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Alarming From a PLC or ModBus Device

Overview

Thousands of processes are controlled by dedicated programmable logic controllers (PLC). Many of these are installed on critical processes or unattended operations that periodically have issues that need to be addressed in a timely fashion.

The DiaLog Scout PLC, Elite PLC and Elite 200 all monitor, alarm and perform control functions to and from PLCs or other Modbus RTU devices.

Typical uses include:

  • Monitor PLC registers and perform alarm notification when limits or conditions fall outside normal settings.
  • Provide a local user interface allowing users to view and modify register values from the front panel of the DiaLog products.
  • Provide remote access to values in the PLC, even allowing modification of register values. For example, call in to check the frequency that a Variable Speed Drive is set to and modify it.
  • Provide a hardware-based alarm system for SCADA and HMI packages by allowing the DiaLog products to be either a Modbus Master or Modbus Slave.
Scout PLCEliteElite PLCElite 200/500
Alarm call-out to pagers/phones
Status call-in
Alarm call-out to alphapagers, fax and modem 
Number of registers to read/write12 or 24From 8-72From 8-72200-500
Type of registers supportedR/W coils
R/W holding
R input
R register
R/W coils
R/W holding
R input
R register
R/W coils
R/W holding
R input
R register
R/W coils
R/W holding
R input
R register
Physical I/O04-48 digital
8-48 analog
4-24 relays
00
Programming via front panel
Programming via PC 
Programming via phone