How does water sensor work (in ultrasonic transducers)

[arvinfx]

Hi, I am confused about this sensors how they sense the water is exist or not without contact water!?!?!?!

 

[Sceadwian]

This is the second time (in reference to the first image) I have seen this question asked on the forum, and I wish I could answer it. The only way it can be answered is by dissection of the actual sensors, or by someone that works for a company that uses them and has an 'in' on how they function.

I find myself very curious about the answer myself I wish I could help more.


arvinfx, can you tell us the device names of each of the three devices you have in the images above it may help us find more information.

 

[ccurtis]

This is one way, according to one supplier, but the transducer looks a lot simpler and smaller than the one(s) in your photos.

https://intl.gemssensors.com/uploadedFiles/Literature/exosense_specsheetPRINT.pdf

 

[panic mode]

are you sure it detects water and not any obstacle? one common sensor is ultrasound transducer and can be used to measure fluid level in a tank for example using echo location. it sends pulse, than waits and measures delay until reflection comes back. modern ultrasound transducers are compact, able to distinguish even soft surfaces (like sponge/foam in a car seat) and also can be highly directional (for sound wave) with cone of about 30deg only.

 

[arvinfx]

arvinfx, can you tell us the device names of each of the three devices you have in the images above it may help us find more information.

In catalogs this named "water level sensor"

 

[arvinfx]

are you sure it detects water and not any obstacle?

Yes.

one common sensor is ultrasound transducer and can be used to measure fluid level in a tank for example using echo location. it sends pulse, than waits and measures delay until reflection comes back. modern ultrasound transducers are compact, able to distinguish even soft surfaces (like sponge/foam in a car seat) and also can be highly directional (for sound wave) with cone of about 30deg only.

I knew this but this device is realy small! It looks like a 2W resistor in a varnish tube.

 

[alec_t]

this device is realy small! It looks like a 2W resistor in a varnish tube.

Can't see that in the photos?

 

[panic mode]

are you sure it detects water and not any obstacle?

Yes.

i meant are you sure it detects H2O and not oil, alcohol, powder or any other substances that may be used to fill the container?
this does not do chemical analiasys so answer should be no.

i don't see this as a mystery so maybe i do not get the question.

ultrasound sensors are compact, and they are smaller as the frequency goes up. you produce pulse and wait for reflection. reflection occurs any time
produced pulse encounters change in media density (regardless if the density after some boundary is higher or lower).
this is the same principle as used in time domain reflectometers.

 

[Externet]

Hi. Expanding details...
The sensor detects the presence of water; does not work with other fluid :
http://www.youtube.com/watch?v=J3vD66PE_-o

There is no exposed electrodes, it is encapsulated in shrink tubing,

It seems to have only one axial lead each end,

The unit it is attached to is a fogger :
http://www.ebay.com/sch/i.html?_nkw=ultrasonic+mister
To shut it off if not submerged

And the unit is cheap enough to believe it is a simple clever sensor than an elaborated one;

And the fogger device is not ultrasonic, it is RF at about 2MHz driving a piezoelectric disc;

And schematics I found on the net do not show the sensor, just the driving RF circuitry.

And yes, I have one that prefer not to dissect, and tried, does not work in other fluid.

Edited: added ----> http://www.mainlandmart.com/foggers.html

 

[alec_t]

It looks like a 2W resistor in a varnish tube.

Does the tube contain (apart from the 'resistor') a liquid or air?
If I were making a cheap sensor I'd use a thermistor inside an oil-filled tube, so that there is good electrical insulation and good thermal conductivity between the thermistor and its surroundings. Pass a constant current through the thermistor. If the surroundings are air/water the thermistor will/won't heat up and significantly change the resistance of the thermistor.

 

[misterT]

It is a tiny plastic float attached to a mechanical switch.
https://wolfstone.halloweenhost.com/Fog/fogus_UltrasonicFog.html

 

[Externet]

Mr.T: Is that a guess or you can support your claim ?

 

[misterT]

Well it could measure conductivity also, but those look like floaters to me.. Take a look at the link.
https://wolfstone.halloweenhost.com/Fog/fogus_UltrasonicFog.html#WaterLevelSensor

EDIT: Conductivity sensor seems to be the most common type, so those are probably conductivity sensors. I got confused because they look like floaters. Check the manual if it says anything about using the device in distilled water.

EDIT2: Ok, this manual says "Do not use Distilled or Pure water, whilst the fogger water sensor will not work properly." So it is most likely a conductivity sensor. And the sensor looks like the one in the first picture (in the first post).

 

[Sceadwian]

Mister T there are three images there. Only one looks like it could be a float. What's confusing about the resistor shaped one is if it's a conductivity sensor how does it work because it's sealed..

 

[misterT]

Maybe it measures the capacitance between the probe and the fogger casing.. like this one: https://www.hawker-electronics.co.uk/ls_magicap

 

[Sceadwian]

They're cheap enough it's tempting to buy one just to take the darn thing apart and figure it out =)
I know the only note I found in a PDF about one of them is that the sensor can be affected by hard water buildup.

 

[Externet]

The schematic, which I do not understand the hard to read description well enough, plus the patent 7467786 data, implies a capacitive sensor. Then it should be just a capacitor; with a particular effect/value obtained only with water.
https://www.8085projects.info/image.asp?picture=Atomizer circuit..jpg

Edited: added----> The description is in: https://www.8085projects.info/post/Atomizer-circuit.aspx

 

[arvinfx]

I see many of guys like to khow about it! Amazing! But I thinks it is a secret now! because nobudy was able to find an answer ,Neither do I

Guys, I have one of them but It`s not mine so I can`t disassemble it. But as I told you , IT HAS NOT ANY CONTACT WITH WATER, AND ALSO IT`S STRONGLY IMMOBILE AND FIXED. so it is not a floater.

 

[arvinfx]

Can't see that in the photos?

On first picture you can see but the angle in the picture is not good, meybe at blow link you will be able to see more clearer.

http://www.mainlandmart.com/foggers.html

 

[arvinfx]

Hey gays I have some picture about inside of this water sensor see:

What is your GUESS ?