Calibration Adjustments; Thermistor Calibration - Newport LDC-3706 Series User Manual

Calibration Adjustments

There are sixteen calibrations that need to be completed for proper operation of the LDC-3706
Laser Controller. These calibrations pertain to temperature sensor measurement, the I
measurement, the TEC voltage measurement, the laser source current measurement, the laser
source voltage measurement, and the photodiode current measurement.
If a problem arises during calibration which prevents normal completion, calibration may be
aborted by allowing the calibration procedure to time out by not pressing any front panel
buttons, turning any knobs, or sending any remote commands. This prevents alteration of stored
calibration values due to the fact that new values are not saved to non-volatile memory until the
last step of each calibration procedure is complete.

Thermistor Calibration

The following procedure calibrates the 100 µA or 10 µA constant current sources so that
thermistor resistance measurements will be accurate. This procedure does not calculate C
and C . For information on calibrating the thermistor sensor, see Application Note #4
3
Thermistor Calibration and the Steinhart-Hart Equation.
The first part of the calibration is to determine an accurate value for the sensor current (10 µA or
100 µA). Thermistor resistance measurements require that the IC-V calibration procedure has
been performed. The order in which the procedures are performed is not important.
1. Connect a DC ammeter to the sensor pins of the 15-pin output connector of the LDC-
3726 (pins 7 and 8) or the 25-pin output connector of the LDC-3736/LDC-37620 (pins 14
and 15). (Note: the current from the sensor pins should be less than 120 µA.)
2. Enter the sensor calibration mode by navigating to the "100 µA Cal" or "10 µA Cal"
selection in the Sensor Cal area of the Calibration submenu of TEC parameter menu
tree. Press the SET button to select the calibration, and then press the TEC button to
start it.
3. Turn the ADJUST knob until the display indicates the same current measured by the DC
ammeter.
4. Press the TEC button and wait for the 7-segment display to exit the calibration mode.
Once the calibration is completed, the calibration constants will be stored to the non-
volatile memory and the display will return to its previous state.
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LDC-3706 Series Laser Controller
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