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
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
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.
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
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
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.
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.
Shocking the 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.
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.
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.
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.
Re: Re: Voltmeter to monitor an Electrostatic speaker 10000 Volt power supply
Well not quite - the high voltage power supply of an electrostatic speaker is typically set up with high impedance on purpose for a number of reasons. The most important (functional) is to keep current from flowing as the diaphragm moves (i.e keeping the charge constant much like a restrictor). (Also note that high voltage electronics does not work quite like we are used to)
Now, I recommend that you use an electrostatic voltmeter for such duty as you will most likely draw down the voltage significantly just by loading it.
Petter
awboy said:
Well not quite - the high voltage power supply of an electrostatic speaker is typically set up with high impedance on purpose for a number of reasons. The most important (functional) is to keep current from flowing as the diaphragm moves (i.e keeping the charge constant much like a restrictor). (Also note that high voltage electronics does not work quite like we are used to)
Now, I recommend that you use an electrostatic voltmeter for such duty as you will most likely draw down the voltage significantly just by loading it.
Petter
Conclusion VL can be measured with 100,000,000,000 ohm meter with less than 1% error
Thank you all for the help.
In response to Petter's recommendation.
Has anybody got approximate impedance figures RS for high voltage power supplies?
From the assumption that the probe has 1,000,000,000 ohm input resistance RP say (RS catalogue Stock No 360-0300)
and dhaen's internet reference as follows
Why don't I get 6kV when I measure the EHT's Bass Panel pin?Are you using an electrostatic voltmeter? (Probably not) If you are using a probe attached to an ordinary DVM then expect to read somewhere around 3.9 to 4.2 kV with no bass panels connected and a perfectly good EHT supply.
I estimate an electrostatic HV power supply resistance RS
can be calculated from the power supply open circuit voltage VP = 6KV
The estimated probe resistance RL = 1,000,000,000 ohms
and the loaded power supply voltage VL = 3.9KV
from
VL = VP * RL/(RS+RL)
VL*RS + VL*RL = VP*RL
RS =RL * (VP-VL)/ VL = 1 * (6-3.9)/3.9 = 0.538 G Ohms
Thank you all for the help.
In response to Petter's recommendation.
Has anybody got approximate impedance figures RS for high voltage power supplies?
From the assumption that the probe has 1,000,000,000 ohm input resistance RP say (RS catalogue Stock No 360-0300)
and dhaen's internet reference as follows
Why don't I get 6kV when I measure the EHT's Bass Panel pin?Are you using an electrostatic voltmeter? (Probably not) If you are using a probe attached to an ordinary DVM then expect to read somewhere around 3.9 to 4.2 kV with no bass panels connected and a perfectly good EHT supply.
I estimate an electrostatic HV power supply resistance RS
can be calculated from the power supply open circuit voltage VP = 6KV
The estimated probe resistance RL = 1,000,000,000 ohms
and the loaded power supply voltage VL = 3.9KV
from
VL = VP * RL/(RS+RL)
VL*RS + VL*RL = VP*RL
RS =RL * (VP-VL)/ VL = 1 * (6-3.9)/3.9 = 0.538 G Ohms
It is a capacitor as is pretty much every thing else 
The way it works is that two very thin sheets of metal separate as the voltage gets too high. In effect, what happens is that electrostatic forces force these apart. The good news is that it is infinite resistance. The bad news is that it is not particularly accurate ...
so I did a search on Google and one of the links that came up was http://www.electrotechsystems.com/ProductInfo.asp?ProdID=67 which seems to be a similar sort of thing except that technology has advanced since I went to college
Petter
The way it works is that two very thin sheets of metal separate as the voltage gets too high. In effect, what happens is that electrostatic forces force these apart. The good news is that it is infinite resistance. The bad news is that it is not particularly accurate ...
so I did a search on Google and one of the links that came up was http://www.electrotechsystems.com/ProductInfo.asp?ProdID=67 which seems to be a similar sort of thing except that technology has advanced since I went to college
Petter
an extra warning,
I thought I'd hop in here too.
Anything more than 50 volts is capable of killing a person. Much lower voltages may kill if current is high.
We read of ideas to try to be safe handling higher voltages in this thread.
Here's my advice. A heavy set of rubber gloves over a set of light weight leather gloves, but only used if power is turned off and leads checked for potential power. Then and only then hook up your test probe and back away to power up. At no time ever, get within touching range while the power is on!
Each time you shut down, check for potential energy on each lead before handline( with gloved hands ).
Using "some sort of plastic" sounds like an accident waiting to happen. Sorry, but true. My advice is find something electrically suitable or forget this step.
Guys remember this, learning the meaning of safety late, cannot bring back the past once you get hurt or worse. Work safe with safe tools. Think about your tools being safe for each project.
Here's for continuing this thread. I hope there's some rewarding reading following!!!
GH
I thought I'd hop in here too.
Anything more than 50 volts is capable of killing a person. Much lower voltages may kill if current is high.
We read of ideas to try to be safe handling higher voltages in this thread.
Here's my advice. A heavy set of rubber gloves over a set of light weight leather gloves, but only used if power is turned off and leads checked for potential power. Then and only then hook up your test probe and back away to power up. At no time ever, get within touching range while the power is on!
Each time you shut down, check for potential energy on each lead before handline( with gloved hands ).
Using "some sort of plastic" sounds like an accident waiting to happen. Sorry, but true. My advice is find something electrically suitable or forget this step.
Guys remember this, learning the meaning of safety late, cannot bring back the past once you get hurt or worse. Work safe with safe tools. Think about your tools being safe for each project.
Here's for continuing this thread. I hope there's some rewarding reading following!!!
GH
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