BlueDelta developed the WD601 Watchdog unit to monitor the PLC execution cycle.

Although modern PLC systems have an internal watchdog unit it can be necessary to monitor the PLC externally. The WD601 watchdog unit is developed for this purpose. It can easily be monitored and most important it can be demonstrated during factory acceptance tests. Which can be a real hassle with internal PLC watchdog timers.

WD601 PLC Watchdog unit

Recently the WD601 was used in a project with remote I/O stations. The WD601 was connected to the remote I/O station in order to monitor the field-bus connection to the remote I/O station. When something goes wrong with this connection the status of the I/O station is no longer updated, this is monitored by the WD601. When this happens, the machine connected to the remote I/O station is shut down in a safe state by means of hard-wired safety valves.


  • Build with passive components, this will ensure fail safe operation.
  • DIN rail mounting.
  • Optical isolated feedback signal to the PLC. It can be used with both NPN and PNP inputs.
  • 24VDC operation.

You will find more information in the wd-601-product_data_sheet