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4.4 Thermoelectric cooler controller
The Laser Diode Controller contains one or two optional built-in controllers for thermoelectric coolers.
Cooler 1 is usually used for cooling the laser diode and delivered up to
±
13A@
±
48V. The cooler 2 is
optional and is used for customized applications (e.g.: laser crystal cooling). It delivered up to
±
3A@
±
5V. If a cooler is enabled, see menu COOLER, the appropriate temperature controller
immediately starts operating after switching on the instrument. The temperature controller attempts to
set the approptriate cooler temperature to the desired temperature which may take up to several
minutes depending on the difference of the actual temperature and the desired temperature. Due to
the large heat capacity and heat load of medium power and high power laser diodes and the needed
heatsinks, it may take some minutes until a stable operating point is reached.
The actual temperatures of cooler 1 “T1” (usually the laser diode), cooler 2 “T2”(optional) and the
current of cooler 1 “I1” are displayed above in the middle of the display.
The sign “+” means heating current, and “-“ cooling current of ”I1”.
Note:
The output of the thermoelectric controllers are bipolar, that means they can cool and heat.
Trouble-shooting:
After preparing the connection of the thermoelectric coolers and the temperature sensors according to
the section Connector pin-out and switching on the Laser Diode Controller, it might happen that the
temperature controller doesn’t seem to control the temperature, i.e. the measured temperature doesn’t
approach the desired temperature after some time or the laser diode is heated up instead of cooled
down.
In this case the polarity of the thermoelectric cooler referred to the pin-out as shown in the section
Connectors pin-out has to be changed. Simply change the connection of the two leads of the
thermoelectric cooler, even if the occurring labelling „Plus“ to „Minus“ doesn’t match obviously.
After this change the measured temperature should approach the desired temperature.
4.4.1 TEMPERATURE Menu
Within the temperature menu it can be set the temperature, the upper and lower temperature limit and
the control loop parameters of the PID-temperature controller for the first and second (optional) cooler.
Temperature
The value of the temperature can only be changed within the valid temperature range as defined by
the upper and lower temperature limit. The value for the temperature must be within 0°C to 50°C.
Confirm the value with the Enter key. The desired temperature is stored permanently in a non-volatile
memory, even when the instrument is switched off.
Temperature limits
The operating laser diode and also the optional custom application should be protected by operating
setting temperature limits according to the specific datasheet provided by the manufacturer.
If the temperature of cooler 1 or cooler 2 (provided they are enabled) are out of the selected range, the
laser diode turned off automatically and an error message appears on the display, see section Error
messages.
Confirm the value with the Enter key. The desired temperature limits are stored permanently in a non-
volatile memory, even when the instrument is switched off.
Note:
The instrument accepts only inputs where the temperature of the upper limit is higher than the
temperature of the lower limit.
The value for the upper and lower temperature limit must be within 0°C to 50°C.
Summary of Contents for ldc1000
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