A Microflown based sound pressure microphone suitable for harsh environments

There are several cases where a sound field reconstruction or prediction is required under harsh conditions such as high temperature, humidity or chemical attack. A regular pressure microphone won't last long under these conditions. Electret based pressure microphones stop working well above 70 degrees centigrade and other types of pressure microphones often operate with a built in amplifier that does not function above 120 degrees centigrade. The functionality of a MEMS based microflown acoustic particle velocity sensor in air lies in the use of two heated platinum wires that are resistant to high temperatures and chemical attack. The wires are supported by silicon that has no other function than provide mechanical support. A pressure microphone is made based upon the particle velocity principle by putting a microflown inside the opening of an enclosure. In this paper a sound probe for harsh environments is created, combining particle velocity and pressure measurements in a harsh environment. Use of this sensor is possible up to 250 degrees centigrade, in humid and under most chemical environments. The probe realization as well as calibration measurements are presented.