We have a 500-gallon outside propane tank. It's maybe 30 feet from the house. It has a gauge on top, under an armored cover, but the tank is frequently on the far side of (and frequently covered in) significant amounts of snow.
Does anyone happen to know of, or have any suggestions for, a way I can remotely monitor the level of propane in the tank? Obviously anything that would involve retrofitting a sensor of some kind inside the tank is pretty much out.
Edited to add: I need to get data back in a form that can just be logged and charted automatically 24 hours a day, preferably without having to do image recognition on webcam images of the gauge.
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He said that the gauge is on the wrong side of the tank... and frequently covered in snow. What about a small roof for the tank, and well placed mirrors so that the location/orientation of the gauge isn't a problem, and it doesn't get covered in snow?
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Not having much joy looking for anything on how it works.
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Tank level
The other option is that the guage on the outside is presumably a pressure guage. I'd imagine it should be possible to purchase a pressure guage with electronic output at some (probably non-trivial) expense. It does require ensuring the tank is then pressure sealed again, which simply sitting the tank on scales doesn't.
Ewen
PS: Given more convenient weather conditions I believe one can observe the levels from the outside by the proportion of condensation on the outside of the tank. But lack of convenient weather conditions seems to be a major sticking point here...
Re: Tank level
Re: Tank level
The volume of gas contained within the tank will vary according to local temperature, but that's easily determined from Boyle's Law once you have the contents determined.
A piezoelectric weight gauge is, IMHO, the best option here.
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[Thought] Is it possible to introduce a radio signal? There may be a frequency that propane liquid is opaque to. The chamber should have a resonant frequency based on the gas chamber volume.
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Density of snow: 50-150kg/m^3
The relative densities are such that it will take a lot of snow to throw off the calculations by an appreciable amount.
You can also take the weight of the snow into account. Look at how much the tank weighed before the blizzard, then look at how much it weighed after the blizzard. The difference will be a fairly good approximation of the weight of the snow on the tank, which can then be factored into ongoing calculations.
Piezo is simple, effective, and accurate enough. It's still the one to beat, IMO.
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Would it be possible to measure under just one anchor point?
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I sympathize with you on your within-5% instincts. It's an excellent ideal to live up to. In this case, though, we can live with 50% experimental error. If
I think it's possible to measure under one anchor point, yes, esp. if it's done under the geometric center of mass.
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(1) Get an actual metric for the rate we're using propane in various combinations of use
(2) When the delivery slip says 300 gallons, be able to verify that the driver really did put 300 gallons in.
Apparently a previous delivery driver in this area was caught over-billing customers and putting the excess propane into his own tank. He got free propane, while the customers on his route paid for propane they weren't getting.
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Another approach I thought about is using an ultrasonic transducer to measure the depth of liquid in the tank, either from the top or from the bottom. In principle, I should be able to bounce a ping off the liquid-gas interface and, again, determine calibration points relative to the gauge.
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Unless the whole thing sits on a slab.
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These tend to get a little fuzzy as the tank level gets very low, but you'd have historical data to look at to determine that your tank was actually low as opposed to the fuzzy data being due to equipment malfunction.
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