Automatic Calibration of a Shaw Dewpoint Meter

The most important and unique feature of the SHAW system is the automatic calibration facility. Each SHAW Dewpoint Sensor is precisely manufactured to saturate with water vapour at its design maximum. Hence, when the dew point sensor is exposed to moisture above its maximum operating range, it will rapidly come into equilibrium and cease to respond to any further increase in moisture. This forms the basis of automatic calibration (AutoCal). The SHAW dewpoint sensor can be checked by simply exposing it to any atmosphere which is wetter than the operating range of the dewpoint sensor (usually room air is sufficient) by raising the desiccant chamber and performing the AutoCal feature on the instrument. The dewpoint sensor is now set up with the instrument and ready for use. Automatic calibration of SHAW dewpoint instruments allows user to ensure accuracy between laboratory calibrations by checking the span of the hygrometer instrument and correcting for any deviation. Automatic calibration can be carried out in-situ and without the need for any special equipment or skilled personnel. The net result is reduced downtime, minimal calibration costs and immediate verification of the dewpoint system. AutoCal can be performed every two to three months but should not replace true calibration against a known standard.