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MAINTENANCE AND TROUBLESHOOTING
Calibration Adjustments
06_07 LDT-5525 23
CHAPTER 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 KΩmetal film resistor. After three seconds,
repeat Step d with the 10 K* 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.