Cheapest way to measure water depth

[yalew]

I am interested to measure the water depth in a tank above a reference point. The water depth or pressure varies above the reference point from 0 to 2.5 meters. How can this be done in a cheapest way without buying expensive piezometers and data loggers?

 

[logbook]

Without more data your question is essentially unanswerable.

Do you want remote electrical data or a big pointer on a stick which is read locally?

If remote do you want a continuous readout on a pc?
Is the pc local to the tank or miles away?

 

[danw2]

sight glass
connects to side of tank, liquid fills glass, look at the glass, see the liquid level, know the height.

 

[danw2]

Gems also has a yard stick on a float.

Dan

 

[OperaHouse]

Expensive is different to different people. Water has weight and you can measure the depth of water with a pressure gauge/sensor. In the same vein, a tube can be stuck in the water and air pressure can be applied to the tube. The prssure remains constant at the point where air bubbles out of the bottom of the tube. Great for liquids that are dirty. Often people don't need what they think they need.

 

[VEBill]

'Depth of water sensing':

http://www.eng-tips.com/viewthread.cfm?qid=58310

(257 replies...)

 

[Warpspeed]

Cheapest way would be a suitably long length of wood with depth graduations in the unit of choice.

 

[itsmoked]

Ah yes, the legendary "compendium": 'Depth of water sensing'

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[zeitghost]

"Ah yes, the legendary "compendium": 'Depth of water sensing' "



Shall we start again?

First bore your hole...

 

[richs]

I disagree with Warpspeed!

I suggest that a cord, with knots tied on it attached to
a mass with a density somewhat more than that of the
surrounding water be used. After insertion, an operator
can yell out something like:

"By the mark twain!"

Where is your sense of history for Gosh sake! Besides,
have you priced wood lately?

Cheers,

Rich S.

 

[itsmoked]

Excellent point Rich!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Warpspeed]

Zounds !!

Beaten once more by a superior intellect.

 

[itsmoked]

Beaten or garroted?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[richs]

You guys must be speaking about Keith!

BTW, I'll have the applications page with the PLC on
it on my server in the next day or two Keith. Due credit
to you too!

Sorry, this is a little off topic.

Cheers,

Rich S.

 

[itsmoked]

Staying off track since the OP is missing in action.
Rich, That your SingleChipPLC?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[yalew]

I would like to thank you all of you for your reply. BTW I have gone through the "big" discussion about water depth sensing in this forum ....

http://www.eng-tips.com/viewthread.cfm?qid=58310.

After going through every post with a lot of pain ... I really couldn't find what I want ... that's why I posted it again.

The tank is inside a laboratory and the pressure varies in every 5 or 10 minutes during the experimental set up. The experment can run for 1 day. Obviously a man standing and recording the pressure variation is not a reasonable solution .. if the experiment is repeated for a lot of time.

Regarding the reading, it is continuous and I prefer the data to be saved and downloaded latter to my pc. If this is not alternative, It is also good to connect the pc to the measuring device continuously and record it at every time.

I want an automated and cheapest way to carry out this duty. From my search so far the pressure sensors are preferrable but when I check the price really it is not affordable for me. Can anyone suggest me a solution please.

Thanks in advance for every contribution!

 

[OperaHouse]

While you could spend a lot, I don't see an acceptable pressure sensor and data logger costing more than $150. Is this what you call expensive?

 

[BrianG]

I don't think you are going about this the right way: nowhere have you mentioned the accuracy to which you must know the depth of water - at the very least doesn't the tank have an ordinary ball valve to control the water level? .

You say you want to automate the logging of the readings: if this is such an important parameter which must be understood (and probably controlled at some point)then how can you afford not to make accurate measurements by using the appropriate sensors? Either it is important to whatever experiment you are conducting or it really isn't!

 

[felixc]

You take a Pentium-based PC onto which you attach a solid aluminum bar as a heat sink, one end at the top of the Pentium chip. You suspend the PC until the tip of the aluminum bar reaches the lowest measurable point. Water acting as a heat drain, the higher the water goes the cooler the Pentium becomes. With your monitor at the top of the hole, you go into the BIOS and measure the temperature of the Pentium. Then you use a videocamera to record the data. Hey where's my price for the latest application of a Pentium?

But seriously, what is your budget? There are stainless steel pressure sensors out there for $100. You will spend much more in your time spent writing your test procedure.

 

[richs]

O.K. To get serious here.

There are a lot of pressure transducers out on the market
for 0-7 psi. Some are available from I believe Jameco
for 0-1.45 psi. These are all in the under $20.00 range
and I believe are used for automotive applications. Large
volume ==> low price. Usually they don't have very
robust enclosures, but that might not be the issue.

Piece together the following link:

http://www.jameco.com/webapp/wcs/st...1&catalogId=10001&langId=-1&categoryId=352540

Someone earlier mentioned a "bubbler" method of doing
depth of tank monitoring. This requires a low pressure outside air source. One might be interested in looking
at deep tank aquarium air pumps.

A small needle valve can be placed at the output of the
air pump. This feeds a "tee" connector which has a
tube to the bottom of the tank (or the lowest pressure
that one wants to measure). The other side of the
tee goes to the inlet of the pressure sensor. The
valve is adjusted until there is a small stream of
bubbles (hence the name) coming out of the tube on the
bottom of the tank with the tank full.

The amount of pressure on the inlet to the pressure sensor
will be proportional to the depth of the fluid in the
tank. Excess pressure from the air supply will come out
the bottom. So, there will be a greater pressure with
the tank full vs. when the tank is empty.

The bubbler does NOT take into account the density of
the fluid, therefore, if you are changing the components
or concentration of the fluid, a variance will be
observed when tank levels remain the same. This usually
isn't much of a problem in many applications.

Feed the output of the transducer into a suitable
insturmentation amplifier, then to an A to D converter.

The suggestion of using a PC is a pretty good one. One
can easily find A/D converter boards for the computer
along with suitable MATHLAB type software.

MPJA has some low cost 0-7PSI sensors available for
under $5.00 however, I had to build an enclosure for
it. The inlet is a bare hole.

I have two versions that I used:
1. I epoxied a "nipple" from a water drip system onto
an ordinary water faucet washer. I then *CAREFULLY*
epoxied the assembly to the pressure transducer, making
sure that I did not plug the hole.
2. Turned an aluminum enclosure for the transducer with
my lathe. Much more robust..... Turned that $5.00
sucker into a $100.00 type.

OPPS! I see MPJA is out of them. Well, it is a surplus
house..

Hope the other stuff helps.

Cheers,

Rich S.