EA034736B1 - Metrological stand for verification and calibration of level meters and level alarms - Google Patents

Abstract

The invention relates to measuring equipment and is intended for verification, calibration, graduation and other metrological tests of level meters and level alarms. A stand to check level gauges or level alarms, including a linear part with elements for connecting level indicators to be verified and a movable part, the linear part formed by metal profiles fixed to supports; in addition, the stand contains a reflector and means to move the reflector in a horizontal plane along the stationary linear part of the stand, while the calibrated level alarm or level gauge is installed in such a way that its horizontal axis is perpendicular to the plane of the reflector, characterized in that the instrument cabinet with a metal shield is rigidly fixed on the linear part to connect the level alarm or level gauge; and precision guide rails are mounted to move the rigid milled base on four precision trolleys along them; the movable part has a support frame rigidly fixed to it, its movement executed by a precision step drive using a reinforced toothed polyurethane belt, a reflector fixed on the support, the stand having a high-precision laser interferometer or laser range finder installed on an optical adjustable platform to measure the distance from the fixed metal shield to the movable reflector; the optical axis of the laser interferometer or laser range finder is set strictly perpendicular to the supporting frame, metal profiles are rigidly fixed to the adjustable supports, and a metering block is set on the stand to control ambient temperature, humidity and pressure.

Description

The invention relates to measuring equipment and is intended for verification, calibration, calibration and other metrological tests of level meters and level switches.

A well-known stand for adjustment and verification of radar level gauges (patent RU 2298770, IPC G01F 25/00, publ. 05/10/2007), which contains a stand made with the possibility of mounting the level gauge, support, a flat reflector mounted on a support, a horizontal movement device, made with the platform, a means of measuring the distance from the selected reference point to a flat reflector, an additional reflector and a screen of radar absorbing material. The support is placed on the platform of the horizontal movement device to change the distance (S) from the reference point (O) to the flat reflector. The screen is mounted on a means of horizontal movement thereof, made in the form of a cart rigidly connected by a connector to a horizontal movement device. An additional reflector is mounted on a stand and made in the form of a second-order surface. To reduce reflections from an additional reflector, two auxiliary screens are introduced in the form of curtains made of radar absorbing material.

A disadvantage of the known 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.

A known stand for the adjustment and calibration of radar level gauges (patent RU 2655750, IPC G01F 25/00, publ. May 29, 2018), which contains a rack for mounting the level gauge, a device for generating and processing signals, LET and antenna, support, a flat reflector located perpendicular to the straight line passing through the centers of the flat reflector and the aperture of the antenna, a horizontal displacement device, a distance measuring tool and a removable additional LETE from the LETE set with a discrete change in the electrodynamic length.

The disadvantage of this stand is the complexity of the design. A well-known stand has insufficient measurement accuracy in a wide range of ranges.

A known bench for checking level gauges (patent RU 140028, IPC G01F 25/00, publ. 04/27/2014), containing a fixed and moving part with bases fixed to each of them, a distance meter from the moving part to the fixed in the form of a measuring tape, means for reading the indicators of the meter, while on the basis of the fixed part the calibrated level gauge is rigidly fixed, and on the base of the movable part a reflector is fixed, and the calibrated level gauge is mounted so that its horizontal axis is perpendicular to the plane of reflection resident, there is a means for moving the reflector in a horizontal plane along the stationary linear part of the stand, equipped with elements for fixing it in a fixed state at predetermined points and including a movable part on which a base with a reflector is fixed, and guides for its movement in the form of aluminum profiles, fixed on supports and serving as a tool tray 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 meter readings. Taken as a prototype.

The disadvantage of the prototype is the necessary rigid constant monitoring of temperature parameters along the entire length of the stand; due to the location of the reference measuring ruler (along the guide, away from the measurement axis), the accuracy of the positioning of the moving part relative to the stationary decreases; 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 calibration, calibration, and sensor calibrations decreases.

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

EFFECT: increased accuracy of measuring the position of a supporting frame relative to a metal shield; reduction of measurement error to the required value; reduction of the total error of verification, calibration or calibration of level switches and level gauges.

The problem is solved, and the technical result is achieved by a stand for checking level gauges or level gauges, including a linear part with elements for connecting verified level gauges or level gauges and a moving part, while the linear part is presented in the form of metal profiles fixed to supports, in addition, the stand contains a reflector and means for moving the reflector in a horizontal plane along the stationary linear part of the stand, and the level indicator to be verified or the level gauge is set so in such a way that its horizontal axis is perpendicular to the plane of the reflector. In contrast to the prototype, the instrument cabinet with a metal shield is rigidly fixed on the linear part to connect a level switch or level gauge, and precision guide rails are mounted to move the rigid milled base with four precision trolleys, and on the moving part there is a rigid support frame, which is moved by precision stepper drive with a reinforced toothed polyurethane belt, and on which a reflector is fixed, and for measuring the distance from the fixed metal shield to the movable reflector, the stand contains a high-precision laser interferometer or laser range finder mounted on an optical adjustable platform, the optical axis of the laser interferometer or laser range finder is located strictly perpendicular to the supporting frame, and metal profiles are rigidly fixed to adjustable supports, moreover, a measuring unit was introduced into the stand to control temperature, humidity and ambient pressure.

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

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

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

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

used precision step drive SPSh20-34080;

To work with contact (capacitive) level gauges, the stand contains a cable of a contact (capacitive) level gauge, the tension of which is carried out using an electric winch with a tension sensor mounted on the pedestal.

The technical result is achieved as follows.

The support frame is moved using a precision step drive (in particular, SPSh20-34080), which ensures the accuracy of the support frame positioning with an accuracy of 0.1 mm when using a laser interferometer and 0.3 mm when using a laser range finder, in addition, the step drive provides fixed fixation of the supporting frame in a given position. To ensure the smooth running of the carrier frame and to prevent its movement in a fixed position, the movement is carried out using a reinforced toothed polyurethane belt.

The use of a laser interferometer or laser range finder, a precision stepper drive together with a reinforced toothed polyurethane belt, as a part of the stand, ensure the accuracy of the positioning of the support frame, rigid fixation in the given coordinate, followed by measuring the distance between the fixed metal shield and the support frame with an accuracy of 0.1 mm when using a laser interferometer and 0.3 mm when using a laser rangefinder; reduction of the total error of calibration, calibration or calibration of sensors or level sensors to a value of no worse than 0.3 mm when using a laser interferometer and 1 mm when using a laser range finder along the entire length of the stand.

The use of a laser interferometer, in addition, allows you to control the curvature of the path, and therefore the offset of the carrier frame relative to the axis of the sensor being verified in space, and to compensate for this offset by software; check the condition of the stand for straightness; adjust the straightness of the stand on the basis of the testimony of the interferometer and the adjustable bases of the linear part to the values necessary for verification, calibration and calibration of level switches and level gauges.

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

In FIG. 1 shows a functional diagram of the stand for working with ultrasonic and radar level gauges and level switches;

in FIG. 2 - functional diagram of the stand for working with contact (capacitive) level gauges and level switches.

In the drawings indicated

- the linear part of the stand,

- precision guide rails,

- a metal shield with universal mount for various sensors,

- supporting frame

- reflector

- rigid milled base,

- laser interferometer or laser range finder,

- optical adjustable platform,

- the optical axis of the measurement of the interferometer or laser range finder,

- linear retroreflector,

- verifiable level gauge or level indicator,

- instrument cabinet

- reinforced toothed polyurethane belt,

- precision stepper drive,

- a stand by means of which a laser interferometer is fixed to the floor,

- an electric winch with a tension sensor,

- the stand on which the winch is mounted,

- precision trolleys,

- 2 034736

- measuring unit,

- reference sensor

- 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 horizontal and vertical planes. The location of the reflective surface is determined by determining the location of the supporting frame 4 relative to the fixed metal shield 3 using a laser interferometer or laser range finder 7. On the linear part 1, precision guide rails 2 are mounted, along which a rigid milled base 6 is moved using four precision trolleys 18, which, in turn, mounted all mobile equipment. A verifiable level switch or level gauge 11 is firmly fixed to the metal shield 3; a reflector 5 is mounted on the carrier frame 4 of the movable part, and the level indicator to be calibrated and the level gauge 11 are mounted so that its horizontal axis is perpendicular to the plane of the reflector 5. The carrier frame 4 is designed to move the reflector 5 in a 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 range finder 7 mounted on an optical adjustable platform 8. The optical axis 9 is located strictly perpendicular to the supporting frame 4 and reflector 5.

To compensate for the drift of measurements from changes in temperature, pressure and humidity, a measuring unit 19 was introduced into the composition of the stand for monitoring temperature, humidity and ambient pressure.

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

The support frame 4 is moved using a precision stepper drive (in particular, SPSh20-34080) 14, which ensures the accuracy of the support of the support frame 4 with an accuracy of 0.1 mm when using a laser interferometer and 0.3 mm when using a laser rangefinder, in addition, a stepper drive provides a fixed fixation of the carrier frame in a given position.

To ensure smooth running of the supporting frame 4 and to prevent 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 level unit is based on the movement of the reflective surface along the stationary linear part 1 of the stand at a given distance.

Verification is as follows.

A calibrated level switch or level gauge 11 is rigidly mounted in a horizontal position on a fixed 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 level indicator or level gauge to be verified, the calibration / verification process begins in accordance with the calibration procedure for this sensor. The next step is to supply power to the stand, to the level switch or level gauge and configure the parameter of the recorded signal. After start-up, an automatic interrogation of all connected interfaces takes place (a precision stepper drive, a laser interferometer or a laser range finder, a signal from a level indicator or level gauge being verified, through an interface module), and temperature, pressure, and humidity parameters are checked.

In the case of using a laser interferometer 7, it is rigidly fixed to the floor through an optical adjustable platform 8 by means of a pedestal 15, the pedestal 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 supporting frame 4 for operation with the interferometer. In the case of using a laser interferometer, it is necessary to perform initial calibration of the stand to determine the absolute spatial position of the reflector 5 (performed using a reference sensor 20, which calibrates the distance between the metal shield 3 and frame 4 with an accuracy of no worse than 0.1 mm). Next, the operator selects the type of level switch or level gauge (non-contact, contact), sets the range of level measurements (according to the passport data), and, based on the verification methodology, assigns the number of passes and points (coordinates) by which the verification takes place. The positioning of the reflector 5 in a given coordinate is carried out using a precision stepper drive and according to data from a laser interferometer with a total error of not more than 0.3 mm. This absolute value is compared with the readings of the level switch and is entered in the automatically generated protocol. On the basis of the verification protocol and passport data, a conclusion on the suitability for use is made to the level switch.

The use of a laser interferometer allows one to achieve verification accuracy (total error

- 3 034736), calibration and calibration of the stand to values not more than 0.3 mm over the entire length.

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

2. To control the curvature of the path, and therefore the displacement of the carrier frame relative to the axis of the level indicator or level gauge in space to be verified, and to compensate for this displacement using software.

3. Check the status of the stand for straightness.

4. To adjust the straightness of the stand on the basis of the readings of the laser interferometer and the adjustable bases of the linear part to the values necessary for verification, calibration and calibration of level meters 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 (signaling device) or level gauge allows to reduce the measurement error to the required value.

6. The accuracy of verification, calibration or calibration of level gauges or level switches to a value not worse than 0.3 mm over the entire length.

Depending on the characteristics of level switches or level meters (measurement errors) and the accuracy requirements of the bench, a laser rangefinder can be used instead of a laser interferometer. At the same time, the accuracy of verification (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, primary calibration of the stand to determine the absolute spatial position of the reflector 5 is not required. After polling all devices and interfaces, the operator immediately proceeds to the choice of the type of level switch and level gauge, the task of the measurement range, assigns the number of passes and points (coordinates) by which calibration is performed. The positioning of the reflector 5 in a given coordinate occurs using a precision step drive and according to the data from the laser range finder with a total error of not more than 1 mm. This absolute value is compared with the readings of the level switch or level gauge and is entered in the automatically generated protocol. On the basis of the verification protocol and passport data, a conclusion on suitability for use is made to the level switch or level gauge.

The use of a laser rangefinder allows

1) economically more profitable application,

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

3) 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 using the reference sensor 20,

4) ease of calculation of the result using software,

5) the accuracy of verification, calibration or calibration of level gauges or level switches to a value not worse than 1 mm over the entire length,

6) the lack of strict requirements for monitoring climate parameters.

Claims (7)

1. A stand for checking level gauges or level indicators, including a linear part with elements for connecting verified level indicators and a moving part, the linear part being presented in the form of metal profiles fixed to 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 level indicator to be verified or the level gauge is installed so that its horizontal axis is perpendicular to the plane of reflection atelier, characterized in that the instrument cabinet with a metal shield is rigidly fixed on the linear part to connect a level indicator or level gauge, and precision guide rails are mounted to move the rigid milled base by means of four precision trolleys, and on the movable part is a support frame, the movement of which is carried out by means of a precision stepper drive using a reinforced toothed polyurethane belt, and on which a reflector is fixed, to measure the distance from the fixed metal shield to the movable reflector, the stand contains a high-precision laser interferometer or laser range finder mounted on an optical adjustable platform, while the optical axis of the laser interferometer or laser range finder is located strictly perpendicular to the supporting frame, and metal profiles are rigidly fixed to adjustable supports, and The measuring unit for monitoring temperature, humidity and ambient pressure was introduced into the stand. 2. The stand according to claim 1, characterized in that when using a laser interferometer on the precision guide rails of the linear part, a reference sensor is installed to determine the reference point. - 4 034736 3. The stand according to claim 1, characterized in that when using a laser interferometer, a linear retroreflector is mounted on the supporting 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 that is not connected with the main frame of the stand. 5. The stand according to claim 1, characterized in that the measuring unit is equipped with temperature sensors, pressure and humidity sensors. 6. The stand according to claim 1, characterized in that the precision stepper drive SPSh20-34080 is used as part of a reinforced polyurethane drive belt. 7. The stand according to claim 1, characterized in that for working with contact cable (capacitive) level gauges, the stand uses a tension system, which is carried out using an electric winch with a tension sensor mounted on the pedestal.