TCR-M Potentiometer Calibration and Output Test Guide

The TCR-M temperature controller is a digital dial controller used for simple ON/OFF heating control. In the field it is often necessary to check the controller without a real sensor fitted, or to confirm that the relay output switches correctly at the setpoint. This guide shows how to use a potentiometer to simulate the sensor input, set the process value (PV) and setpoint (SV), and verify the relay output (OUT).

Watch the TCR-M potentiometer calibration and output test procedure.

Safety Before Testing

• Wire the controller with the power disconnected. Confirm the supply is isolated before making any terminal connection.
• The relay output test is carried out with the controller powered, so the output terminals can be live. Only qualified personnel should perform live output checks.
• Do not touch bare terminals or probe the output side while power is applied.
• Use a potentiometer only to simulate the sensor input side of the controller; never apply external voltage to the sensor input unless the controller documentation permits it.

Wiring and Pre-checks

• Confirm the controller is set to the sensor type you intend to simulate (thermocouple or RTD), as listed on the TCR product page.
• Wire the potentiometer to the sensor input terminals following the controller’s terminal layout for the selected input type.
• Set the potentiometer to its starting position before applying power so the simulated PV begins at a known low value.
• Keep the test leads short and away from the load wiring to avoid pickup on the low-level sensor signal.

Potentiometer Calibration

1. Apply power to the controller and confirm the display lights and shows a reading.
2. Adjust the potentiometer slowly and watch the displayed PV change. This confirms the input path is working and the controller is reading the simulated signal.
3. Set the SV using the front dial to the target temperature you want to test.
4. Move the potentiometer so the PV rises toward the SV, then past it, and confirm the display tracks the change smoothly.
5. Return the potentiometer to bring the PV back below the SV and confirm the reading falls as expected.

The aim of this step is to confirm the controller reads the simulated input and that the dial SV is accepted, not to set an absolute calibration value. The display accuracy of the TCR series is given on the product page.

Output Test Procedure

1. With the SV set on the dial, raise the PV (via the potentiometer) until it is below the SV. The relay output should be in the heating state.
2. Continue raising the PV until it crosses the SV. The relay output (OUT) should switch.
3. Lower the PV back below the SV and confirm the relay switches back to the heating state.
4. Repeat the rise and fall once or twice to confirm the switching is repeatable around the setpoint.

The output is a relay contact. Confirm switching only at the output terminals; do not introduce a load beyond the relay rating shown on the product page.

How to Interpret the Result

• If the PV tracks the potentiometer smoothly and the relay switches each time PV crosses SV, the controller input and output are functioning.
• If the PV does not change when the potentiometer is adjusted, check the input type setting and the potentiometer wiring to the input terminals.
• If the relay does not switch as PV crosses SV, re-check the SV set on the dial and confirm the PV actually reaches and crosses it.
• If the display jumps or is unstable, reduce lead length and check for pickup on the sensor input wiring.

Common Problems

No PV change when adjusting the potentiometer

The input type setting or the potentiometer wiring to the sensor input terminals does not match. Confirm the selected input type and re-check the connection.

Relay does not switch at the setpoint

Confirm the PV is actually crossing the SV shown on the dial. A dial set to the wrong value, or a PV that does not reach the SV, will keep the relay in one state.

Unstable or jumping display

Low-level sensor wiring picks up noise. Keep the potentiometer leads short and away from load cabling.

FAQ

Why use a potentiometer instead of a real sensor?

It lets you test the controller input and relay output quickly on the bench or in the field without fitting a sensor or heating the process.

Does this calibrate the controller to a real temperature?

No. It confirms the input reads a simulated signal and the output switches at the setpoint. Absolute accuracy depends on the real sensor and the controller’s stated display accuracy.

Can I test the relay with a real load connected?

Only if you are qualified and the load is within the relay rating on the product page. The live output test should be performed by qualified personnel.

Related Product

Full specifications, input options and relay ratings for this controller are on the TCR digital dial temperature controller product page. For help selecting a controller for your process, contact Strong Electric.