ILX Lightwave LDT-5900 Series User Manual page 54

2
C H A P T E R
that the controller supplies. See "Limits" under the Parameter section in Chapter 2
to set the appropriate limits for your TE.
It is normal for the controller to operate at the current limit, especially when the
load temperature is far from the setpoint. The current limit LED will illuminate
green when the controller is in a current-limit condition.
If the heatsink is too small for the application, the heatsink eventually becomes
heat saturated condition where heat is being transferred to the heatsink faster
than the heatsink can dissipate the heat. When the heatsink becomes saturated,
the TEC current increases in an attempt to cool the load; this additional current
creates more heat than can be dissipated and subsequently, more TEC current is
applied. This situation is sometimes referred to as thermal runaway, and can
cause a load and TEC to become damaged. The current limit LED will illuminate
RED in a thermal runaway condition, (i.e. the current is running at its limit and the
temperature is moving away from the setpoint).
To help avoid thermal runaway damage, the LDT-5900 Series Temperature
Controller provides a high-temperature limit setting. When the load temperature
exceeds the High Temperature setting, the LDT-5900 turns off the TEC current
and generates an error. Using GPIB, you can disable the high-temperature limit
from turning off the controller. See Chapter 3, Output Off Registers and Chapter 4,
Command Reference for more information about disabling or enabling conditions
that turn off the controller.
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LDT-5980/ 5948
O P E R A T I O N S
Ba sic TEC Op era t ion Inst ruct ions