensor at each calibration point, until the upper limit of the calibration range is reached ;

Step 3.1.3 is the same as the method in step 2. Carry out the reverse calibration until the lower limit of the calibration range measurement. The forward and reverse calibrations are 1 measurement cycle, and the linear displacement sensor calibration includes at least 3 measurement cycles.

Step 3.1.4 establishes the corresponding relationship between the standard displacement given by the universal caliper and the output value of the linear displacement sensor at each calibration point, and evaluates the linearity of the linear displacement sensor according to the corresponding relationship. The linearity is evaluated according to the least square method, endpoint method and reference straight line method.

Step 3.2 Backhaul error calibration.

Step 3.2.1 Determine the backhaul error calibration point. Within the 100mm working range where the sensor is frequently used, three locations are arbitrarily and uniformly selected as return error calibration points.

Step 3.2.2 Backhaul error calibration measurement. Take a forward and reverse measurement at each of the three calibration points. Record the measurements in three forward and reverse directions.

Step 3.2.3 Backhaul error data processing. Calculate the backhaul error h _i of the sensor to be calibrated according to the following formula.

In the formula: g _i ——the positive travel output of the sensor at the i-th calibration point;

b _i ——the reverse travel output of the sensor at the i-th calibration point;

Y _{FS ——The} difference between the sensor calibration upper limit output and the calibration lower limit output.

Step 3.3 Repeatability Calibration.

Step 3.3.1 Determine repeatability calibration points. Within the 100mm working range where the sensor is frequently used, randomly and evenly select three locations as repeatable calibration points.

Step 3.3.2 Repeatability Calibration Measurements. At the three calibration points, use mechanical limit methods such as positioning pins or limit blocks to perform repeated measurements in one direction for no less than 6 times, and record the results of 6 measurements in the same direction.

Step 3.3.3 Repetitive data processing. The repeatability error r _i is calculated according to the following formula.

In the formula: _Δi ——the difference between the maximum value and the minimum value of the output of the forward travel or reverse travel calibrated sensor at the same calibration point;

C——Range coefficient;

Y _{FS ——The} difference between the sensor calibration upper limit output and the calibration lower limit output.

Example

On-site calibration of the linear displacement sensor on the "Iron Bird" comprehensive test bench of a certain type of aircraft. A LVDT rod-type linear displacement sensor with a working range (0-100) mm installed on the wing of the test bench is selected to calibrate its linearity, return error, and repeatability. The solution and specific steps are as follows:

Referring to accompanying drawing 1, the main equipment of this method includes: sensor to be calibrated 1, digital display depth gauge 2, reference block with "V" groove 3, pressure plate 4, ruler frame 5, ruler claw 6, top wire 7, reed 8. Traction piece 9, lug piece 10, wire 11, digital multimeter 12, excitation power supply 13, measuring rod 14. The main measuring element is the digital depth gauge.

Solution and specific steps:

Step 1. Preparation before calibration.

Step 1.1 Determine the calibration range. According to actual needs, the actual working range of frequently used and important parts is determined to be (0-100) mm, and the calibration range is determined to be 120 mm, that is, the upper and lower limits of the calibration range exceed the actual working range by 10%.

Step 1.2 Under the premise of ensuring the coverage of the calibration range, connect and fix the digital display depth gauge 2 with the measurement range (0-200) mm to the linear displacement sensor 1 to ensure that the movement direction of the digital display depth gauge 2 is in line with the linear displacement sensor 1 The direction of motion is parallel. The specific method is as follows: see Figure 1, attach the lower surface of the ruler frame 5 of the digital display depth gauge to the upper plane of the reference block 3 with a "V" groove, use the pressure plate 4 and the base 6 of the digital display depth gauge The circular hole compresses the ruler frame 5 and fixes it on the reference block 3 . Referring to Figure 2, put the strip-shaped "V" groove on the lower surface of the reference block 3 on the outer surface of the cylinder of the sensor 1 to be calibrated along the axis of the sensor, and fix it with screws through the four lugs 10 on the reference block 3 Press and fix the digital depth gauge 2 and the sensor 1, use the lever dial indicator to "beat the meter" to measure, and use the tearable gasket to adjust and correct, and the inherent reference on the main scale of the digital display depth gauge 2 and the sensor 1 The axis of motion is parallel, and the angle θ between the horizontal and pitch directions does not exceed ±0.002rad.

Step 1.3 Refer to Figure 3, connect and fix the main ruler of the digital display depth gauge 2 with the measuring rod of the linear displacement sensor 1. The specific method is: install a traction piece 9 at the front end of the main ruler of the digital display depth gauge 2, and act on the reed 8 by rotating the top screw 7, and fix the traction piece 9 nested at the front end of the main scale of the digital display depth gauge 2 on the On the main scale, disconnect the measuring rod 14 of the sensor from the test drive system, so that the traction member 9 is reliably screwed to the measuring rod 14 of the sensor being calibrated.

Step 1.4 Manual test. Repeatedly push and pull the main ruler of the digital display depth gauge 2 within the calibrated range of 120 mm, adjust it to drive the sensor measuring rod 14 to move smoothly, and stop until there is no obvious mechanical block.

Step 1.5 Wiring. According to the definition of sensor wiring, the input terminal of the displacement sensor to be calibrated is correctly connected to the DC excitation power supply 13 through the wire 11; the output terminal is correctly connected to the digital multimeter 12. Check the wiring and circuit, and then turn on the +24V DC excitation after confirming that it is correct, so that the sensor is preheated for calibration.

Step 2. Calibration.

Step 2.1 Linearity Calibration.

Step 2.1.1 Determine linearity calibration points. Set the calibration points within the calibration range at 10% of the calibration range, including the upper and lower limits, and select 11 calibration points in total.

Step 2.1.2 Linearity Calibration Measurements. Driven by the main ruler of the digital display depth gauge 2, the measuring rod 14 of the linear displacement sensor 1 moves synchronously to move the sensor to the lower measurement limit along the current calibration direction. After adjusting the zero position of the sensor, reset the digital display depth gauge to zero. Calibration starts from the lower limit of measurement, according to the selected calibration points point by point to the upper limit of calibration, read out the linear displacement value L _i given by the digital display depth gauge and the electrical signal output value y _i of each calibration point in sequence. After the positive stroke reaches the upper limit of measurement, continue to move forward (1-10) mm to stop and return to the upper limit of measurement. Same as the forward stroke method, perform reverse calibration until the lower limit of measurement, record and establish a corresponding data list, see Table 1.

Table 1 Linear input and output correspondence list

Step 2.1.3 Linearity data processing. Using the least squares method, through 6 forward and reverse measurement data, the linearity of 6 single directions is evaluated as: -0.24%, -0.20%, -0.21%, -0.20%, -0.20%, - 0.21%, take -0.24% of the maximum absolute value as the linearity evaluation result of the sensor.

Step 2.2 Backhaul error calibration.

Step 2.2.1 Determine the backhaul error calibration point. Within the 100mm working range where the sensor is frequently used, three locations are arbitrarily and uniformly selected as return error calibration points.

Step 2.2.2 Backhaul error calibration measurement. Take a forward and reverse measurement at each of the three calibration points. Record the measurement results of three positive and negative directions, see Table 2.

Table 2 Correspondence list of backhaul input and output

Step 2.2.3 Backhaul error data processing. According to the following formula, the return error h _i of the sensor to be calibrated is calculated as 0.11%.

In the formula: g _i ——the positive travel output of the sensor at the i-th calibration point;

b _i ——the reverse travel output of the sensor at the i-th calibration point;

Y _{FS ——The} difference between the sensor calibration upper limit output and the calibration lower limit output.

Step 2.3 Repeatability Calibration.

Step 2.3.1 Determine repeatability calibration points. Within the 100mm working range where the sensor is frequently used, randomly and evenly select three positions as repeatable calibration points.

Step 2.3.2 Repeatability Calibration Measurements. At the three calibration points, by externally applying mechanical limits such as limit pins and positioning blocks, perform no less than 6 repeated measurements in one direction, and record the results of 6 measurements in the same direction, see Table 3.

Table 3 Repetitive input and output correspondence list

Step 2.2.3 Repeated data processing. Calculate the repeatability error r _i as 0.035% according to the following formula.

In the formula: _Δi ——the difference between the maximum value and the minimum value of the output of the forward travel or reverse travel calibrated sensor at the same calibration point;

C——Range coefficient;

Y _{FS ——The} difference between the sensor calibration upper limit output and the calibration lower limit output.

In order to verify the correctness of the method of the present invention, the sensor is disassembled and sent to a metrology laboratory for calibration, and the method of least squares and other methods listed in JJF1305-2011 "Linear Displacement Sensor Calibration Method" is used for evaluation. Results: Linearity: -0.22%; Return error: 0.11%; Repeatability: 0.033%. Through the comparison and analysis of the data of the method of the present invention under the measurement laboratory conditions, it is shown that the method is feasible.

Claims (10)

1. a kind of linear movement pick-up field calibration method, it is characterised in that described method comprises the following steps：

Step one, general calipers are connected with linear movement pick-up, it is ensured that the general calipers direction of motion is sensed with displacement of the lines The device direction of motion is parallel；

Step 2, the moving component of general calipers is connected with the moving component of linear movement pick-up；

Step 3, under the drive of general calipers moving component, the moving component of linear movement pick-up is synchronized with the movement, and reads general The linear movement pick-up output valve on standard displacement and each calibration point that slide calliper rule are given, and displacement of the lines is passed according to above-mentioned data Sensor is calibrated.

2. a kind of linear movement pick-up field calibration method according to claim 1, it is characterized by：Described general calipers It is digital display capacitive grating scale.

3. a kind of linear movement pick-up field calibration method according to claim 1, it is characterised in that according to following methods The linearity to linear movement pick-up is calibrated：

Step one, calibration point is chosen in linear movement pick-up calibration range；

Step 2, under the drive of general calipers moving component, the moving component of linear movement pick-up is synchronized with the movement, and reads general The linear movement pick-up output valve on standard displacement and each calibration point that slide calliper rule are given, until reaching the calibrating position upper limit；

Step 3, it is identical with step 2 method to carry out inverted order calibration, until calibration range measurement lower limit；

Step 4, the correspondence of the linear movement pick-up output valve set up on standard displacement and each calibration point that general calipers are given Relation, evaluates according to the corresponding relation to the linearity of linear movement pick-up.

4. a kind of linear movement pick-up field calibration method according to claim 3, it is characterized by：Described calibration range Including linear movement pick-up real work scope, bound is respectively more than the 10% of linear movement pick-up real work scope.

5. a kind of linear movement pick-up field calibration method according to claim 3, it is characterized by：Positive sequence and inverted order are calibrated It is 1 measurement circulation, described linear movement pick-up linearity calibration at least includes 3 measurement circulations.

6. a kind of linear movement pick-up field calibration method according to claim 3, it is characterized by：In linear movement pick-up The calibration point chosen in calibration range at least includes 6, location point containing bound.

7. a kind of linear movement pick-up field calibration method according to claim 1, it is characterized by：In the frequent work of sensor Make section and choose calibration point, by the way of mechanical position limitation, a positive and negative direction measurement is carried out to the calibration point, and record measurement As a result, the evaluation of hysterisis error school is carried out to linear movement pick-up according to the measurement result.

8. a kind of linear movement pick-up field calibration method according to claim 7, it is characterised in that according to below equation Calculate hysterisis error h_i：

$h_i=\frac{|g_i-b_i{|}_{max}}{Y_{FS}}\×100\%$

In formula：g_i--- sensor in i-th positive stroke output quantity of calibration point,

b_i--- sensor in i-th calibration point revesal output quantity,

Y_FS--- the difference of pick up calibration upper limit output quantity and calibration lower limit output quantity.

9. a kind of linear movement pick-up field calibration method according to claim 1, it is characterized by：In the frequent work of sensor Make section and choose calibration point, by the way of mechanical position limitation, multiple one direction duplicate measurements, record measurement knot are carried out to the calibration point Really, the repeatability of linear movement pick-up is evaluated according to the measurement result.

10. a kind of linear movement pick-up field calibration method according to claim 1, it is characterised in that according to below equation Repeatability to linear movement pick-up carries out calculating r_i：

$r_i=\frac{|{\mathrm{\Δ}}_i{|}_{max}}{C\·Y_{FS}}\×100\%$

In formula：Δ_i--- positive stroke or anti-row are by the difference of maxima and minima in the journey sensor output of school in same calibration point；

C --- extreme difference coefficient；

Y_FS--- the difference of pick up calibration upper limit output quantity and calibration lower limit output quantity.