Humidity Calibration Using Portable Relative Humidity Generators

Chilled mirror placed inside of RH calibration chamber through an access port on the chamber door.

by Michael Boetzkes

Not too long ago, the RH calibration chambers which were appropriate for calibrating the high accuracy RH transmitters were limited to custom build chambers at the sensor manufacturer and a very small handful of commercially available units, none of which could be considered portable. As happens with all technologies, Relative Humidity generators have been developed and improved, reducing their size and making improvements to measurement uncertainties. When using the standard control sensors, these portable systems will often have uncertainties larger than laboratory based RH generators; however, these portable systems can often be improved upon by using external temperature and RH references.

This paper will explore some of the key features which differentiate the different portable RH generators as well as look at examples of the uncertainty budgets for two systems, a portable generator using the internal sensors and the same generator using external references. Read Full Article (PDF)