unstable analog input

[harrydeharry]

Dearall,
I am using a Delta SS2 PLC with 6xa analog card,
[ TO K0 K1 H480 K1]
using first two analog inputs ans 0~10 v dc input and rest of the two as
4~20 ma, if I check my input from the device in a form of 4~20 its coming stable, while checking on plc it is very unstable, while i have checked it with shelled cable, groundings, other noises etc.

Please suggest what cud go wrong as i had not used delta as well as analog much.
BR

 

[DwSoFt]

Well the shield should only be. connected at 1 end so the interference drains instead of causing a ground loop. secondly it is possible your meter isn't fast enough to.detect the changes the Plc is seeing. you can make averaging logic to smooth the signals out.

 

[swilkes]

Common mode voltage

Harry,

What is the common mode voltage between the channels? Most analog input cards can deal with 5 vdc between the channels, but any large difference will cause problems.

Steve