The Issues in the Application of the Calibration of the DP Transmitter

The Issues in the Application of the Calibration of the DP Transmitter

DP Transmitter are widely used in many enterprises, such as chemical industry, metallurgy, light industry, etc., most of which are used to measure pressure, level, flow and other parameters. The calibration of DP Transmitter is a practical task. Very common job. The following puts forward some thoughts on the verification of DP Transmitter in the specific operation of several problems.

1 Problems with the verification procedures for the use of DP Transmitter

There is no corresponding metrological verification standard in the national standard for the calibration of the differential pressure transmitter. At present, the metrological verification standard we can adopt is JJG882-2004 Excitation Transmitter Verification Regulation. This regulation is for pressure transmitters, not specifically for DP Transmitter. The differential pressure transmitter measures the difference between two pressure values. According to the current basic calibration, the current calibration of the other pressure is mainly to directly connect to the atmosphere and use the natural atmospheric pressure for calibration.

2 Differential pressure transmitter verification types

According to the measurement and verification standards of pressure transmitters, there are three types of verifications for pressure transmitters: first verification, subsequent verification, and in-use verification. The content of the three kinds of verifications is different according to the measurement standards. In practice, the problem here is the measurement of insulation resistance. According to the requirements of the standard, the follow-up verification and use are tested, of which the follow-up test needs to measure the insulation resistance. The measurement requirement is to use a DC 500V insulation resistance meter (capacitive differential pressure transmitter uses a 100V insulation resistance meter) to measure under the requirements, and the insulation resistance is not less than 20MQ. However, in practice, the insulation resistance of the transmitter is rarely measured. The reason is that the insulation requirements are very high. If the basic factory verification is qualified, there will be no problems in the follow-up; secondly, the current differential pressure transmitter is basically It is a two-wire system and uses a DC 24V voltage. This voltage basically has no safety problems. It can only be used to protect the instrument from external overvoltages and is very measured in the follow-up verification.