Ametek CEM/Humox, Руководство пользователя

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6-10 | Thermox CEM/Humox Analyzer
Thermocouple compensation circuit check
With a volt meter, measure across terminals 2 (-) and 12 (+) on the sensor board. If
approximately 15 volts is not present, check that interconnecting wiring is correct.
If interconnecting wiring is correct, check across 15V Sup and 15V Com on the
control unit for approximately 15 volts. If 15 volts is not present, check fuse F1 on
the wiring card. If this fuse is OK, replace the control unit power supply/keypad
module. If this fuse is not OK, replace the fuse (1/4 amp, 125 volts, IEC speed type
FF). Check the interconnecting wiring for short circuits before applying power to
the control unit.
If you do measure 15 volts at terminals 2 (-) and 12 (+) of the sensor board, mea-
sure across terminals D (+) and 6 (-) on the sensor board. Twelve millivolts should
be measured (this signal is a function of ambient temperature and may vary up to
2 millivolts at extreme ambient temperatures). If you don’t measure this voltage,
replace the sensor board.
For a furnace temperature set point for a 615°C oxygen cell temperature, the furnace
thermocouple output would be about 27 mVs (take memory location 88 which is
the T/C Ratio calculated during the primary - thermal calibration and divide the
cell temperature by this value to come up with the furnace temperature set point).
Note: The cell thermocouple compensation circuit on the 80471SE,
80485SE, 80467SE and 80505SE sensor boards is different in comparison
to the 80418SE sensor board that was supplied with Series 2000 based
systems prior to 1996 (CE Marked Systems).
The 80418SE used the 40.2-ohm resistor on the display module to sense
the current sourced from the AD592. The compensation current produces
a voltage drop across the resistor on the display module and then adds this
voltage to the raw T/C mVs sensed at the T/C + and - connections at the
wiring board and at the sensor board.
The change was implemented on later sensor board designs (80471SE,
80485SE, 80467 SE and 80505SE) due to the confusion caused by seeing
a display that was approximately 12 mVs higher than the voltage measured
at the terminals on the wiring board.