how to measure extremely high voltage?

[large_ghostman]

It needs precise control so a piezo is out, I cant tell you the chemical I am using to grow the crystal or the parent police will confiscate it! But there is a certain chemical that you can grow a crystal from (like many), this particular chemical's crystal has some really neat properties if you apply high voltage spikes as it grows. I read about it in a university paper I found in dads stash, apparently you can realign the crystal structure with high voltage short pulses. This apparently gives the crystal some odd properties. The paper has never been published (no idea why) but was done by a PhD student and someone my dad knows.
Took me ages to get hold of the chemical!

 

[dr pepper]

Now you have us all guessing.
I tried messing with ferrofluid when I was at school, it does some weird stuff too.
So how does the electric field affect growth?
Controlling high tension might be tricky, I can see now why you want to measure it.
Another indirect approach would be to use a spark gap, air is no use as the volts/mm will change with temp and draughts, but maybe in a container full of co2 or nitrogen it would be more predicatble.
A squirt from a mig weld set would fill a jam jar full of co2, if thats the gas used.

 

[large_ghostman]

The gas is helium, the electro pulses make the crystal grow with aligned plates. I will try and scan the paper its interesting stuff! it has to be done in a bell jar with a glass plate bottom. And in a fume cupboard

 

[4pyros]

LG; I would like to read the paper. Sounds interesting.

 

[4pyros]

Could you use a resister divider something like this?
**broken link removed**
Heres how using spark length.
http://www.kronjaeger.com/hv/hv/msr/spk/index.html

 

[chemelec]

Could you use a resister divider something like this?
**broken link removed**

That will Never Work on a Car Coil.
Not with those LOW VALUE Resistors.

Due to such LOW Current Available, The Car coil output will get pulled Down to just a Few Volts.

You Need a Divider with High Voltage Types of Resistors and With Values up in the GIG Ohms.
I do this Quite Often and I have Gig-Ohm and also some Tera-Ohm, HV Resistors.

The Resistor in the Picture above is 15 Gig-Ohm, rated at 37 KV and its 6 inches long.

 

[4pyros]

Here is an old thread for your reading pleasure,
https://www.electro-tech-online.com/threads/how-to-measure-high-voltage.31307/

 

[misterT]

Couple of more links to videos:

Skip to 21:30 to see how they measure the output voltage of this high voltage generator:
https://www.youtube.com/watch?feature=player_detailpage&v=sKcH4JxnxbQ#t=1293

 

[ghostman11]

I am not going to get a chance to see LG or talk to him today, I am off for a day or so in an hour. I have left him a note but I am posting this as well, call it a guarantee he reads it.


OK I have been offline for a bit, not read much for a while. THIS IS NOT GOING TO HAPPEN!!!! under NO circumstances are you to go anywhere near the tube with the chemical in!! Dont tell your mum where it is I dont want her anywhere near it. You have no idea how dangerous that stuff is, how did you even get hold of it?

For everyone else thanks for the help, this is some information you didnt know.
The crystal I think he is talking about is a very unstable Highly toxic chemical, the paper hasnt been published yet, but I will post here once its published (June).
GM11

 

[cowboybob]

Ol' LG's a bit of a trial, eh GM11??!!

That happens with a turbo-charged brain...

 

[large_ghostman]

Ermm I got it from a mate at the uni you worked at! its still in the flask and sealed! Its ok dad its in a nitrogen flask thing so its solid not gaseous, cant you show me how to do it?
p.s I have cleaned the car out for you and swept the workshop floor!

 

[dr pepper]

Oops you've been rumbled LG.

Unstable gases, high voltage sparks, no no.

 

[chemelec]

Looking at the Video on Post #28, it appears his Resistors are just 1/4 watt resistors.
1/4 watt resistors are Only rated at 200 Volts.
Even if they are 1/2 watt resistors, they are just rated at 450 Volts.

Neither of these are Suitable for measuring a 15+KV Car Coil.
They will Arc over internally.

 

[large_ghostman]

The gas isnt explosive, its just that there is a chance that it can give off fair amounts of hydrogen cyanide if your not careful! But if you do it correctly then its ok and pretty safe (ish). The crystal I am trying to grow is a kind of cyanate, with some cool properties.
I am probably in a bit of bother though. I have hid it in dads lab so its safe! Oh well I will wait until tomorrow to find out what kind of trouble I am in!

 

[large_ghostman]

Thanks for the video's BTW some good stuff

 

[Ratchit]

How do I measure very very high voltages? there are from a car ignition coil? no expensive answers no 1000x scope probes, but I have a x10 probe lol. I need to measure the output from a ignition coil with 18V going through it on the nice side, what I want to measure is the output. I need around 31,000V lowish Current (around 200mA) its for growing a crystal, well for kind of altering the shape as it grows.

Why isn't this posting in the High Voltage Subthread?

Ratch

 

[dr pepper]

Yuk cyanide, nasty.

They had tanks of the stuff at leyland motors, they used it for chrome plating, untill they got told to get shut of it.