Dew Point Meter Model LPDT

Electronics

The compact LPDT dew point meter is a fully functional instrument operated through a miniature custom LCD display and three push buttons, using the same user friendly interface of all Xentaur hygrometers.

The analog output is linear to the engineering units selected for display and is user configurable. A weatherproof cap is available for outdoor NEMA 4X (IP65) applications.

Sensor

The model LPDT uses a Xentaur HTF™ Aluminum Oxide sensor. The breakthrough HTF™ sensor technology represents advances in thin film and metal oxide sciences and other 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.

High Capacitance Response

HTF sensors have a capacitance change, several orders of magnitude larger than that of conventional aluminum oxide sensors due to the hyper thin film, a sharp transition layer and a special pore geometry. Additionally, this change is quasi linear and its sensitivity to temperature is negligible. The advantages of a linear high capacitance response are: better sensitivity, better repeatability and faster response times. Also, the measurement system is less prone to noise and drift, and signal conditioning is kept to a minimum.