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T
ROUBLESHOOTING
5-6
October 1999 Rosemount Analytical 748250-L
Model 880A Non-Dispersive Infrared Analyzer
WARNING: BURN HAZARD
5.7 SOURCE ALIGNMENT
Note:
These adjustments are part of the factory checkout, are not normally required
for routine operation, and should be done only if the detector signal obtained at
the end of Step 5, above, is greater than 1.2V.
The source housing is very hot. Ensure adequate measures are taken to avoid
touching this component during this procedure.
Before doing this procedure, balance the source as outlined in Section 5.6. Then do
the following:
1. Connect a digital voltmeter between TP6 and TP2 on the signal board.
2. Refer to Figure 6-2. Set the source adjustment screw so that ½” of screw threads
are visible (about halfway screwed in).
3. Loosen the two screws holding each source in place.
4. Adjust both measurement and reference sources up or down to reach the
minimum detector signal.
5. Re-tighten source housing screws.
6. Do the Source Balance procedure in Section 5.6.
5.8 SOURCE CURRENT ADJUSTMENT
1. Follow the steps in Figure 3-7 to access the Source Current display.
2. Refer to Figure 3-1. Adjust the trim potentiometer (R9) located on the Power
Supply Board to view the desired current on the digital display until the value on
the display is within
±
10 of the value on the application data sheet. Clockwise
adjustment of R9 will increase the value. Counterclockwise will decrease the
value.
5.9 CASE HEATER TEMPERATURE CONTROL
Refer to Figures 7-1 and 7-2. Malfunction in this option can occur in three sections:
Heater
- Check with an ohmmeter for continuity. The heater resistance is
approximately 113 ohms at 25
°
C.
Temperature Sensor
- This is an RTD and should have approximately 550 ohms at
25
°
C. Check with ohmmeter for continuity.
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