Differential air pressure transmitter measurement verification problems
Differential air pressure transmitters often choose to perform metrological verification in the laboratory. In fact, the differential air pressure transmitter plays a decisive role in industrial control and has a wide range of applications. It is inevitable to use it under high temperature, high pressure, electromagnetic interference, and mechanical vibration. Some pressure transmitting media are even highly corrosive or Heavy viscosity, on-site environment is very complex, plus the installation location, use and maintenance, different personnel, measurement disputes occur from time to time, to the majority of business users and measurement workers bring a lot of trouble, how to improve the differential pressure transmitter measurement results are objective Fairness has become a problem to be solved in metrological verification. Here are some aspects that are easily overlooked and worth noting in our metrological verification.
Differential Air Pressure Transmitters Metrology Verification Points to Note Problems Differential Air Pressure Transmitters
1. According to the range of the differential pressure transmitter to be tested, select the air pressure transmitting medium, and measure the upper limit value of the transmitter which is not greater than 0,25 MPa. The pressure transmission medium is air or other non-toxic and harmless, the chemical performance is stable, and it is clean and dry. Transmitters for gases and measuring upper limit values greater than 0.25 MPa are generally liquid, so use liquids recommended by the manufacturer or specified by the submitter.
2. According to the measuring range and precision of the differential air pressure transmitter, select standard instruments and related equipment. The extended standard 2088 introduced by the standard device after complete set does not exceed the absolute value of the maximum allowable error of the transmitter. /4, For 0.1 and 0.05 tested transmitters, the 2088 introduced here shall not exceed 1/3 of the absolute value of the maximum allowable error of the transmitter.
3. If the condition of the tested transmitter is using a medium containing dust, grease, and micro-particles, the pressure transmitter should be drained prior to the test, and the drain on the transmitter body should be turned on (exhaust). ) Screws or valves that pressurize the transmitter to remove fluid and dirt from the transmitter cavity are located in the standard unit. When the sewage is discharged, a container shall be placed under the sewage valve. It is the dirt in the pressure chamber that enters the container to prevent the pollution of the environment.
4. Equipment connection and installation, pressure calibration station first level adjustment. The standard pressure signal and transmitter are installed on the signal tube. There should be gaskets at the interface. The tightness of the top and bottom compression bolts should be the same to prevent leakage and make the transmitter at the same level as the pressure reference plane of the pressure standard module. Location. Connect the calibration circuit, check whether the standard module, measurement unit, and signal output are correct. Then, fill the entire device with oil and exhaust gas so that the pressure-transmitting tube is filled with pressure-transmitting medium and slowly pressurize the upper limit of the measurement. Stay for a few minutes and observe no leakage. In addition, in order to prevent the hysteresis of the pressure change caused by the damping time, the transmitter's damping value is adjusted to zero before the verification.