TC_LAB datasheet(20/29 Pages) WAVELENGTH

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TROUBLESHOOTING

Table 5. Troubleshooting

PROBLEM

POTENTIAL CAUSES

SOLUTIONS

Front panel Power button does not

turn on

The button has been pushed on and off

within 3 seconds.

The front panel Power button has a 3 second

delay between when it is turned off and on in rapid

succession. This is a safety mechanism to ensure

there is no damage to either the TC instrument or

the attached load.

The rear panel switch is off.

Turn the rear panel switch to the on or | position.

Temperature increases beyond the

setpoint and will not come down

The TEC and heatsink are not adequately

sized for the thermal load

The heat being generated by the load may be

too great for the TEC to pump to the heatsink; a

larger TEC or heatsink, or airflow may be needed.

Consult Technical Note TN-TC01: Optimizing

Thermoelectric Temperature Control Systems.

Temperature does not stabilize very

well at setpoint

Poor thermal contact between components

of the thermal load

Use thermal paste or washers between the load/

TEC and TEC/heatsink interfaces. Make sure the

temperature sensor is in good thermal contact with

the load.

Operating outside of the ideal region of the

temperature sensor

The sensor type and bias current should be selected

to maximize sensitivity at the target temperature.

Thermistors provide the best performance,

particularly for applications where a single setpoint

temperature must be accurately maintained.

For example, at 25°C a 10 kΩ thermistor has a

sensitivity of 43 mV/°C, whereas an RTD sensor

has a sensitivity of 4 mV/°C.

Proportional control term is set too high

Run an IntelliTune scan.

Derivative term is introducing noise.

Run an IntelliTune scan.

Using a resistive heater, temperature

is slow to stabilize and is not within the

specifications

Setpoint temperature is set too close to the

ambient temperature

Set the temperature at least 10°C above ambient

when using a resistive heater. A resistive heater

is unable to precisely maintain temperatures near

ambient because once the temperature overshoots

the setpoint, the controller turns off and relies on

ambient temperature to cool the load. If setting the

temperature 10°C or more above ambient is not

possible, then choose a thermoelectric, which can

alternately heat and cool the load to maintain a

more precise setpoint temperature.

Airflow across load is inadequate.

Use a fan to blow air across the load to increase

natural convection.

Temperature does not reach the

setpoint

Insufficient current driven to the TEC or

heater

Increase the current limit - but DO NOT exceed the

specifications of the TEC or heater.

The controller does not have sufficient

compliance voltage to drive the TEC or

heater

Check the thermoelectric voltage and determine if

it is too close to the 15 V maximum. If it is, choose

a lower voltage thermoelectric.

Actual temperature does not approach

setpoint after output current is enabled

Thermoelectric wiring is reversed.

Reverse the leads to the thermoelectric.

The thermoelectric is generating too much

heat and has inadequate cooling

Install a larger heatsink or a fan to cool the heatsink.

I hear a beep and know there is an

error, but nothing is displayed on the

instrument screen

A remote command REMERR needs to be

set to 1 to display errors

Connect the TC LAB instrument to a remote

computer and write the REMERR 1 command.

See the Remote Command Set document for more

information.

Can’t clear an on-screen error

message

The cause of the error may not have been

fixed.

Press the enable button once. If the cause of

the error is not corrected, the error message is

displayed again.

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