rick@cadtec.UUCP (Rick Auricchio) (04/27/85)
--------
[]
I think the ultrasonic thing is out. Remember, he said he's using a
*submersible* pump, which usually means that the water level is quite deep
(say, >150 feet down). The transducer probably won't do at all, especially
since the well casing is metal.
Several (must be 15-20) years ago we had a well with a submersible pump. I
seem to recall it being 330ft deep, with a "static level" (water level) of
about 180ft. This level was tested with a wired probe. The probe, being
lowered by hand, didn't hurt the pump, but then the pump wasn't running.
I recall the well guys could also determine flow rate of the well by seeing
how fast you could draw water (with the pump running) before the static level
dropped. Might be worth asking a well company for info on this.
Echoes, by the way, were spectacular. Unfortunately, there were dozens of
repeats so I think even the speaker idea is a loss.
==============================================================================
Opinions expressed have been generated solely by line-noise.
{cbosgd,decwrl,hplabs,ihnp4,seismo}!nsc!cadtec!rick N1150G (408) 942-1535
"The sooner you fall behind, the more time you'll have to catch up!"swift@reed.UUCP (Theodore Swift) (05/04/85)
For something that's going to be 150' down, the Polaroid rangefinder is definitely out. Have you considered using a solid state strain- gauge? I've just finished a thesis which uses two of the suckers to measure water level in a recording tide gauge. SenSym in Santa Clara (a spinoff of Nat'l Semiconductor) makes all kinds, starting at about $20.00. The ones I used act like Wheatstone bridges, giving an differential output voltage proportional to pressure*excitation voltage. You could put a sensor and a differential amp at the end of a four-strand cable and drop it down the pipe (two strands for +-power, one ground, one single-ended analog output voltage). Upstairs you could read the voltage with a normal VOM or, better yet, have a similar p-sensor/amp circuit reading barometric pressure and subtract air from air-plus-water pressure either digitally or analog. A cheap/semi-accurate way of going digital would be to hang a voltage-to-freq converter chip off of the diffamp downstairs, then use a freq counter upstairs (set the V/F converter to some appropriate range. SenSym makes gauges in all sorts of pressure ranges for all sorts of benevolent and malevolent environments (for a price..) in three basic flavors: absolute (refered to vacuum inside sensor), differential (two pressure ports read difference in two pressures) and gauge (pressure at port refered to ambient air pressure around sensor). A good discussion of the idea can be found in "Build a Solid-State Barometer" by Gupta in _Radio Electronics_, around June, 1984. An even better discussion can be found in _the Pressure Sensor Handbook_, Sensym Corp, Santa Clara, Ca. (sorry I don't have the address/phone) They sent me a copy without extracting a promise to order 10,000 units with little or no hesitation. I apologize if I didn't present the basic idea clearly. There are lots of different ways of doing it. Oh yeah: I guess I should say this: I have no connection to SenSym, NS, RE, or any other individual or corporation mentioned in the above text, other than having bought two 06030 absolute sensors (0-30psi) from SenSym, and having read Mr. Gupta's article in RE. Happy dousing...