Equipment: One Rosemount pressure transmitter, one Siemens 300 PLC
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Question: Both the pressure transmitter and the PLC are set to a range of 0-5 KP. At 0 KP, the pressure transmitter shows 0.02 KP, while the computer displays around 0.4 KP. The circuit current measured at the meter is about 4.1 MA, and the current measured at the PLC terminals is around 5.4 MA. By adding a resistor to the circuit and using a 475 tester, normal operation was restored, with both the meter and the computer showing around 0.02 KP. Have anyone else encountered a similar problem? What could be the cause? Thank you!
Was the resistance removed again and the original condition restored?
It should be interference; check the wiring to see if the shielding wire is connected and whether there is alternating current present in the transmission lines.
Where has the resistance gone? Try using a different power supply, such as one powered by a signal generator, instead of powering it with a card
Is this a HART instrument? If so, the resistance of the circuit being measured must be greater than 275 ohms for the signal to be normal. When debugging a HART instrument, a 250-ohm resistor needs to be connected in series in order to carry out the debugging process