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-   -   Voltmeter to monitor an Electrostatic speaker 10000 Volt power supply (http://www.diyaudio.com/forums/planars-exotics/29288-voltmeter-monitor-electrostatic-speaker-10000-volt-power-supply.html)

kermeeng 1st March 2004 01:10 PM

Voltmeter to monitor an Electrostatic speaker 10000 Volt power supply
 
Dear All,

Please can you help me find or specify a voltmeter suitable for monitoring a 10000V power supply for an Electrostatic speaker?

The voltmeter must have an extremely high resistance probably much greater than 10,000,000,000 ohms to avoid over loading the power supply. The power supply has very HIGH internal resiatance.

Electrostatic voltmeters I have seen are either low accuracy (field meters?) or expensive that is greater 1500?

Yours sincerely

George Kermeen
Electronic Engineer
Dudley Designs and Technical Services Ltd
email dudleydesigns@aol.com

till 1st March 2004 02:29 PM

does it need to be fast? else, why not a voltage divider 10000:1 with desired resistance, and a ADC over the resitor with about 1V across it? As the ADCs input would be a capacitor that is charged, the slower the ADC is, the larger the resistors could be.

SY 1st March 2004 02:33 PM

What you want to do is build a high voltage probe. That's most easily done by stringing a bunch of high value resistors in series, and setting up the voltage divider that till suggested. Using a bunch of resistors in series helps get past max voltage ratings. Make sure your substrate has VERY good insulation properties- plain epoxy may not do.

dhaen 1st March 2004 02:39 PM

Not what you asked, but.....
 
If you know the capacitance of the ES panel, you could add a series cap of suitable value, and measure with a low voltage electrostatic meter across that.
Alternatively, by knowing the source impedance of the power supply, you could use the method mentioned here:
http://www.quadesl.org/FAQs/body_faqs.html

jackinnj 1st March 2004 02:58 PM

safety first:

i don't think that a HV probe is something that easily built from scratch -- firstly with common plastics the conductivity can be much higher than those seen published due to the fillers etc. used to enhance strength. you want a plastic which is not hydrophilic in any case, you want to make sure that the there is no way your hand or fingers can slip and come into close proximity to the HV circuit.

secondly, common resistors are non-linear above a few hundred volts -- there are special high voltage resistors for this purpose

my 2 cents -- you can buy a good B&K, Heath, Fluke or Eico HV probe on the bay -- anywhere from $20 to $60. it doesn't take more than a few hundred uA to stop your heart.

SY 1st March 2004 03:00 PM

All good points, Jack. Thanks.

The plastic I had in mind was Teflon or UHMW.

dhaen 1st March 2004 03:09 PM

Reminder:
He's asking for 10G ohm.
The available probes I've seen are 100M to 1G.

ashok 1st March 2004 03:09 PM

Shocking the heart
 
Quote:

doesn't take more than a few hundred uA to stop your heart
Yeah, and it gives you about 3 more minutes ( depending on temp ) till your brain shuts down and it gives you time to scream (silently) and curse yourself for not having been more careful. It must be awful -- shutting down almost consciously --.......... it happened to someone I knew very well ! Awful for everyone else too.
So BE CAREFUL ! People care more about you than you imagine !

Be safe and have fun.
Cheers.

Tobbe_L 1st March 2004 03:13 PM

You can easily find high-voltage probes that can measure up to 40 kV, so that is not a problem.
But finding something with an input impedance of more than 10 GOhm will be a problem, to be honest I am not even sure such a thing exist. You also need a decent multimeter (with an input impedance >10 MOhm) in order to use such a probe.

Are you sure 1 GOhm would not be enough? Then for example a Fluke 80k-15 would probably work.

I should also point out that I think it would be VERY difficult to make a DIY probe with a imput impedance anywhere near what you can find in commercial probes.

jackinnj 1st March 2004 04:07 PM

Quote:

Originally posted by Tobbe_L
You can easily find high-voltage probes that can measure up to 40 kV, so that is not a problem.
But finding something with an input impedance of more than 10 GOhm will be a problem, to be honest I am not even sure such a thing exist. You also need a decent multimeter (with an input impedance >10 MOhm) in order to use such a probe.

Are you sure 1 GOhm would not be enough? Then for example a Fluke 80k-15 would probably work.

I should also point out that I think it would be VERY difficult to make a DIY probe with a imput impedance anywhere near what you can find in commercial probes.

maybe with the TEK R7704 I am desparately trying to give away I should include a HV probe. :)


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