Oilresistant ultrasonic sensors
Ultrasonic transducers are the heart of ultrasonic sensors. They are basically a microphone and speaker for high-frequency sound waves. As with audio speakers the diaphragm should be able to move freely. On an ultrasonic sensor this movement is only a few micrometers. Therefore it needs a flexible mount but as well a good seal between the white matching layer and the housing.
Different manufacturers use different seal materials such as silicone, polyurethane foam or rubber. SNT Sensortechnik AG uses as an innovation seals made of FPM (Viton®). This is a fluoroelastomer with very high thermal and chemical resistance. Unlike other elastomers, it withstands hydrocarbons such as oils and fuels also at higher temperatures and it does not swell or dissolve. It is resistant against acids and alkalis as well. And yet it is still elastic.
Thanks to the new seal, ultrasonic sensors from Sensortechnik AG are now more resistant to chemicals, especially to oil – and this without impairing the currently achieved high detection sensitivity.