The output of the pressure transmitter cannot be zeroed
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Shanghai Automation Instrument Co., Ltd. 3151 GP pressure transmitter: Under normal pressure conditions, the transmitter displays 0 Mpa and 4 mA, but when a ammeter is used to measure the output current, it reads 5.89 mA. When using a domestic 475 HART device for adjustment of the \"4 mA output\", it is not possible to get the output current to 4 mA. What’s going on here? For loop testing, it can output normally.
475: Call calibration to set the current pressure to zero and give it a try
The output power amplifier module is broken. The internal processing of such transmitters is digital; only the final current output involves a digital-to-analog conversion. The handheld controller does not work with analog circuits.
Check if the range has been modified
The pressure reading is zero, and the current output does not reach 4mA.
Is there a calibration lock? I remember that Honeywell watches have one; there’s a small pin behind the dial – you can take a look.
This situation is definitely due to a problem with the circuit board conversion; it’s not necessarily an issue with the mA output – it’s possible that the linearity has also changed. Take out the circuit board and try replacing it to confirm.