Low cost pressure sensor

Hi! Lets be real. Worked with transducers ~25 years so what you want, although possible, is VERY difficult to arrange. Hence the prices. You define a range of 0-10bars (~ 10,000mm of water) with accuracy of

10mm, so you are on 0.1% measurable, repetitive level. Q. Do you have equipment to simulate those conditions for calibration purposes? Just a note, for this accuracy you need to take into consideration the barometric pressure at time of record, and it better be precise! So lets be real: Use overlapping ranges of transducers with ~1% accuracy. 10.000mm; 3000mm; 1000mm; 300mm and so on. It will be much more real. BTW, anything happened to proper glass tube and tape measure? Unconvenient, you also need a ladder but doable.

Good luck.

Stanislaw.

A cheap solution with a resolution of 1 in 10000 ????????? You better start saving money, because at that resolution you wil need a LOT of money. If you want to keep it cheap and skip some of that accuracy, make a closed box able to withstand your 10 bars, and use a plate inside near a slightly flexible side of the box, use it in an oscillator, and measure the frequency change. If you succeed, you have just made a capacitive pressure sensor. Solution 2: fill a pipe with a resistor chain,and reed relays to short the chain to ground at that place, then float a magnet outside the pipe, such that at least two reeds switch when the magnet is near. For protection you can fill up the pipe with tar, epoxy ,etc. This gives about 1 inch resolution,and is rather cheap. Solution 3: Buy a springloaded 10 turn potentiometer,and attatch a wire and float to that. The accurate ones are expensive, and at ten bar you have a level change of 100 meters (100+ YARDS).

10mm ain't going to be easy.

The problem with cheap pressure sensors is that they may not be temperature compensated, and that's bad news, especially if you are trying to achieve that sort of accuracy. To compensate a cheap pressure sensor can take a lot more effort than buying one that is already compensated - been there, done that, not easy.

I just installed a water level gauge in my rainwater tank, it uses a float on a string with a dial, works a treat. What is it you are really trying to do here?

Dave.

Well You see there`s a little problem with sensors/transducers which are capable to handle less than 5 bars. That problem is vandalism. I want to throw submersible water level data logger into the lake and forget about it for 6 months. Then I`m going to visit the site, get the data, change the battery and throw it to the depth again. If the data logger is somewhere in shallow water or near the coast line it may be stolen. So the solution is to keep it in quite deep place of the lake. Now I see that the bigger problem is to get such sensors/transducers which are needed for such application. So I`m thinking that maybe it is better that one or two data loggers are stolen than all of them are expensive and hard to find in such deep parts of lakes.

Actually yes. I have lots of stuff and very good conditions for creating, calibrating and using such data loggers but the one and only thing is money. I must use my own money and as I mentioned I`m a student so I don`t have lots of it.

The barometric pressure will be taken from nearby meteorological stations+short term meteorological models.

I think that`s what I`m going to do...I mean thanks for solution :) But maybe anyone could tell me some exact transducer model which could be good enough for, let`s say, 10 or 3 m?

The lake is 40-50km away from my native town, so going there everyday takes lots of time and fuel :) People living nearby the lake are not helping with this task.

Thank You

I know, I know. It sounds like mad science or stupid student, but I was still hoping that there are such good stuff and it doesn`t need lots of money wasted.

Thank You. This solution sounds very interesting and I think I`ll try this as an experiment next semester. Thanks again for such a good idea.

Hm...for short time level measurements this would be nice enough.

This solution is good too for shallow lakes. I think I`ll try this when I`ll have some stuff to do in little shallow lakes or ponds.

Yes. Other replyers already opened my eyes and now I know that 10mm with 10bars is practically impossible with cheap sensors.

Well. Temperature is not the problem as far as in more thant 10m depth of lakes it is quite stable.

If the amplitude of measurements would be less than it is now (1,5m, because of some heavy rain 200mm/24hours!!!) and there would be no threat of vandalism, this would be the perfect solution, but now it`s just useless for this application.

I`m trying to create a submersible water level logger for local lake level recording. And some lake levels are fluctuating 1,5m while others are just 5-15mm.

Put some ballast in your thing so that it stays upright, and put a waterproof ultrasonic sensor in the top, then just ping the surface.

Your signal will be very noisy (from waves and chop and such), but shouldn't be hard to average.

Good Luck! Rich

Where do you plan on putting the sensor? If you put it near the edge of the lake you could get away with a smaller range pressure sensor (say 1bar) and sit it in

Try Electrosense Technologies at

They have a differential pressure water level data logger for under US$250. Comes in a range of depths. 0-3 meters has precision of 3mm

Pete