THORLABS ITC502, Operation Manual

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1.4 Mode of operation
ITC500 / page 6
1.4 Mode of operation
A fixed adjustable hardware limit limits the maximum deliverable laser current in each
operating mode.
The laser diode is sourced unipolar against ground (anode or cathode to ground may
be selected). This is of advantage regarding the stability of the laser current, noise
and RF influences.
The monitor diode input is a transimpedance amplifier (input impedance 0
Ω
). Both
polarities of the monitor diode can be selected. The monitor diode may either be
operated photovoltaic (without bias voltage) or photoconductive, i.e. with bias voltage
(selectable in a range from 0 ... 10 V).
The limit value for the TEC current and the temperature window are set with screw-
driver potentiometers.
The TEC element always operates against ground. This is of considerable advantage
regarding the safety of the TEC element and the stability of the TEC current.
The sensor input is designed for different types of temperature sensors.
A missing sensor or the selection of a incorrect type will be detected.
The ITC5xx has an input for an IC temperature sensor of the AD590/592 or
LM35/135/335 series as well as an input for a thermistor. If a thermistor is used you
can choose between two resistance ranges (maximum resistance of the thermistor
20 k
Ω
or 200k
Ω
).
The set values for the temperature and the thermistor resistance are set with the 10-
turn main dial knob.
The P-, I- and D-share of the analog control loop are set with „thumb-nail“-
potentiometers.
All settings are done by the operating elements or via the IEEE488-interface (ITC5xx-
IEEE) and a PC. Only the hardware limits for the currents must be set manually. No
manual settings are required during automatic tests using a PC.