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Topic: Pressure sensor for truck's water tank (Read 503 times) previous topic - next topic

ma13

Hello!

I'm doing a project that aims to provide information on the water filling level of a truck tank.
After reflection I chose to go to a pressure measurement at the bottom of the tank which, with a bit of fluids static, will give me the height of water in the tank.

But I have a small problem for the choice of my pressure sensor .. I think I need an absolute pressure sensor because it will be completely immersed.
It also must be waterproof (for connections I will solve the problem with a little bit of resin).
Finally I would like it to be not too complicated to use, basically that I can find enough info (tutorial etc) for not having to look at the documentation.

My research always leads me to barometric sensors type BMP280 but I have doubts about their ability to dive into my tanks ...

Would someone have a reference to advise me?

(sorry for my english i'm french, but french people don't seem interested by my question so i try with anglophone ones)

jremington

#1
Feb 06, 2018, 12:21 am Last Edit: Feb 06, 2018, 12:21 am by jremington
Why does your sensor need to be immersed?

A gauge (relative) pressure sensor will work fine if you can connect it to the tank outlet. The only drawback with such a connection is that the readings will be too low if water is flowing past the sensor during the measurement.

ma13

My goal being to get the water level in the tank through the pressure that the water column exerts at the bottom of the tank, I do not understand how a sensor that does not undergo the pressure of the water could bring the information I am looking for. Can you explain to me how you would like to proceed?

Thanks for your help!

Wawa

A submerged/gauge sensor also needs a barometric sensor to compensate for atmospheric pressure changes.
A differential sensor (two ports) doesn't need that.
Leo..

jremington

#4
Feb 06, 2018, 02:17 am Last Edit: Feb 06, 2018, 02:25 am by jremington
Quote
I do not understand how a sensor that does not undergo the pressure of the water could bring the information I am looking for.
Of course the sensor must be in contact with the water column. A differential sensor connected to the tank outlet, before the shutoff valve, will accomplish the task.

I've been using Omega PX-309 sensors for this purpose for years. They are expensive, but accurate, very stable and extremely reliable.

outsider

Does the tank have a pipe connection at the bottom? What is the maximum depth of water in the tank?

ma13

Hello,

Of course the sensor must be in contact with the water column. A differential sensor connected to the tank outlet, before the shutoff valve, will accomplish the task.
Ok, I understand what you mean but the fact that I forget to say is that I can not change the existing system. The only thing I can do is put something in the tank. That's why I talked about an absolute sensor, because a differential like the one you're talking about needs me to make a hole in the tank before the exit to put it between the water column and the atmosphere.


A submerged/gauge sensor also needs a barometric sensor to compensate for atmospheric pressure changes.
A differential sensor (two ports) doesn't need that.
Leo..
And of course i need two of them, one for the measure, one for the reference.

Does the tank have a pipe connection at the bottom? What is the maximum depth of water in the tank?
Yes, but as I said, I can not make any changes to it.. Max 2m

jremington

#7
Feb 10, 2018, 12:32 am Last Edit: Feb 10, 2018, 12:38 am by jremington
Your plan will work, but the inside and outside sensors must be matched for accuracy, and they will be expensive.

I use MS5540c pressure sensors to measure water depth in a tide gauge and a couple of rain water tanks.
At <$20 each and ~$3 for a BMP180 for barometric compensation they give better than 5mm accuracy but you do have to have the arduino  provide a 32khz clock signal for the MS5540C.  Another alternative is the MS5540-CM, they are a bit more expensive but are probably easier to use as I don't think require the 32khz clock and can talk I2C or SPI, of course they all require potting in epoxy or silicone.

wvmarle

Sensor we're discussing in this current thread seems to fit the bill.

VERY interesting claims; definitely planning to get one for my hydroponic reservoirs (typical water levels 10-40 cm).
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

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