Please let me know what are the probable root causes for the failure of a Aanlog Input Module. In our plant its been observed that frequent failure of Channel faiure.
Please find an issue which i have attended in our plant, likewise observed for different water plant systems.
what will be the reson behind that, one observation was the two wire tranmitter instrument earth no where connected to earth terminal. please guide me on the same.
PW-II/DS-05/HMI-01 system Heater inlet temperature reading continuously showing as 159.8 degC on the HMI display irrespective of the process conditions.
Verification checks performed:
- Wire continuity test all the way from Power supply to Transmitter to PLC– Found OK
- Measured RTD (Radix make) Sensor Output – got 115 ohms = 39.96 degC – Found OK
- Transmitter Working condition- by connecting it to the other working channel of the PLC card – Found OK , please let me know if there is any other way to verify trasmitter is working or not?
- Measured loop current b/w Power supply TransmitterPLC– measured 0.4 milli amps – found NOT OK. Should be measured in b/w 4 to 20 milli amps as per RTD output resistance 115 ohms.
- 4 to 20 milliamps source applied to directly to PLC card IN2+ & IN 2- Terminals– No response from the PLC, on and the reading still showing on the HMI as 159.8 degC – concluded PLC Analog input channel gone bad.
Analog input card channel IN2+ and IN2- terminals are gone bad.
AI card Model: IF4 & Make: Allen Bradley shall be procured , escalated the same to Mr.Ashok.
Note: Currently no SPARE available in the PLC system.