Low-power non-invasive flowmeter

[olefrt]

Does anybody know of any low-power (i.e. battery-operated) non-invasive flowmeters, suitable for measuring flow of "dirty" water (such as waste water, that may contain debris, possibly including strings etc.)? I've looked at mag meters and ultrasonic meters, but what I've found so far is way too power-hungry and/or "fragile". Meanwhile, common turbine meters and various types of positive-displacement meters are all "out" because of debris in the water that would instantly clog and/or damage the mechanism. This meter may be used in remote locations where no A-C power is available. Long battery lifetime is a must, and accuracy has to be better than differential-pressure and similar types! Typical would be a 2-inch application, with a flowrate of approximately 30 - 40 GPM. Of course price is important too, but at this point I'm open to any suggestions! (Full disclosure: I'm a design engineer for a company that makes flowmeters. I've been tasked with proposing a design for such an animal.) Thanks.

 

[zdas04]

I'm very interested in your statement

and accuracy has to be better than differential-pressure and similar types!

I especially find the exclamation point interesting.

Getting past your choice of punctuation, I have a couple of problems with the quote. First, I find it very telling that someone charged with designing a flow meter would use the horrible term "accuracy". Since it doesn't mean anything it is really hard to use the term in a design. In measurement we use the terms "uncertainty" and "repeatability" to encompass the concepts implied by the word "accuracy". Second, I can get +/-0.5% uncertainty with excellent repeatability with a V-cone meter and a digital dP gauge. I can't imagine another technology that will be significantly better than that, certainly not with your power constraints.

Without the power constraints you could do a pair of weigh-scales, but everything else I can think of would have problems with the strings (and I'm not sure I could select a diverting valve that wouldn't also have that trouble).

David

 

[StoneCold]

I think that if you don't go with zdas04 suggestion, which I think is good then you should go with the mag meter and solar power with batteries to get your readings. I did not even imply that that was the cheapest option, but it does beat a small nuclear reactor which was my second choice.

Regards
StoneCold

 

[stanier]

Why not use a solar array to provide power?

Alternative devices could be coriolis, vibrating wire or three thermocouple type but I have no idea as to power usage.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[amorrison]

Consider dutycycling your meter. A reading (a meter turn on) for 0.1 seconds in a 10 second cycle gives a duty cycle of 1%. Maybe your batteries could "handle" the 1% for some "time".