When the pressure reading on the PLC or SCADA does not agree with the pressure gauge, it must be determined whether there is an actual pressure deviation or a measurement problem.
Comparison with an independent instrument
The pressure is verified with a reliable reference instrument at the same or a very close point.
Zero and span check
The transmitter may have a zero shift or an incorrect calibration range.
Impulse line
A clogged, kinked, or condensate-filled impulse line can give a false reading.
4–20 mA
It is checked whether the output current corresponds to the physical pressure and if the scaling in the PLC is correct.
Intermittent fault
Loose connections, electrical noise, or a power supply problem can create spikes or dips in the reading.
