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Author Topic: BMP180 in water  (Read 2014 times)
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Tom1234
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« on: March 13, 2021, 11:17:51 23:17 »

I would like to use BMP180 sensor to measure pressure to a tank with water.

I would like to ask how to isolate the pcb from the water?
how to use it in the tank which is full with water?
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pickit2
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« Reply #1 on: March 13, 2021, 11:44:43 23:44 »

one way to try to do it with a BMP180 is in a sealed tube, with a diaphragm to transfer the water pressure to barometric pressure.
a bit like putting the sensor in a plastic bag like a balloon and pressing the balloon to increase the reading. 

BMP180 is not a water pressure sensor, it is to measure atmospheric pressure. there are better devices ready to use.
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cdr_spock
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« Reply #2 on: March 14, 2021, 07:45:56 07:45 »

Hi,
BMP180 is not a good choice for water pressure measurement. Instead try  sensor like MPX5010DP( this is for 10kpa) or sensor of this family.
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Sideshow Bob
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« Reply #3 on: March 14, 2021, 08:14:46 08:14 »

I agree with others. Get a proper sensor for fluids. Your idea is wrong on so many points
By the way for freshwater and pressure you can use this site
https://www.engineeringtoolbox.com/hydrostatic-pressure-water-d_1632.html
So for up to 1 meter height of fluid column a 10Kpa sensor might do the job. But for a higher height of fluid column you can not use a 10Kpa sensor
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cesare
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« Reply #4 on: March 14, 2021, 08:22:52 08:22 »

In an underwater application I used the MS583730BA01-50 from TE connectivity
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sadman
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« Reply #5 on: March 15, 2021, 06:11:04 18:11 »

A water Level and measurement system based on Motorola pressure sensor was published in three part in silicon chip I will extract the article and share here tomorrow

https://www.siliconchip.com.au/Issue/2007/November/PIC-Based+Water-Tank+Level+Meter%3B+Pt.1

https://www.siliconchip.com.au/Issue/2007/December/PIC-Based+Water-Tank+Level+Meter%3B+Pt.2

https://www.siliconchip.com.au/Issue/2008/January/Water+Tank+Level+Meter%2C+Pt.3%3A+The+Base+Station

https://www.siliconchip.com.au/Issue/2008/January/Improving+The+Water+Tank+Level+Meter+Pressure+Sensor

https://www.siliconchip.com.au/Issue/2018/February/A+Water+Tank+Level+Meter+with+WiFi+and+More%21

sadman






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sadman
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« Reply #6 on: March 16, 2021, 06:03:17 06:03 »

As promise here is the all articles with PCB files and source code
« Last Edit: March 16, 2021, 07:26:29 07:26 by sadman » Logged
Poty
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« Reply #7 on: March 16, 2021, 03:26:23 15:26 »

Hi Tom. I`m in this search too, and what they reccomend is right, but depending on what you want to do.
You must define the water height that you want to control. A normal house water tank, a toilet tank, an industrial tank, etc.
Basically, the height of the fluid from the bottom of the tank to the surface of fluid. Most applications in a normal house uses around 2 meters max... but toilets use 0.5 meters maximum.
And, of course, depends on the precision of reading that you want. YouŽll get more precision with a sensor with a range as close as you can get to the range of the tank.
Always keep in mind to cosider temperature effects, height of the complete sistem, density of fluid, and with the good advice from pickit2, the resistance opposed by a membrane.
You have to test diffferent alternatives, like latex from ballons, condoms, or maybe something thicker, depending on the pressure (height) of the fluid.
Direct measurement may work, but depends on the kind of fluid and the useful life span that you want.
In that case, remember that if you use a pipe or a hose (for example) from the base of the tank, to the position of the sensor, the air contained in it will have vapor of the fluid, which can be agressive to the sensor or the pcb of the circuit.
You can use epoxy to pot the system, leaving exposed only the sensor, but keep in mind the kind of liquid. In example, tap water usually contains chlorine, which is VERY agressive
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comlekciler
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« Reply #8 on: March 16, 2021, 03:44:07 15:44 »

...
By the way for freshwater and pressure you can use this site
https://www.engineeringtoolbox.com/hydrostatic-pressure-water-d_1632.html
...
If you do not want to deal with formulas, you can create a table using the formulas on this website and use it quickly in the processor. Of course, it is necessary to determine a correct sensor first.
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Sideshow Bob
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« Reply #9 on: March 16, 2021, 04:11:33 16:11 »

Try these searches on google. Should work if the tank is uniform. But you may perhaps get problems with condense etc
https://www.google.com/search?q=Ultrasonic+Sensors+for+Water+Level+Measuremen
https://www.google.com/search?q=water+proximity+sensor
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cesare
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« Reply #10 on: March 16, 2021, 09:14:44 21:14 »

I have been presented a report from ST that uses VL53L0X to detect the liquid level in a tank. Obiuosly the sensor is on the top face of the tank looking to the liquid surface.
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Poty
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« Reply #11 on: March 17, 2021, 04:41:06 04:41 »

Well, VL53L0X has a range of 2meter maximum (6Ž6.7"), so, if your tank is lower, it can work. But you need to be sure that the reflectant surface (water or any fluid) is calm, so the reflection is accurate. This can be a problem using this kind of sensor. Ultrasonic have a faster and more accurate response in short time. See Sideshow Bob answer.

Posted on: 17 March 2021, 01:01:47 - Automerged

Just got the reference from ST.... liquid level sensor ("time of flight" technology) will be available on July 2021. Same question... will it work with uneven surfaces? or will have to analyze a statistic response?
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Poty
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« Reply #12 on: March 21, 2021, 10:30:01 22:30 »

Besides all those indications, you must consider which kind of sensor are you selecting... Absolute or relative pressure measurement. Think about this. A barometric sensor, which ranges between 300 to 1100 hpa (means 30 to 110 kPa, or 3.06 to 11.2 m H2O column) is an absolute one. AS an example, lets supose that you want to use it to measure 2m of water.... as a basis, sensor starts with a reading of atmospheric pressure at the place where it is located... say 1bar=10m H2O (ocean level)... so, you can only measure a column of 1.2m H2O, to keep in the range of the sensor. And more, youŽll have to setup the sensor to the original atmospheric pressure, and as it changes, youŽll lose your reference and will get erroneous readings. So, you canŽt use an absolute sensor if you want a precise reading.
There are people in here that lead us to think, thanks to them.


Posted on: 21 March 2021, 19:25:29 - Automerged

Here I found the basis of the idea, using a pressure sensor to monitor liquid levels:
https://www.ti.com/lit/an/snaa127/snaa127.pdf.
Enjoy!
Regards,
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Poty
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« Reply #13 on: March 29, 2021, 10:06:42 22:06 »

New things to test... an arduino ready pressure sensor and an ADC from a load cell. Check https://www.sonsivri.to/forum/index.php?topic=69145.msg200446#msg200446
Regards!
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