RU2690701C2 - Metrological bench for verification, calibration of level gauges and level indicators - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention is intended for verification, calibration, calibration and other metrological tests of level gauges and level indicators. Test bench includes a linear part and a movable part, as well as a reflector and means for moving the reflector. At that, on linear part is rigidly fixed instrument table with metal shield for connection of level indicator or level gauge, as well as precision guide rails for moving rigid milled base by means of four precision trolleys. On the movable part the bearing frame is rigidly fixed, movement of which is carried out by means of the precision step drive by means of the reinforced toothed polyurethane belt, and on which the reflector is fixed. At that, for measurement of distance from fixed metal shield to moved reflector stand contains high-precision laser interferometer or laser range finder installed on optical adjustable platform. Besides, test bench incorporates measuring unit to control temperature, humidity and ambient pressure.

EFFECT: reducing calibration, calibration and calibration errors of level and level gauges.

7 cl, 2 dwg

Description

The invention relates to measuring equipment and is intended for calibration, calibration, calibration and other metrological tests of level gauges and level alarms.

Known stand adjustment and calibration of radar level gauges (patent RU2298770, IPC G01F 25/00, publ. 10.05.2007), which contains a rack configured to mount the level gauge, a support, a flat reflector mounted on a support, a horizontal movement device made with a platform, a means of measuring the distance from the selected reference point to a flat reflector, an additional reflector and a screen made of radio absorbing material. The support is placed on the platform of the device for horizontal movement to change the distance (S) from the origin (O) to the flat reflector. The screen is installed on the means of horizontal movement, made in the form of a trolley rigidly connected by a connector with a device for horizontal movement. An additional reflector is mounted on a rack and made in the form of a surface of the second order. To reduce reflections from the additional reflector, two auxiliary screens are introduced in the form of curtains of radio absorbing material.

The disadvantage of this stand is the complexity of the design, due to the presence of an additional reflector and several screens, low accuracy of determining the distance to the plane of the reflector.

Known stand adjustment and calibration of radar level gauges (patent RU2655750, IPC G01F 25/00, publ. 05/29/2018), which contains a rack for mounting the level gauge, a device forming and processing signals, LEEE and antenna, a support, a flat reflector located perpendicularly a straight line passing through the centers of a flat reflector and an aperture of the antenna, a horizontal displacement device, a means of measuring the distance and a removable additional LEEE from the LEEE set with a discrete variation of the electrodynamic length.

The disadvantage of the famous stand is the complexity of the design. The famous stand has insufficient measurement accuracy in a wide range of ranges.

A stand for calibration of gauges is known (patent RU140028, IPC G01F 25/00, publ. 04/27/2014), containing fixed and movable parts with bases fixed on each of them, a distance meter from the movable part to the fixed one in the form of a measuring tape, means readings of indicators of the meter, while on the basis of the fixed part a calibrated level gauge is rigidly fixed, and a reflector is fixed on the basis of the movable part, and the calibrated level gauge is installed so that its horizontal axis is perpendicular to the plane of the reflector there is a means for moving the reflector in a horizontal plane along the fixed linear part of the stand, equipped with fixing elements in a stationary state at specified points and including a movable part on which the base with a reflector is fixed, and guides for moving it in the form of aluminum profiles, mounted on supports and serving as a lodgement for laying the measuring tape, the tension of which is provided by the load. The stand is equipped with temperature sensors, a position sensor is located at the base of the fixed part of the stand, and a linear encoder is used as a means of reading the indicators. Taken as a prototype.

The disadvantage of the prototype is the necessary hard constant monitoring of temperature parameters along the entire length of the stand; because of the location of the reference measuring ruler (along the guide, away from the axis of measurement), the positioning accuracy of the moving part relative to the fixed part decreases; the strong dependence of distance measurement on the curvature of the guides; The error in measuring the distance depending on the curvature of the second guide, which does not have a magnetic ruler, as a result of which the accuracy of calibrations, graduations, and calibrations of sensors decreases.

The objective of the invention is to reduce the error of calibration, calibration and calibration of level switches and level gauges.

The technical result is a reduction in the total error of calibration, calibration or calibration of level alarms and level gauges; reduction of measurement error to the required value; improving the accuracy of measuring the position of the carrier frame relative to the metal shield.

The problem is solved, and the technical result is achieved by a bench for calibration of level gauges or level alarms, including a linear part with elements for connecting verifiable level alarms and a movable part, while the linear part is presented in the form of metal profiles fixed on supports, in addition, the stand contains a reflector and Means for moving the reflector in the horizontal plane along the fixed linear part of the stand, and the calibrated level indicator or level gauge is installed in such a way that Its horizontal axis is perpendicular to the plane of the reflector. Unlike the prototype, the instrument panel with a metal shield for connecting a level indicator or a level gauge is rigidly fixed on the linear part, and precision guide rails are mounted to move the hard milled base by means of four precision carts, and the supporting frame is rigidly fixed to the movable part, precision stepper drive using a reinforced toothed polyurethane belt, and which is fixed to the reflector, and for Measuring the distance from a fixed metal shield to a movable reflector, the stand contains a high-precision laser interferometer or laser rangefinder mounted on an adjustable optical platform, while the optical axis of the laser interferometer or laser rangefinder is located strictly perpendicular to the carrier frame, and the metal profiles are fixed on adjustable supports, and the composition of the stand introduced a measuring unit to monitor the temperature, humidity and pressure of the environment.

According to the invention:

- when using a laser interferometer on the precision guide rails of the linear part, a reference sensor is installed to determine the point of reference;

- when using a laser interferometer, a linear retroreflector is fixed on the carrier frame;

- the laser interferometer is fixed through the optical adjustable platform to the floor by means of a pedestal, not connected with the main frame of the stand;

- the stand is equipped with temperature sensors, pressure and humidity sensors;

- used precision stepper drive SPSh20-34080 in the composition with a reinforced polyurethane drive belt;

- for work with contact wire (capacitive) level gauges, the stand contains a tension system, including an electric winch with a tension sensor, mounted on a pedestal.

The technical result is achieved as follows. The carrier frame is moved using a precision stepper drive (in particular, SSP20-34080), which ensures the positioning accuracy of the carrier frame with an accuracy of 0.1 mm when using a laser interferometer and 0.3 mm when using a laser rangefinder, in addition, the stepping drive provides a fixed fixation carrier frame in a given position. To ensure the smoothness of the carrier frame and eliminate its movement in a fixed position, the movement is carried out using a reinforced toothed polyurethane belt.

The use of a laser interferometer or a laser rangefinder stand, a precision stepper drive together with a reinforced polyurethane belt provide positioning accuracy of the carrier frame, rigid fixation at a given coordinate, followed by measuring the distance between the fixed metal shield and the carrier frame with an accuracy of 0.1 mm when using a laser interferometer and 0.3mm using a laser rangefinder; reduction of the total error of calibration, calibration or calibration of sensors or level detectors to a value not less than 0.3 mm when using a laser interferometer, and 1 mm when using a laser rangefinder over the entire length of the stand.

The use of a laser interferometer, in addition, allows you to control the curvature of the path, and, consequently, the displacement of the carrier frame relative to the axis of the sensor being calibrated in space and compensate for this displacement with the help of programs of means; check the condition of the stand for straightness; adjust the straightness of the bench on the basis of the interferometer readings and adjustable bases of the linear part, up to the values required for calibration, calibration and calibration of level alarms and level gauges.

The use of a laser rangefinder allows, in addition, to produce a more simple calculation of the result using software.

Figure 1 - shows the functional diagram of the stand for working with ultrasonic and radar level gauges and level switches;

Figure 2 - shows the functional diagram of the stand for working with cable contact (capacitive) level gauges and level switches.

In the figures indicated:

1 - linear part of the stand

2 - precision guide rails

3 - metal shield with universal mount for various sensors

4 - bearing frame

5 - reflector

6 - hard milled base

7 - laser interferometer or laser rangefinder

8 - optical adjustable platform

9 - optical axis of measurement of an interferometer or laser rangefinder

10 - linear retroreflector

11 - calibrated level gauge or level alarm

12 - dresser instrument

13 - reinforced toothed polyurethane belt

14 - precision stepper drive

15 - bollard, through which the laser interferometer is fixed to the floor

16 - electric winch with a tension sensor

17 - pedestal on which the winch is installed

18 - precision carts

19 - measuring unit

20 - reference sensor

21 - cable contact (capacitive) level gauge.

The inventive stand works as follows.

       The linear part of the stand 1 is presented in the form of metal profiles fixed on rigidly fixed adjustable supports ensuring their installation and adjustment in the horizontal and vertical planes. The location of the reflective surface is determined by determining the location of the carrier frame 4 relative to the fixed metal shield 3 using a laser interferometer or laser rangefinder 7. On the linear part 1, precision guide rails 2 are mounted, along which a rigid milled base 6 is moved using four precision carriages 18, to which, in turn, mounted all mobile equipment. A calibrated level indicator or level gauge 11 is firmly fixed on the metal shield 3; The reflector 5 is fixed on the carrier frame 4 of the movable part, and the calibrated level indicator and the level gauge 11 are installed so that its horizontal axis is perpendicular to the plane of the reflector 5. The base frame 4 is designed to move the reflector 5 in the horizontal plane along the rails 2.

The distance from the fixed metal shield 3 to the movable reflector 5 is measured using a high-precision laser interferometer or laser rangefinder 7 mounted on an adjustable optical platform 8. The optical axis 9 is located strictly perpendicular to the carrier frame 4 and the reflector 5.

To compensate for the drift of measurements from changes in temperature, pressure and humidity, a measuring unit 19 was introduced into the bench to control the temperature, humidity and pressure of the environment.

The stationary metal shield 3 has a universal fastening system (milled metal plate 16 mm thick with universal mortgages) for installing various types of level gauges.

Moving the carrier frame 4 is carried out using a precision stepper drive (in particular, SSP20-34080) 14, which ensures the positioning accuracy of the carrier frame 4 with an accuracy of 0.1 mm when using a laser interferometer and 0.3 mm when using a laser rangefinder, moreover, stepper drive provides a fixed fixation of the carrier frame in a given position.

To ensure smooth running of the carrier frame 4 and eliminate its movement in a fixed position, the movement is carried out using a reinforced toothed polyurethane belt.

The principle of simulating the reproduction of a unit of level is based on the movement of a reflective surface along a fixed linear part 1 of a stand for a specified distance.

Verification is as follows.

A calibrated level indicator or level gauge 11 is rigidly fixed in a horizontal position on a stationary metal shield 3. The sensor is installed in such a way that the plane of the metal shield 3 is parallel and its horizontal axis is perpendicular to the plane of the reflector 5.

After installing the calibrated level gauges or level gauge, the process of calibration / verification begins in accordance with the method of calibration for this sensor. The next step is to energize the stand, the level indicator or level gauge and set the parameter of the signal to be removed. After start-up, all interconnected interfaces are automatically polled (precision stepper drive, laser interferometer or laser range finder, signal from a calibrated level indicator or level gauge, via an interface module), checking parameters of temperature, pressure, humidity.

In the case of using a laser interferometer 7, it is rigidly fixed to the floor through a stand 15 through an optical adjustable platform 8, the stand is untied from the main frame of the stand. In addition, for the operation of the laser interferometer 7, a linear retroreflector 10 is installed on the carrier frame 4 for operation with the interferometer. In the case of a laser interferometer, it is necessary to perform a primary calibration of the test bench to determine the absolute spatial position of the reflector 5 (made using a reference sensor 20, which calibrates the distance between the metal shield 3 and frame 4 with an accuracy not worse than 0.1 mm.). Next, the operator selects the type of level indicator or level gauge (contactless, contact), sets the level measurement range (according to the passport data), based on the calibration method, assigns the number of passes and points (coordinates) for which the calibration takes place. The positioning of the reflector 5 in a given coordinate occurs using a precision stepper drive and, according to data from a laser interferometer, with a total error of less than 0.3 mm. This absolute value is compared with the readings of the level indicator and entered into an automatically generated protocol. On the basis of the verification protocol and passport data, a conclusion is made on the level indicator about suitability for use.

The use of a laser interferometer allows you to achieve the accuracy of calibration (total error), calibration and calibration of the stand to values not more than 0.3 mm over the entire length:

1. To improve the accuracy of measuring the position of the carrier frame relative to the metal shield 3 with an accuracy not worse than 0.1 mm.

2. Control the curvature of the track, and, consequently, the displacement of the carrier frame relative to the axis of the calibrated level indicator or level gauge in space and compensate for this displacement with the help of programs of means.

3. Check the condition of the stand for straightness.

4. Adjust the straightness of the stand on the basis of the readings of the laser interferometer and the adjustable bases of the linear part, up to the values necessary for verification, calibration and calibration of level gauges and level alarms.

5. The location of the axis of the laser interferometer in close proximity to the axis of the calibrated (calibrated) level sensor (indicator) or level gauge allows reducing the measurement error to the required value.

6. Accuracy of verification, calibration or calibration of level gauges or level alarms up to a value not worse than 0.3 mm over the entire length.

Depending on the characteristics of level sensors or level gauges (measurement errors) and the accuracy requirements of the test bench, a laser rangefinder can be used instead of a laser interferometer. At the same time, the accuracy of calibration (total error), calibration and calibration of the stand is reduced to 1 mm over the entire length.

In the case of using a laser rangefinder, a primary calibration of the test bench is not required to determine the absolute spatial position of the reflector 5. After interrogating all devices and interfaces, the operator immediately proceeds to select the type of level indicator and level gauge, the task of the measurement range, assigns the number of passes and points (coordinates) by which the verification takes place. The positioning of the reflector 5 in a given coordinate occurs using a precision stepper drive and, according to data from a laser rangefinder, with a total error of less than 1 mm. This absolute value compares with the readings of the level indicator or level gauge and is entered into the automatically generated protocol. On the basis of the verification protocol and passport data, the level indicator or level gauge is concluded on suitability for use.

The use of a laser rangefinder allows you to:

1. Cost-effective use.

2. The location of the axis of the laser rangefinder in close proximity to the axis of the calibrated (calibrated) level gauge, level indicator allows you to reduce the measurement error to the required value.

3. The simplicity of the stand. In particular, there is no need to calibrate the distance between the fixed metal shield 3 and the movable frame 4 with the help of the reference sensor 20.

4. Ease of result calculation using software.

5. Accuracy of calibration, calibration or calibration of level gauges, or level gauges to a value no worse than 1 mm over the entire length.

6. The absence of strict requirements for the control of climatic parameters.

Claims (7)

1. Stand for calibration of level gauges or level alarms, including a linear part with elements for connecting calibrated level alarms and a movable part, while the linear part is presented in the form of metal profiles fixed on supports, in addition, the stand contains a reflector and means for moving the reflector in horizontal plane along the stationary linear part of the stand, and the calibrated level indicator or level gauge is installed so that its horizontal axis is perpendicular to the plane of A linear instrument cluster with a metal shield for connecting a level indicator or a level gauge is fixed on the linear part, and precision guide rails are mounted to move the rigid milled base by means of four precision carriages, and the supporting frame is rigidly fixed on the movable part carried out by means of a precision stepper drive using a reinforced toothed polyurethane belt, and on which a reflector is fixed, with To measure the distance from a fixed metal shield to a movable reflector, the stand contains a high-precision laser interferometer or laser rangefinder mounted on an adjustable optical platform, while the optical axis of the laser interferometer or laser rangefinder is located strictly perpendicular to the carrier frame and the metal profiles are fixed on adjustable supports, and A measuring unit was introduced into the stand to monitor the temperature, humidity and pressure of the environment. 2. The stand according to claim 1, characterized in that when using a laser interferometer on a precision guide rails of the linear part, a reference sensor is installed to determine the point of reference. 3. Stand according to claim 1, characterized in that when using a laser interferometer, a linear retroreflector is attached to the carrier frame. 4. The stand according to claim 1, characterized in that the laser interferometer through an optical adjustable platform is rigidly fixed to the floor by means of a pedestal, not connected with the main frame of the stand. 5. The stand according to claim 1, characterized in that the stand is equipped with temperature sensors, pressure sensors and humidity. 6. The stand according to claim 1, characterized in that used precision stepping drive SPS20-34080 in the composition with a reinforced polyurethane drive belt. 7. Stand according to claim 1, characterized in that for working with contact cable (capacitance) level gauges, the stand contains a tension system, including an electric winch with a tension sensor, mounted on the base.

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