15.4 Replacing the Photomultiplier
15.4.1 Overview of Replacement Procedure
Follow the procedure below to replace the photomultiplier.
Use the existing photomultiplier to measure the peak value of the Raman spectrum of water (F
value).
Replace the photomultiplier.
Calibrate the wavelength.
Compensate the sensitivity using peak height of the Raman spectrum of water.
15.4.2 Pre-Replacement Procedure (recording the peak value of the Raman spectrum
of water)
Before replacing the photomultiplier, fill the cell with water and check the S/N ratio in validation
mode. Then record the peak value and EM wavelength of the Raman spectrum of water (F
value) for the existing photomultiplier.
This peak value (F value) will be used as the target value for compensating sensitivity after
replacement.
Example: F value of 50 (as a general guideline, this should be between 30 and 100)
EM of 397nm
15.4.3 Photomultiplier Replacement Procedure
(1) Tilt the instrument over on its side, remove the two M4 truss screws indicated below,
then remove the bottom cover.
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