Preventive Maintenance

Nitrogen-phosphorus detector (NPD)

Turn off the detector and its heated zone; also turn off gases to the detector (particularly H1! ). Allow time for the detector zone to cool. Open the top cover at its front edge to access the detector.

1.Using a Pozidriv•typescrewdriver, remove three screws around the detector cover and carefully remove the cover (see Caution below).

Caution Note that the transformer supplying power to the active element is secured to the inside of the cover. It may be left in place, but be careful not to stress its leads, either those to the collector, or those to the detector signal board.

Figure 8-15

NPD Collector Assembly

Active Element

Active Element Transformer

NPD Collector and Active Element Power Supply Transformer

WARNING Wear proper eye protection when using compressed gas for cleaning purposes.

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