Today is...
Thursday, May 24, 2018
Welcome to Control.com, the global online
community of automation professionals.
Featured Video...
Featured Video
EtherCAT with CTC’s master lets your multivendor network play well together...
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
New Valve Feedback Signal Woes
Replaced a Jordan MV-1020 with an RCV SEVA-200. Feedback 4-20 gives constant 100% open indication at HMI regardless of valve position.

Replaced a Jordan MV-1020 with an RCV SEVA-200. Feedback 4-20 gives constant 100% open indication at HMI regardless of valve position. Two identical valves were replaced and both act the same way (yes, I broke both of them). My predecessor had replaced other valves with an older model (non-SEVA)of RCV valve with success.

I have connected my Fluke process meter to both the valve output signal and have simulated a feedback signal to the PLC with valid indications for both tests. The selector switch is at position 3 for 4-20 signals. I have verified polarity and in a fit of frustration have tried reversing the signal wires (my plant has unique properties. Depending on which contractor did an installation black may be - or +).

Any pointers for where to look next?

By W.L. Mostia on 16 March, 2018 - 11:53 am

Did you read the 4-20mA signal from the RCV SEVA 200? It appears that the RCV SEVA-200 has an active (4-wire) 4-20 mA output rather than the 2-wire sensor signal from a transmitter that your HMI typically expects. I believe that it is also grounded at the RCV SEVA- 200, which would require an isolated input at your control system.

William (Bill) L. Mostia, Jr. PE
ISA Fellow, FS Eng. (TUV Rheinland)
WLM Engineering Co.