Communication Signal Error

You miss out what is probably the most important information.
Was the system working and has now failed? Or has it never worked correctly?
Set up a similar pressure transduce (A), on a short length of cable connecting to the PLC, all set up in the control room. This will give you a chance to play with communication settings and suchlike.
Check that you can get that all working ok. If that is ok, then take the pressure transducer (A) out to where the problem one is. Connect (A) to the cable run, if it is all still working fine then the cable is ok and the installed transmitter is faulty, if it's not ok there is a wiring problem.
Apply basic fault finding techniques slowly and methodically.
The alternative is to run around randomly changing things and panicking, a practice best left to trainees and managers.
Del

Thanks alot Del. Yes, the system had been working well and suddenly start showing this error when the former faulty HART 3051 Pressure transmitter (0-300psi) was replaced with a new one(0-10,000psi) and was re-ranged(0-800psi); After the installation, it was OK, but after awhile the fault surfaced. So, can a new transmitter display correct values on the LCD display and display different values on the OMNI?

So, can a new transmitter display correct values on the LCD display and display different values on the OMNI?
No idea I have no experience with that equipment, but if there is a length of cable and a communication protocol involved anything can happen!

Maybe a scope or serial data analyser is called for. It seems too much of a coincidence for more than one unit to fail in the same manner, so maybe the fault is in the wiring or at the receiving end... or good old finger trouble.
'Re-ranged' worries me... I'd leave everything exactly as it was, only change one thing at a time if possible.
Good luck
Del

ThankGod,

Can you tell us the model (serial complete) for this pressure transmitter?

As mentioned above, it is very important to know what kind of output signal are you using, is it 4-20mA or Hart digital signal?

the new transmitter was re-ranged, but how about the OMNI counts in order to display the correct value?

Regards

JP

Just change the range of PT in OMNI from 0-300 to 0-800, this should solve your problem

Thanks alot Srinivasanp, I had just done that; that was the problem. Am grateful.

I also want to thank all that contributed to this success.

Wow, that is a 10:1 turn-down ratio, may make the output real sensitive to "PV" changes.

>"may make the output real sensitive to "PV" changes."

If the transmitter's output is used as a PV input to a PID loop, the PID loop's output will not be more sensitive (aggressive) with the scale change; on the contrary, a PID output would be more sluggish.

The original 4-20mA scale represented 0-300 psi, the re-ranged scale is 0-800 psi.

A 6 psi error on the 300psi scale is only 2% error.
A 6 psi error on the 800psi scale is only a 0.75% error.

For the same PID tuning constants, a 0.75% error will call for less output change than will a 2% error.

Pray to God to tell you the answer. If He actually does, then ThankGod.

You must recalibrate(re range) the receiver to the same scale as the transmitter.