Quote Originally Posted by CescoAiel View Post
True, but it does seem a reliable measurement can be gotten that way. Possibly by submerging the sensor in the fluid, we could get better results (measuring delta is more important than the absolute level here. We can give it a one-time offset to compensate for the measurement difference too, so the absolute is corrected)
At a previous job I built robots that used the Olympus ultrasonic thickness sensor to detect the thickness of metal plates. It needs a layer of water between the probe and the plate to achieve a good reading. I am not sure about corrosion although most of the probe is anodised metal. The end of the probe is also about the size of a dime.