Pyrus
Lv 6

# Electricity in water and its effects.?

I'm designing my own water level indicator, and it requires 9V to work, including the wire that is going down the water tank. My circuit will work, and made sure that the circuit is only activated when pressing a push button. This also includes the wire that is going through the water. Now the thing is that it does not include any transistors. So, my dad for some reason is stressing about the current that will go through the water when the user will press the button to check the water level. This is why I wanted to ask what is considered as a safe current inside the water. Also, what are the risks of the chemical reaction that the water might undergo with the electricity. The LEDs, by the way, have 2.2 Kohm resistors.

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• 1 year ago
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Tap water is not conductive enough to measure water level this way. The conductivity of the water will vary wildly over a day or week too much to be dependable unless you are on a private well. A 9V battery will not provide enough current to be useful. Up to 35V Dc is considered safe for this type of application If it is activated with a switch to measure. This is the supply on a phone system ~35V. You don't need to worry about electrolysis if it is momentary. Have fun and learn from it.

AC may work better if it is transformer isolated from the line. 30VAC RMS.

• 1 year ago

Electrolysis of water happens at 1.23V. Anything below this, and electrolysis won't occur. Also as mentioned, pure water is a poor conductor, which is why electricity tends to flow through people (salt water) in water instead of around them.

So . . . just nix the current altogether. The relative dielectric of water is huge, like 80. So imagine you have two capacitors in series, one is a standard, the other is made up of two conductors. Apply 1V across them and measure the voltage on your standard. As water flows between the two sense conductors, the capacitance will change. This will change your measured voltage. There will be no current, no matter what happens, because of the first capacitor.

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• 1 year ago

You have an amazing invention if you can stick a wire down a tank and measure the water level with a battery and a meter. The level sensors I have worked with operate on generally one of three technologies: 1. for a specific level a float with a magnet in it and a reed switch. Water rises up to raise float, magnet surrounds reed switch and makes switch. 2. for a variable output level, i.e. how many inches from the cover, ultrasonic sensor is one way. Transmitter sens us signal down, bounces off top of liquid, returns, time is measured, distance is calculated. Easy to check calibration with a tape measure. 3. Long stick that float can go up and down over, with reed switches every half inch or so.

So if you want the analog sensor with just a wire, battery, and meter, good luck.

Source(s): Been a mechanical engineer for a long time, measured levels in many different liquids using all of the above techniques. Big fan of Gems level sensors.
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• M.
Lv 7
1 year ago

What kind of "water tank"?

Clean water will not conduct 9 volts.

Dirty water may conduct 9 volts.

Salty water will conduct 9 volts.

In the case of your apparent LED circuit, it is current that needs to flow to light the LED. It may require 20 milliamps or more to light.

If you expect water to operate as a "switch", then your idea is not likely to work.

Better experiment with a glass of water before you waste time wiring the tank.

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• 1 year ago

Unless you push a couple of probes through your skin and then connect them to the 9V battery (as some idiot did some years ago (https://darwinawards.com/darwin/darwin1999-50.html... the current from a 9V battery is pretty safe, water or no water.

However, your problem, as others already pointed out, will be electrolysis. That will (pretty quickly) corrode your electrodes and (at least theoretically possible) create an explosive air/hydrogen mixture.

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• 1 year ago

How is your level meter supposed to work? Water is anything but a good conductor of electricity. A cup of water will have anywhere from 200k ohms to 500k ohms of resistance! That will only allow about 20 micro amps to flow with a 9 volt battery. The acids on your tongue in your mouth can generate half that much!

You will need to use transistors to amplify that small amount of current. Also, the resistance of the water will not change as the water level rises. So you would have to have a separate wire and amplification for each LED, with each wire spaced a little higher than the one below it.

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• 1 year ago

With a battery powered circuit, the problem is not safety, it is electrolysis (as billrussel42 says).

Any time you have any current passing through electrodes in water normal, the water is being separated to hydrogen and oxygen at the electrodes. That corrodes the electrodes and will taint the water to some extent.

Other substances such as minerals dissolved in the water may also be electrolysed and broken down.

All properly designed gear that senses via electrodes in water uses a small AC signal, that cancels out any electrolysis effects.

As Bill says, if you are doing it with DC, keep the current to an absolute minimum - and use stainless steel electrodes.

The conductivity of water depends on what is dissolved in it, eg. you will likely get a lower resistance if you are in a "hard water" region than with soft water.

(As a point of fact, deionised water is an insulator, it does not conduct at all).

Wire electrodes that are not particularly deep, so actually sensing level, may have eg. 100K resistance between them, far too high to directly run a LED.

You will likely need either a darlington transistor or a FET, to get consistent results with a high impedance sensor.

[Electronics designer and programmer for 40+ years; among many other things I have designed water sense circuits for commercial products].

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• arther
Lv 5
1 year ago

I doubt the battery contains enough energy to hurt anyone you wont get an electric shock from your level indicator Id use 2 AA batterys if possible

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• 1 year ago

yes, you will get electrolysis action, which will corrode the copper electrodes, unless you used precious metal electrodes. Best to keep the current in the 1 µA region or less. Which means a darlington amplifier, or an opamp.

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• 1 year ago

Your creation sounds quite cheap no offense. I'm a bit worried the low-quality equipment might fail once drenched in water.

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