working principle of water level sensor

how actually this sensor works? Can someone tell me? thank you

The metal strips have resistance. When in touch with water a current will flow. Depending on how deep it is in the water the resistance will vary.

Is that actually a water level sensor?

means the resistance of the metal strips will be changing if it exposed to water?

it is not actually water level sensor, you may call it rain sensor.
when water falls over adjoining metal strips it completes the circuit and you get signal from pin.

oh i see so whenever the metal strips get exposed to water it will result a change of resistance due to different water level, is this concept correct?

weesin:
oh i see so whenever the metal strips get exposed to water it will result a change of resistance due to different water level, is this concept correct?

I think that's the gist of it, the sensor provides an analog output proportional to the resistance between the metal strips (electrodes). In your photo, there appears to be a transistor and a couple resistors (plus a LED and resistor to indicate power) that amplifies the current between the electrodes. I've attached a link to a soil moisture sensor with schematic that operates on this principle. To use the sensor, you would apply power and ground to the designated pins and connect the "S" pin to an Arduino analog input pin and read that with the analogread() function.

http://www.elecfreaks.com/wiki/index.php?title=Octopus_Soil_Moisture_Sensor_Brick

Mr Mark, thank you for your explanation
But I still got some doubt about it.
so if I find the resistance of the metal strip, can I use this formula?
R=pl/A
I need to have a formula to use in Labview but I don't really know what formula should I use.
Hope you can help me.

weesin:
so if I find the resistance of the metal strip, can I use this formula?
R=pL/A

The resistance of the metal is essentially zero. You can use that formula in principle, but what you want is the resistance of the water, not the metal strip. In the formula then, L is the gap between the electrodes, p is the resistivity of water (which is a strong function of impurities), and A is proportional to the amount of the sensor covered by water.

My suggestion would be to build up the sensor prototype and empirically calibrate it for your application. That is, take data points for the sensor area barely covered by water, half cover, and fully covered. My expectation is that the measured voltage is going to be close to a linear function of water level, but I don't have much experience or special expertise with this particular sensor.

Mr Mark, i did the calibration with few water level, even though the voltage is increasing but then the graph is not that linear.

It might be helpful if you posted a picture of the graph and any information you might have on the particular sensor you're using. It may be that it's designed to simply detect presence or absence of water, not a proportional output.

That is not a water level sensor. It just detects if water is there.

The resistance will be a function of water level, impurities in the water, and time. It will vary wildly between open circuit for distilled water, to a few kilo ohms or less for salty water. And it will rise or fall over time as the metal corrodes away, making less metal, but more ions in the water.

DC in water is very prone to cause corrosion very quickly, depending on the materials you used. I discussed a few alternatives in an older post here, if you are actually looking for a level sensor.

Hi.
Check this youtube.

Tom... :slight_smile: