What is the purpose of testing the EJA differential pressure level transmitter circuit?
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I’m seeking help from experts. Today, the EJA differential pressure level gauge is showing inaccurate readings with significant fluctuations. The transmitter passed its self-check, and out of curiosity I ran a loop test using the handheld controller; it seemed to be a 4mA loop test. I’m not sure whether a level gauge can even undergo such a loop test. After running the test, the reading kept showing negative values – I don’t know why. What is the purpose of the loop test in the diagnostic functions? Does any expert know?
The loop test should involve having the transmitter output a specified value, and then comparing that value with the value displayed on the DCS to determine whether the loop is functioning properly
Given a fixed current signal, check whether this fixed value changes after passing through the instrument’s analog output module. After that, it is necessary to exit properly for the instrument to return to normal; otherwise, it will remain in test mode. Or the instrument needs to be powered off in order to return to normal
Loop testing is of two types: one is used to check whether the transmitter’s loop is functioning properly, that is, whether the received current signal can accurately reflect the corresponding liquid level. The second is to test whether the communication between the instrument and the control system is functioning properly. Generally, using a handheld operator to exit the loop test will allow the transmitter to return to normal operating mode. If the display shows abnormal and severe fluctuations, it is recommended that you use a signal generator to supply a signal to the transmitter separately, or put the control room in test mode and switch to operating mode to see if the fluctuations still occur If the skip condition no longer appears and everything shows normal, then it’s possible that the fluctuations in the level gauge are due to process-related reasons. If a negative value is displayed continuously after operation, it may be because, once the control system is disabled, the transmitter shows the actual value; in other words, the diaphragm may have deformed, and it needs to be zeroed out again.