Yokogawa GD40 Gas Density Detector - Manual (Page 52)

<3. Operation>
3-9
IM 11T3E1-01E
3.2.3 Inspection and Maintenance
Due to the operating principle (polymodal self-excited oscillation circuitry), the sensor has only
the slightest marginal drift, which is, in fact, generated by the detector itself or a result of contami-
nation from dust, etc. Therefore, the GD402 analyzer basically does not have to undergo any
inspection or maintenance. Periodical inspection and maintenance are recommended however,
to ensure optimum performance. For details on inspection and maintenance, see Chapter 11.
3.3 Shutdown and Restart
3.3.1 Measures for Shutdown
Data set in the converter are retained even when the power is turned off. If the system needs to
be shut down over a prolonged period, turn off the power. Any foreign matter that accumulates
and hardens on the detector or any corrosive substance that condenses on the detector can be
the cause of problems. Fully purge the sensor with fresh air (instrument air). Cleaning of the sen-
sor is also recommended where it is appropriate; consult Yokogawa.
3.3.2 Measures for Restarting
Visually check all component equipment of the analyzer before you resume measurement after a
long-term shutdown of the analyzer. Re-confirm the wiring and piping have tight connections .