Operating Principle
The Xentaur dew point meter, XPDM utilizes HTF^TM aluminum oxide sensors which adsorb water molecules much faster than they desorb water molecules. It is therefore an advantage, if at the beginning of the measurement the dew point sensor is dryer than the gas sample to be measured. The XPDM dew point meter keeps the sensor in dry storage until the measurement is taken. The sensor slides directly from the dry storage into the sample cell, without ever coming in contact with ambient air. After the measurement is completed, the sensor slides back into the dry storage, where it is dried down for the next sample.

SpanCheck™  Without Reference Standards
Xentaur HTF™ high capacitance sensors have a very low residual capacitance when dry and saturate at a predesigned level of humidity above +20ºC (+68ºF). This allows a SpanCheck™ of the sensor by exposing the sensor to a saturated environment for one minute and adjusting the instrument to its upper range limit. It is preferred that the customer use a known gas to determine the saturated environment.

The advantages of this SpanCheck™ system are obvious: Xentaur dew point sensors can be field calibrated anywhere and anytime. Sensors do not have to be returned to the factory for recalibration, which also eliminates the need for a second stand-by sensor.

Xentaur Hyper-Thin-Film (HTF) AL2O3™ Moisture Sensor Technology
The model XDT uses a Xentaur HTF™ Aluminum Oxide sensor. The breakthrough HTF™ sensor technology represents advances in thin film and metal oxide sciences and offers significant performance advantages over all other aluminum oxide sensors.The operating principle of the HTF™ aluminum oxide sensors is that a hygroscopic layer of aluminum oxide adsorbs or releases water molecules within its pores, depending on the water vapor pressure in its environment. The electrical capacitance of the aluminum oxide layer changes with the surrounding water vapor pressure. The electrical capacitance is measured between the aluminum core of the sensor and a porous conductive gold layer on the outside.The advantages of the HTF sensor technology are a result of the proprietary manufacturing method in which the aluminum oxide layer is made to be hyper thin as well as extremely hygroscopic. This results in a very sensitive sensor with fast response.