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Teledyne API Model 200AU NO
X
Analyzer Instruction Manual, 02293, Rev. F
9-46
In addition there is a thermocouple amplifier for the Moly converter.
Thermistor Temperature Amplifier Adjustments
If the temperature readouts are in error:
1. Locate the Box temp thermistor on the board and place a calibrated thermometer near the
thermistor.
2. Select the BOX TEMP - TEST function on the front panel.
3. Adjust R34 until the front panel readout matches the thermometer readout. This will
cause all of the readouts to accurately measure their respective temperatures.
Molybdenum Converter Thermocouple Amplifier Adjustments
The molybdenum converter temperature is sensed by a thermocouple. The cold junction
compensation and signal conditioning is done on the Temp/Status board.
The buffer amplifier from the thermocouple amplifier to the CPU for the Moly temperature has a
gain adjustment. The voltage times 100 at pins 8-9 of U1 is the Moly temperature in degrees C.
For example 3.15 VDC at pin 9 of U1 is 315
o
C. The CPU is programmed to always drive the
temp to 315
°
C, so the voltage at U1 must be used as the absolute reference as to the correct
temperature. The temperature will vary
±
3 degrees due to the operation of the temperature
control loop in the CPU.
The R6 pot on the Status/Temp board can adjust the temperature. To adjust the molybdenum
converter temperature:
1. Select the CONV TEMP - TEST function on the front panel.
2. Wait until the converter is up to temperature, usually 30-45 min after a cold start.
3. Adjust R6 until the voltage at pin 8-9 of U1 is 3.15 VDC. The CONV TEMP - TEST
function will then read 315
°
C.
4. Recheck the temperature 15 min later and re-adjust if necessary.
9.3.4.2 Display Brownout
During low AC line conditions the display can lock up due to insufficient voltage. When low
line conditions are approaching, this circuit senses the condition by monitoring the un-regulated
+5 VDC in the Power Supply Module. If brownout conditions are met, the DISP_BROWNOUT
line is asserted and the CPU sends a hardware RESET command to the display and sends a
BRNOUT RESET pulse back to U4. Brownout conditions will be noticed by the display flashing
every 8 seconds.