Section 11
Model 601/601P/602/602P/603 NDIR Analyzer
California Analytical Model 600_NDIR_Series_v10.0 CE
Operators Manual
Page 70 of 86
11.5. Check and Repair Infrared Light Source Unit
(No. 5 in Figure 10-1)
11.5.1. Problem:
A faulty infrared light source or a leaky gas seal.
11.5.2. Symptom:
The unit reads off scale or the output is unstable.
11.5.3.
Check and/or replace:
1)
After turning the power switch to OFF and disconnecting the lead wires from the
two terminal screws, measure the resistance between the two terminals. The
resistance should normally be about 38 ohms. If the resistance is infinite, the
infrared light source is faulty (Output drifts in the negative direction as resistance
decreases).
2)
When indicator output drifts due to influence from atmosphere in spite of normal
operations of the detector and main circuit board, gas may be leaking into the
infrared light source unit.
Note: In the case of a low-concentration CO
2
analyzer, the indicator output may
fluctuate due to atmospheric CO
2
penetrating the gaps in the optical bench. This would
be normal and not necessarily indicative of a problem. Purge the analyzer case with N
2
gas.
3)
Replacement: After disconnecting wires from the two terminal screws and motor
connector, remove the two screws that are used to attach the infrared light
source unit to the optical bench. The light source assembly can be replaced,
referring to Figure 10-1 or Figure 10-2.
4)
After replacement of the infrared light source unit, adjust the zero level and span.
11.6.
Check and Replace Chopper
(See Figure 2-1)
11.6.1. Problem:
Rotation abnormal.
11.6.2. Symptom:
Indicator output unstable or unresponsive.
11.6.3.
Check and/or replace:
1)
With the power switch turned ON, listen for a frictional noise from the chopper
blade. If noise can be heard, it is necessary to adjust the chopper blade so that
no contact is made with other parts. Remove the infrared light source assembly
and detach the protective cover for access to the chopper blade. Take care not
to damage the blade, as it is made of thin material. No adjustment is required as
long as the output is normal.
2)
If the motor shaft does not rotate after energizing the instrument, disconnect the
power supply connector from the motor and check to see if AC 100 Volts is
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