Dan wrote:

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off.

When the defrost controller fails, the freezer freezes up

How about a low tech approach. You're not checking temp, but need to
know if the controller is cycling power.
Buy a cheap HH/MM/SS timer. Set it to NN hours. Put a relay coil across
the heating element terminals. Wire the relay contacts across the timer
reset contacts to reset the timer. If the timer is not reset, the alarm
goes off. The dog then barks, alerting you to the need to change
controllers.


Kevin Gallimore