field device failure - request for experiences


Thread Starter


Transmitter particulars- Yokogawa DP Harp transmitter model EJA 110A.

I am having problems with this smart diff presure transmitter used for vessel level monitoring. The output flunctuates without any apparent reason, after which it becomes steady without any intervention. The supply voltage is confirmed to be steady at 12Vdc. I would like feedback from anyone who has had experiences with this type of failure.

Also I would like to know if this behaviour is temporary or if it leads ultimately to total failure.

question. has this problem just raised its head or has it been with you since installation?
Usally something like this can be traced to earth interference. Has there been work carried out in the vicinity or on the cable? Is it a corrosive environment and as a copncequence deteriation of conections has occured. Is your 12 volt supply sufficient to handle the resistive load? (maybe 24volt is a better option)
Most situations are different and require some local knowledge to resolve.

hope this helps.

Dear Ben,
Isn't 12 VDC on the borderline? why not try the same with a higher supply voltage. And what is the load resistance? If I remember correctly, the load resistance was 650+ ohms at a nominal 24 VDC power supply. Hope this helps


Brian T. Smith

You did not mention how much the output fluctuates. Is there turbulence in the process fluid at certain times that would cause a level measurement fluctation? When it is fluctuating, block in the level transmitter to see if it becomes steady. If it does you have a process problem rather than an Instrument problem. If it does not then it is your level transmitter. Check for loose signal and ground connections, water in Instrument electrical housings and conduit.
Good luck troubleshooting!