Watchdog Signal and Timer Setup

A controller provides two watchdog functions. The first is a watchdog (life) signal that can be monitored by an external system to verify that the controller is operating correctly. The second is a watchdog timer that automatically restarts the controller if it becomes unresponsive.

A watchdog (life) signal is always generated and can be monitored via a digital output or a virtual variable. By default, a dynamic life signal with the fault condition “on no error” is configured, which acts as the overarching condition for all fault states. When no error is present, the signal toggles between ON and OFF. If an error occurs, the signal remains continuously ON.

To modify the default watchdog signal settings or activate the watchdog timer, go to Controller settings → Watchdog.

Watchdog Type

Off: The watchdog timer is inactive and does not trigger a restart if the controller becomes unresponsive (default setting).
Reset on retrigger timeout: The watchdog timer is active and automatically triggers a restart if the controller becomes unresponsive and the retrigger time expires.
- Watchdog Start Delay [s]: The watchdog timer activates 30 seconds after system start (once measurement mode is initiated). This start delay can be extended if required.
- Watchdog Retrigger Time [s]: Defines the interval within which the controller must retrigger the watchdog timer to prevent a restart. The minimum interval is 10 seconds. Increase this value for applications with slow measurement cycles to reduce energy consumption. On a Q.monixx, the retrigger time is fixed at 60 seconds.

On a Q.monixx, the watchdog timer (“Reset on retrigger timeout”) behaves differently than on a Q.station. Once activated, it cannot be stopped via software. A configuration change does not disable it, only a device restart will stop the watchdog timer.

Life Signal Type

Dynamic: The watchdog (life) signal toggles between ON (high) and OFF (low). Use the “Use variable as output” function to assign the signal to a digital output or virtual variable. In dynamic mode, the selected fault conditions are combined using a logical AND.
- Lifesignal Toggle Time [s]: Defines the interval (half period) at which the dynamic signal toggles between ON and OFF. The default is 1 second, and the maximum is 60 seconds.
Static: The watchdog (life) signal on Digital Output 1 is OFF (low) when no fault is present and switches to ON (high) in the event of a fault. Use the “Use variable as output” function to assign the signal to a digital output or virtual variable. In static mode, the selected fault conditions are combined using a logical OR.

Use variable as output

Option to output the watchdog signal to a user-defined variable (e.g. a digital output or a virtual variable).

Fault conditions

For the watchdog signal, any combination of fault conditions can be selected to trigger an error. Depending on the selected signal type, these conditions are combined using either AND logic (dynamic) or OR logic (static).

The fault conditions are not applicable to the watchdog timer (“reset on retrigger timeout”) feature, which solely monitors whether the controller becomes unresponsive.

On no error: This fault condition acts as the overarching condition for all fault states listed below, which can also be selected individually if required.
On data port
On distributor port
On FTP
On TCP/IP
On UDP
On transparant port

Watchdog Signal and Timer Setup

Watchdog signal and timer function on Q.series controllers provide continuous system supervision and enable automatic restart when the controller becomes unresponsive.