Sterling STT40, STT70 manual Using a Thermocouple, Using a Platinum Resistance Thermometer, Problem

STT40 / STT70

Problem	Possible cause	Corrective action
No setting change possible on	The key protection switch is set	Set the key protection switch to
temperature controller.	to ON.	OFF.
	Input polarity on thermo-couple	Properly wire the terminals.
	is wrong or connection is wrong.
	Input-type setting is incorrect.	Properly set the input with the
		input-type selector rotary
		switch.
	No compensating lead wires	Use proper compensating lead
	used for extension of the
		wires and terminals.
	thermocouple.
		Use a dedicated thermocouple
	Thermocouple and controller are	connector. If a connector is a
	connected by wires other than	metal different from the
Process value is abnormal or	proper lead wires.	thermocouple and controller, a
not obtained.		temperature error may result.
	Process thermocouple not in	Verify that the thermocouple is
		properly installed in the inlet
	airflow.
		tube.
	Sensor is broken or short-	Replace with a good sensor.
	circuited.
	The controller is influenced by	Separate input wires as far as
		possible from the origin of the
	noise or other induction.
		noise.
	Celsius temperatures used	Check to see that proper
	instead of Fahrenheit or vice	temperature setting is in the
	versa.	temperature controller.

9.2. Determining Temperature Controller Errors or Sensor Errors

Using a Thermocouple

If the controller displays a temperature that is close to room temperature (70ºF/21ºC) when you short-circuit controller input terminals, the controller is normal and the sensor is probably broken, short-circuited, or incorrectly wired.

Using a Platinum Resistance Thermometer

If the controller displays a temperature of about 0.0°C (32ºF) when you insert a 100- ohm resistor between terminals A and –Bof the controller, and you short-circuit controller terminals +B and –B, the controller is normal and the sensor is probably broken, short-circuited, or incorrectly wired.

Other service problems or questions can be answered by contacting the Service Department.

Troubleshooting 9-4