Leave the immersion exactly as it is, but with it's integral thermostat set higher than the temperature you actually want to achieve.
Then strap the new sensor to the cylinder and wire your additional temperature controller in the mains supply to the immersion, as you would a time switch for example.
That way you are using your PID controller to get the temperature you require, but integral thermostat will take over should something go amiss.
Then strap the new sensor to the cylinder and wire your additional temperature controller in the mains supply to the immersion, as you would a time switch for example.
That way you are using your PID controller to get the temperature you require, but integral thermostat will take over should something go amiss.
