EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: ricko_uk on January 24, 2022, 11:09:28 pm
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Hi,
I am looking for a low-cost liquid level sensor for sensing the level of extremely mild caustic soda. It is so mild and diluted that you can even wash you can keep your hands in it for long time without any issues.
It is for a production product, so I did quite a bit of research but they are either not for a sealed container or very expensive.
I have also come across some thermistor level sensor which I am not sure how reliable or accurate they are... I can understand on-off (using a second one as reference) but level..?
I simple to make I can also consider designing the float and use stock components for the rest (but the sealing still remains an issue unless it can be detected through the metal enclosure.
In summary
- the liquid to be measured is inside a sealed (air tight) tank.
- the tank containing the liquid is stainless steel
- the displacement is 130mm to 150mm
- precision does not nee to be high at all, even 5mm "granularity/accuracy" (+/-2.5mm) in reading is acceptable
Does anybody have any suggestion on either some stock parts or ways to make a custom one?
Many thanks :)
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If it was a plastic container, a simple foil stick-on capacitive sensor could work.
You could also use a loadcell, or repurpose a small scale for DIY, and measure the change in weight from empty to full.
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- the tank containing the liquid is stainless steel
If it was a plastic container, a simple foil stick-on capacitive sensor could work.
How about a stick-on capacitive sensor attached to a dipstick inserted vertically into the container?
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Thank you both.
@ledtester,
what kind of capacitive sensor are you thinking of?
Thank you :)
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Have a look at this video:
How to make a Capacitive Water Level Sensor - Heilman Hackatronics
https://youtu.be/nO_GJJ6HfTI
Alternatively you could etch an interlocking comb pattern on a single copper PCB strip to form the capacitor.
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@ledtester
ahaha, thank you, that is the same video I was watching soon after replying. The only thing that might not be reliable enough is the sealing.
I was wondering is some reliable sealed ultrasonic ranging solution can be implemented at low cost?
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Ultrasonic sensing (sensor firing down form top of tank) would avoid/reduce the whole waterproofing problem.
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Thank you @mikeselectricstuff,
the tank is small and can be tilted accidentally so I was looking for some sealed ultrasonic sensor which is also relatively low cost excluding the electronics. Maybe 20-30USD at most in quantities of few 100s.
But couldn't find any around that price range, I assume also because it includes the electronics.
Does anybody know of any without the integrated electronics so they might be a lot cheaper?
Thank you
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You might find this guy's experience with a hobbyist ultrasonic senor helpful:
Ultrasonic distance sensor as an oil level gauge - Matthias random stuff
https://youtu.be/c0SpsUMR2fU
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How quickly does the level of the tank change? You can use a basic sensor, and ignore tilting or other effects perhaps if you simply average lots of readings if the level only changes slowly?
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Thank you both.
@max_torque,
the level changes extremely slowly, maybe a mm every 30 minutes.
What do you mean "You can use a basic sensor"? What basic sensor? That's what I am asking.
Thank you
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Thank you both.
@max_torque,
the level changes extremely slowly, maybe a mm every 30 minutes.
What do you mean "You can use a basic sensor"? What basic sensor? That's what I am asking.
Thank you
To find the one used in the video just search Amazon/Ebay/Aliexpress for "arduino ultrasonic sensor".
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How about tapping a pressure sensor into the bottom of the tank. I did this for a caustic tank at a textile mill once. Also did it for a fuel oil tank at the same plant.
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Thank you @mikeselectricstuff,
the tank is small and can be tilted accidentally so I was looking for some sealed ultrasonic sensor which is also relatively low cost excluding the electronics. Maybe 20-30USD at most in quantities of few 100s.
But couldn't find any around that price range, I assume also because it includes the electronics.
Does anybody know of any without the integrated electronics so they might be a lot cheaper?
You can buy these. They are called ultrasonic transducers. You'll have to build the electronics yourself though. The distance they can measure depends on the shape. A relatively simple microcontroller circuit can be used to process the output of the transducer (reading the echo of a pulse sent out). If the sensors are close to eachoter (say up to 20 meters) you can build a central unit that deals with a whole bunch of sensors.
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Ultrasonic has a lot of problems in tanks, in industry ultrasonic is often avoided.
Fine if you have consistent temperature, humidity and pressure in the vessel. These effects of course inter-play with each other, especially in a closed vessel. Most industrial US sensors for liquid level are temp compensated and use algoritmic magic to avoid effects of air currents etc. In my experience you are better with anything but ultrasonic. Main industrial methods are Microwave(radar type) Microwave(proximity type) Capacitive, differential pressure, load cells...