6-16
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6.4 Maintaining the Detector
This section provides procedures for replacing the deuterium lamp in the absorbance detector.
The procedure include:
•
Removing the old lamp
•
Installing the new lamp
•
Adjusting the lamp position
Lamp Characteristics
The intensity of the deuterium source lamp varies by wavelength (Figure 6-13).
Figure 6-13 Deuterium Lamp Intensity Profile
When to Replace the Lamp
Performance requirements and permitted tolerances vary from application to application. If the
lamp no longer provides an adequate signal-to-noise ratio for your application, replace it.
It is not unusual for lamps to show a 30 to 50 percent decrease in intensity before the noise
increases by a factor of two.
Lamp Timer
The detector lamp has a life of approximately 1000 hours. One of the leads attached to the lamp
includes a 1000-hour timer to indicate lamp usage.
Before you replace the lamp, check the lamp timer (see Figure 6-14).
The lamp timer is a mercury column with a scale of 0 to 10 where 10 represents 1000 hours. As
the lamp ages, the bubble in the mercury column moves toward the 10.
Relative
Intensity
(%)
Wavelength
(nanometers)
190
656
100
50
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