EMC Question of the Week: July 3, 2023

Keyboard key labeled "Reset"

Which of the following is a name commonly used to describe hardware or software that monitors a system and implements a reset when problems are detected?

  1. watchdog
  2. squirrel cage
  3. mother hen
  4. eagle scout


The best answer is “a.” A watchdog timer is hardware or software that monitors the time required for a task to be completed. If the time exceeds particular threshold, the timer will reset the process or system. Similarly, a watchdog processor may monitor a variety of system parameters or outputs from the main processor and reset that processor when it is apparent that it is locked up or confused. 

Watchdog circuits can play a key role in meeting certain immunity requirements, particularly transient immunity or ESD requirements. These circuits don't reduce the probability of interference, but they can change how the system reacts to that interference. Watchdog circuits are often the difference between a failure that requires human intervention versus one that doesn't.

Of course, a poorly designed watchdog can also be the cause of emissions or immunity problems. It is important that watchdog circuits are designed with the same attention to potential EMC issues as the other circuits in a system.

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