I have a Monitoring system using MODBUS slaves and a SCADA as the master. what would be the easiest way of having a local alarm (near to the monitoring devices)? The alarm cannot be controlled from the SCADA, in case of communication failure/cut cable etc.

Would I need two masters?

Any help would be appreciated.

Scott

 

Modbus slave units frequently have Modbus as an option or secondary output, with a primary output like a relay or an analog signal, depending on what the slave unit is.

If there are no outputs other than Modbus and it's Modbus RTU over RS-485, then you cannot use another RTU master. But you could use the Precision Digital 865 "Snooper" meter to capture any value that passes in traffic and to alarm based on that value.

In Snooper mode, the 865 monitors the serial traffic between the master and the slave. The 865 will 'read' any specified register value that is in the passing master-slave traffic, capture that value as its primary PV value, display the value and alarm on it (multiple alarm relays).

There are separate configuration settings for high or low alarming with adjustable deadbands.

http://www.predig.com/PD865/

 

HI Scott,

I am not sure what triggers your alarm. I am assuming an input or a series of inputs. If this is case, I would suggest our WISE-7160. This module has 6 DI and 6 DO (relay) which can be locally controlled using If-Then-Else logic. This module is also a Modbus TCP slave device which can be polled using the Ethernet port by your SCADA software.

http://www.icpdas-usa.com/wise_7160.html