Moisture/Dew Point Analyzers

This chapter describes the methods and technologies for selective moisture detection at trace levels. Moisture values are expressed as units of pressure, dew point, frost point, or calculated values incorporating independent parameters. Important mathematical relationships are presented to aid in understanding certain applications and the behavior of hygrometers for process analysis. The electronic versions of the dew cup automate the performance of the condensation experiment. Manufacturers of hygrometers maintain calibration laboratories that can provide certification of traceability to the National Institute of Standards and Technology for their instruments and probes. Field calibration systems find greater application to validation of hygrometer performance. A sampling system incorporating a filter/coalescer is needed to protect the hygrometer sensor in most industrial dryer applications. Hygrometry of natural gas is nonideal at low pressures and includes special problems of contamination.