Why does the range change after I calibrate the output current of the pressure transmitter? ?
Thread Content
Our company has a pressure transmitter with a range of (0-10) MPa. When it was calibrated using a pressure testing bench, it was found that the current output differed significantly from the actual pressure value. After calibrating it at 4 mA and 20 mA, it was observed that the range of the pressure transmitter changed automatically (the range became 0-9.6 MPa). What is the reason for this?
Either the range is originally 0-9.6 MPa, not 10 MPa. Either the meter has gone crazy, and you’ve encountered a ghost................................ Encountering a ghost is such a rare thing – was it a female ghost? If so, go ahead and fiddle around a bit; create a bunch of Hart tables and bring about a miracle in the process. :lol
Line interference, line losses, instrument drift – identify the causes and take appropriate actions
There might be a problem with the digital-to-analog conversion-amplifier circuit. For many smart meters, the analog output is generated after digital processing, with a separate analog-to-digital conversion-amplifier circuit responsible for producing the analog signal. When there is a problem with this circuit, the analog output will not match the Hart standards; even after calibration based on analog values, the zero point and range of the Hart signal will still not be in line with the specified values. Problems with the digital-to-analog conversion-amplifier circuit: 1. The output analog value does not match the digital value ； 2. The deviation between the output analog and digital values increases as the resistance of the output circuit increases. The main reason for the discrepancy between analog and digital values is the aging of the power amplifier circuit; the power supplied by the 4-20mA signal is not sufficient to meet the circuit’s power requirements.