Linking Yokogawa Centum to Sprecher&Schuh Motor Protection Relays


Thread Starter

Andray AC Bath

I am currently involved with setting up a MODBUS link between an ACM12 card (Yokogawa Centum CS DCS) and a number of Sprecher&Schuh CET4 Motor
Protection Relays. The field wiring for the job is complete and now we are having problems configuring so that communication works. The only
configurable parameters on the CET4 are Baud Rate & Station Number.

Also, Do we need a terminating resistor at the end of the chain? (We have a 120ohm resistor at the ACM12 card as per the Yokogawa manual - however do we need one at the other end?)

Any help would be greatly appreciated as it is important that we get this functionality working before plant startup (20th June).

Thanks in advance.

Alvin C. Cipriano

Hi There

Be sure you have declared the right Function Code for both controller, you can see if the controller responnds to the slave thru the CS Software communication monitor you can see bits that are triggered in case your communication is established ............

Alvin C. Cipriano
Systems Integration Manager
Rockwell Automation Authorized System Integrator
I have experience only with ACM12 in Yokogawa CS1000/3000 systems, but I think is the nearly the same. I prefer 4 wire connceting (default), but I have tested also 2 wire (2w/4w switch is under cover). On the ACM12 side I always use resistor (delivered with card), on the other side I usually don't use it (but manual says it has to be used). I have connected ACM12 and MTL multiplexer (MODBUS) and it's worked fine. Now I am going to connect CS1000 with Simatic S7 and Woodward 505 (two ACM12 in one nest).