Wavelength Electronics WTC32ND, Datasheet And Operating Manual

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WTC32ND TEMPERATURE CONTROLLER
TROUBLESHOOTING
PROBLEM POTENTIAL CAUSES SOLUTIONS
Temperature is decreasing
when it should be
increasing
-OR-
Temperature is increasing
when it should be
decreasing
The TEC may be connected
backwards to the WTC
The convention is that the red wire on the TEC module connects to
TEC+ (Pin 12) and the black wire to TEC- (Pin 11). If your TEC is
connected in this manner and the problem persists, the TEC module
itself may be wired in reverse. Switch off power to the system, reverse
the connections to the WTC, and then try again to operate the system.
TEC wiring polarity is dependent on temperature sensor type (NTC vs.
PTC). Verify that the polarity is correct for the sensor type you are using
(see Table 7. OUTA & OUTB Wiring Configuration on page 18 ).
Temperature increases
beyond setpoint and will
not come down.
The heatsink may be
inadequately sized to dissipate
the heat from the load and
the TEC module, and now the
system is in a condition called
thermal runaway
- Increase the size of the heatsink, add a fan to blow air over the heatsink,
and/or reduce the ambient air temperature around the heatsink.
- Apply a thick layer of thermal paste or use thermal washers between
the load, the TEC surfaces, and the heatsink.
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 may be needed. Consult our
Technical Note
TN-TC01: Optimizing Thermoelectric Temperature
Control Systems
and Application Note
AN-TC09: Specifying
Thermoelectric Coolers
.
Temperature does not
stabilize very well at the
setpoint
There may be poor thermal
contact between components
of the thermal load
Use thermal paste or washers between the load / TEC and the
TEC / heatsink interfaces. Ensure the temperature sensor is in good
thermal contact with the load.
Unit may be 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 / ºC, whereas an RTD
sensor has a sensitivity of 4 mV / ºC.
Proportional control term may
be set too high
Reduce the value of the proportional term. For more information,
reference our technical note TN-TC01: Optimizing Thermoelectric
Temperature Control Systems .
Heatsink may not be sized
correctly or may not have
adequate airflow
Ambient temperature disturbances can pass through the heatsink and
thermoelectric and affect the device temperature stability. Choosing a
heatsink with a larger mass and lower thermal resistance will improve
temperature stability. Adding a fan across the thermoelectric’s heatsink
may be required.
Temperature does not
reach the setpoint
Current driven to the TEC or
heater may be insufficient
Increase the current limit – but DO NOT exceed the specifications of
the TEC or heater.
The controller may not have
sufficient compliance voltage to
drive the TEC or heater
Increase the power supply voltage; be certain to verify that the controller
is within the Safe Operating Area with Wavelength’s Temperature
Controller SOA calculator:
www.teamwavelength.com/support/design-tools/soa-tc-calculator/
The sensor may not have good
contact with the heatsink and
load.
Use thermal paste or washers between the load / TEC and the
TEC / heatsink interfaces. Contact the thermoelectric manufacturer for
their recommended mounting methods.