Lightwave Communications LDT-5525 manual Calibration Adjustments, Thermistor Calibration

MAINTENANCE AND TR OUBLESHOOTING

Calibration Adjustments

Calibration Adjustments

C H A P T E R 3

There are two calibration adjustments that need to be made for the LDT-5525 Temperature Controller. They are calibration of sensor measurement, and calibration of the ITE current measurement and limit circuits.

If a problem arises during calibration which prevents its normal completion, the calibration may be aborted with no ill effects by simply pressing the OUTPUT switch. This is possible because the calibration values are not saved to non-volatile memory until the last step of each calibration procedure.

Thermistor Calibration

The following procedure is for calibrating the 100 µA and 10 µA constant current sources so that the thermistor resistance measurements for these ranges will be as accurate as possible. This procedure calibrates the resistance measurements of the thermistor. This procedure does not calculate C1 and C2. For information on calibrating the thermistor sensor, see Appendix A.

Calibration may be aborted by pressing the OUTPUT switch.

aSet the SENSOR SELECT switch (back panel) to the 100 µA position. Set C1 to 0.99, C2 to 2.57.

bMeasure and record the exact resistance of your 4 KΩ, 40 KΩ, and 400 KΩ metal film resistors. A 4-point probe resistance measurement is recommended.

cConnect the 4 KΩ metal film resistor to the sensor input of the LDT-5525 Temperature Controller (pins 7 and 8).

dEnter the sensor calibration mode by pushing the MODE and SENSOR CAL switches at the same time. After this, the display will indicate the sensor resistance in KΩ. Allow the measurement to settle for about three seconds.

ePress and hold in the ENBL switch and turn the ADJUST knob until the display indicates the same resistance you recorded for the 4 KΩ metal film resistor.

fRelease the ENBL switch and wait for the VIEW SET indicator (LED) to be unlit. Replace the 4 KΩ resistor with the 40 KΩ metal film resistor (for 100 µA) or 400 KΩ metal film resistor (for 10 µA). After three seconds, repeat Step e with this resistor. Ten seconds after the ENBL switch is released, the LDT-5525 Temperature Controller will store the calibration data in non-volatile memory.

Press the DISPLAY switch three times to rotate the display back to the SENSOR mode.

gSwitch the SENSOR SELECT switch to the 10 µA position and repeat Steps c - f.

hAfter calibration, the I LIMIT will be automatically set to 4.00 Amps. Reset the I LIMIT to the desired value.

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