Wanted: Twin Wire Resistance Wave Gauge

is this in salt or fresh water or in between?

The conductivity of the fluid is important.

if you use a stainless steel resistance wire that is chosen to not corrode in the fluid and has the correct resistance the problem can be solved. If you have a flume of metal you can get away with a single wire and you calibrate it to the fluid (bearing in mind the enormously different resistance you will need for fresh/salt water since salt water is very conductive). With no metal flume, a 2 wire gage measures the resistance as it varies from low water = high resistance, to high water = low resistance.

a simple search gives this, which includes this thread, but has some useful references.

http://www.google.ca/#hl=en&source=hp&q=%22twin+wire%22+%2B%22wave+gauge%22&btnG=Google+Search&meta=&aq=f&oq=%22twin+wire%22+%2B%22wave+gauge%22&fp=fdb7627fc4f0229c

I agree that the design may be fairly simple. Is the wave tank using seawater or fresh? Is an ultrasonic distance sensor a possible alternative? If so, see: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf

You might get some help from Onset Computer, mfr of the Hobo and other dataloggers: http://www.onsetcomp.com/water-level-logger

Here is a twin wire manometer that meets your spec but looks like it may be costly: http://www.discoverarmfield.armfieldonline.com/data/h40/?js=enabled

thank you.

I was able to get a quote from two companies ( one of the m armfield) and it is expensive. i will try to look for some alternatives maybe submersible mini pressure transducers or something until i get something reliable and within my price range.

thank you for your contributions.

Cheers!

Ram.