Lm335 Sensor Calibration; Ite Current Calibration - ILX Lightwave LDT-5525 User Manual

3.3.3 LM335 Sensor Calibration

The following procedure is for calibrating the LM335 sensor measurement so that the temperature measurement will
be as accurate as possible. This procedure calibrates the voltage measurement of the LM335. This procedure does
not calibrate C1 and C2. For information on calibrating the LM335 sensor, see Appendix C.
Calibration may be aborted by pressing the OUTPUT switch.
a. Set the SENSOR SELECT switch (back panel) to the LM335 position. Set C1 to 0.00, C2 to 1.00.
b. Connect a precision 4 KΩ metal film resistor and a precision voltmeter in parallel at the sensor input of the
LDT-5525 Temperature Controller (pins 7 and 8).
c. Enter the sensor calibration mode by pushing the MODE and SENSOR CAL switches at the same time. After
this, the display will indicate sensor reference voltage in mV. Wait for three seconds for the measurement to
settle.
d. Press and hold in the ENBL switch and turn the ADJUST knob until the display indicates the same voltage
as shown on the precision voltmeter multiplied by 10. For example, if the voltage across the resistor is 1.9871
Volts, turn the ADJUST knob until the display reads 19.87.
e. Release the ENBL switch and wait for the VIEW SET indicator (LED) to be unlit. Replace the 4 KΩ resistor
with a 10 KΩ metal film resistor. After three seconds, repeat Step d with the 10 KΩ resistor. Ten seconds
after the ENBL switch is released, the LDT-5525 Temperature Controller will store the calibration data in
non-volatile memory.
f. Press the DISPLAY switch three times to rotate the display back to the SENSOR mode. After calibration, I
LIMIT will be automatically set to 4.00 Amps. Reset the I LIMIT to the desired value.

3.3.4 ITE Current Calibration

The following procedure is for calibrating the ITE constant current source for both polarities of current. During this
procedure the ITE current is driven to a series of pre-determined values. When each of these values is reached and is
stable, the user enters the actual value of the current, as measured by an external DMM. The LDT-5525 Temperature
Controller then automatically calibrates the TEC current source and limits.
Calibration may be aborted by pressing the OUTPUT switch.
a. Set the sensor select (back panel) switch to "100 uA." Set C1 to 0.99, C2 to 2.57. Connect an (approximately)
15 kΩ resistor to the sensor pins (7 and 8). Connect a 1 Ω, 20 W, resistor across the TEC output terminals
(pins 1 and 3) and use a calibrated DMM to measure the voltage across the resistor. Calculate the current in
the following steps by using Ohm's Law:
-where E is the accurately measured voltage across the resistor, and R is the accurately measured load
resistance. A 4-point probe resistance measurement is recommended.
I = E / R
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