Characterization of a SAW-Pirani vacuum sensor for two different operating modes

This paper introduces latest results achieved with a Surface Acoustic Wave thermal sensor for vacuum measurements, namely a SAW-Pirani vacuum sensor. The principle of the sensor is described and its pressure range [10(-3) Pa - atmospheric pressure] is compared to the state of the art. The fabrication process is described as well as the sensor integration on a printed circuit board. The SAW device is a delay line with a frequency response centered at 433 MHz. Its thermal behavior has been characterized in order to determine the sensor temperature so that it works in its optimal temperature range. A specific test bench has been developed to perform the characterization of the sensor in terms of pressure response and response time. With this test bench, two possible operating modes have been assessed in terms of sensitivity and response time. It has been shown that selecting the appropriate operating mode of the sensor can lead to divide by a factor of 60 its response time. Finally, the detection limit of the sensor has been measured and its repeatability has been assessed. (C) 2012 Elsevier B.V. All rights reserved.