Check out our website www.senix.com We make ultrasonic sensors that provide analog outputs and/or RS232 outputs. Senix Corporation 52 Maple Street Bristol, VT 05443 1-800-67-SENIX ---------- > From: Timothy D. Gray > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: Measuring stuff with PICs > Date: Wednesday, June 24, 1998 7:29 AM > > You can bounce an ultrasonic wave at it without a pipe, or use an air > bubbler and measure the air pressure change, use a float attached to a > string and a variable resistance, use 2 stainless steel electrodes (Highly > inaccurate as condictivity of water varies greatly in a river), there are > thousands of ways to measure fluid level, check out an industrial catalog > of sensors. > > On Wed, 24 Jun 1998, James Cameron wrote: > > > Tjaart van der Walt wrote: > > > How does one measure a river's water level (2.5m change) without > > > little contacts that will corrode? > > > > Use little contacts that will not corrode. Keep them at identical > > potential for most of the time and only raise them to make measurements, > > or place a sacrificial anode nearby and keep the contacts at least a > > little bit on the "right" side of the anode. > > > > > My idea is to put a vertical pipe with a hole in the > > > bottom into the water. A speaker (with a plastic > > > cone) is placed at the top of the pipe and the [...] > > > > Hmm. Never thought of peak frequency measurement. I'd simply bounce a > > pulse down the tube and recognise the peak return. Time for the bounce > > is distance. > > > > > BTW what sort of a sensor would be able to measure > > > barometric pressure? > > > > Pass. Last I checked it was expensive. > > > > -- > > James Cameron (james.cameron@digital.com) > > Digital Equipment Corporation (Australia) Pty. Ltd. A.C.N. 000 446 800 > >