Thermo Scientific 146i, Instruction Manual

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Preventive Maintenance
Monitoring Detector Frequency and Noise
5-4 Model 146 i Instruction Manual Thermo Fisher Scientific
3. Loosen the Allen screws (4) securing the photometer to the floor plate
( Figure 7-12 ) and remove the photometer.
4. Remove four (4) mounting screws on the lamp heater and remove the
heater.
5. Remove the lamp housing ( Figure 7-12 ) and the associated components.
6. Remove the detector. Refer to “Detector Replacement (Photometer
option)” on page 7-35 .
7. Remove the detector housing ( Figure 7-12 ) and the associated
components.
8. Push a piece of lens paper down the tube using a 1/4-inch piece of
Teflon® tubing so as not to damage the tube. Use a cotton swab to clean
the window surfaces through the holes that the tube fits into.
9. Replace the photometer components following the previous steps in
reverse.
Note It is recommended that the Model 146 i be recalibrated if the
photometer has been completely disassembled. Always check for leaks after
replacing any component. Refer to “Leak Test and Pump Checkout” in the
“Servicing” chapter.
10. Re-install the instrument cover.
Monitoring Detector
Frequency and Noise
The Model 146 i measures intensity ratios and not absolute values.
Therefore, a large range of detector frequencies are acceptable for proper
operation of the instrument. The nominal values are 65 to 120 kHz. These
frequencies can be monitored from the Intensity Check menu in the Service
menu.
The Intensity Check menu is used to manually control the flow of reference
or sample gas through the photometer. This enables the detector intensity
and noise reading to be determined with either reference or sample gas.