Guideness in a project that is water related

[MrWater]

Hey everyone
I am building a underwater current measurement device.
This is my first ever practical experience so i am mainly searching the internet for info.
My goal is to measure the current under the surface of the water and on its surface.
We are using high voltage electrical arch above the water (1000[kV]).
The positive lead is above water and the negative lead is underwater.

So far i found a YouTube video demonstrating some methods using a shunt, which looks promising.

https://www.youtube.com/watch?v=_3GPaFuqrxs

I also thought using a clamp, but it is used for ground measurement so i am not sure how it will work.
(something like this:

https://www.aemc.com/products/ground-testers/ground-tester-6416

)

I will be really glad for some guideness, ideas and sources

thank you!

 

[IRstuff]

What is the purpose of measuring the current? Water resistivity isn't measured that way.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[crshears]

And here I was thinking, "Underwater current? What's wrong with a flow-actuated propeller?" Mind, I haven't watched the YT video either...

The positive lead is above water and the negative lead is underwater.

So you'll end up measuring some sort of combined water/air[/contaminant?] resistivity...

Perhaps you should start at the beginning and explain what you are trying to accomplish.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[MrWater]

Hey guys thank you for the answers!
We simulate the effect of lightning on sea water.
we have a jar of sea water and we are using high voltage electrical arch above the water.
we need to measure the electrical current on the surface of the water and under it.
also we would like to measure the electrical field in different depths of the jar.
i hope its clear enough.

i added a picture of the power supply which should convert 3[V] into 1000[kV] (kinda doubt it but ok...).
If you have any methods you could recommend for it, i would be more than glad!
thank you!

 

[MacGyverS2000]

Ain't no way that thing is converting 3V into 1MV.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[argotier]

Are you sure the value you need is 1000 kV??

A 1000 kV impulse voltage generator (at least the type used for power transformer testing) is a huge and complicated equipment! 5-6 meters tall! And expensive, don't forget expensive!

Check here for a 1000 kV model.

But, suppose the little thing you posted works in rising the voltage:

1 - You need to estimate not only the voltage, but also the energy you need (typically in kJ) for your experiments to work properly.
2 - The current is usually measured by a shunt, as you said, somewhere along the current path (usually the return path). You don't need to measured it underwater or in its surface.
3 - You will need some type of digital recorder, like an oscilloscope, to register not only the current peak value, but also it's waveform.

Hope it helps.

 

[FacEngrPE]

If you need to make lightning, use a Marx generator.

https://www.instructables.com/id/Build-a-simple-Marx-Generator/

CAUTION - Marx Generators create dangerous voltages and currents.

Current associated with sparks is an impulse with a very steep leading edge. If you Fourier transform the impulse you will find a significant component of MHz. This makes normal power measuring devices somewhat useless.
Clamp pickups normally do not have the frequency range needed for measuring sparks.
A restive shunt might work but it needs to be followed with a sensor that has a very wide frequency range.

 

[waross]

The ground tester that you linked to is unsuitable.
It is not an Ammeter.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MrWater]

hey guys thanks again for the answers!
The power source is not on my end, my duty is to find a way to measure the EF and current.
The device that generate the "lightning" is already functional (its a small electrical arch).
I think they are wrong and its converting it to 10[KV] max and not 1000[KV] like they think.

what i need help with is to measure the electrical field and the current on different levels of the jar.
especially on the surface of the water.
if you could help me find a device or a guide for building one by myself i would be very grateful

 

[LittleInch]

Some guys have already done this apparently...

https://phys.org/news/2017-06-lightning-powerful-ocean.html

I can see no way for you to get any reliable measurements of the arc / spark or whatever your power supply people come up with when it hits the water and trying could actually kill you and anyone you're holding onto at the time.

"A jar of seawater" doesn't sound like anywhere near big enough.

Is this a project / student experiment?

Nobody can surely be paying you to do this?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[waross]

Put a shunt, grounded at one end for safety, in the return line from your jar to the power supply and derive the current from the voltage developed across the shunt.
A high bandwidth memory scope will be helpful.
You are using a return conductor to the power supply I hope.
This will give you both the peak current and the waveform profile.
If you want to measure the current dispersal in the water someone else will have to help.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[argotier]

I concur with the guys above, this is a dangerous experiment, you better know what you are doing and take due care!

With the current measurement I insist you don't need to do it underwater, just use a shunt in the return path of the electrical circuit.

For EF measurement the thing gets more complicated, I'm not sure what would fit your needs but it should be something like these:

Fiber Optic Electric Field Sensor

Isotropic Optical E-field Sensor

They are remote non-intrusive sensors and you could place a few on different depths. You need to have an idea of the frequency of your discharge and the expected E-field max value to find the proper sensor model.

Be safe.