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Old 2nd April 2016, 09:54 AM   #1
kffern is offline kffern  Australia
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Default HV power supply help

I am trying to build a HV PS for my electrostats and am having a few problems.
I have bought a fluoro invertor and I am having a problem building a voltage multiplier. With 12v AC in I measure 18V at the first cap, 34v at the second cap and 26v on the next and the same till the end.
I built the same using 2 screw terminal blocks and new components just to see if one of the components was bad but it measures the same.
What am I doing wrong? This is supposed to be childs play!

Click the image to open in full size.

With 12v in to the inverter the output starts at around 200v AC and slowly climbs up to around 250V. Only my Fluke autoranging multimeter will read it and it has a lowZ meassage on the display.

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Old 2nd April 2016, 09:57 AM   #2
kffern is offline kffern  Australia
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This will be fed by a variable DC using a LM317 with a trimmer giving 0 to 15v DC.
kffern
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Old 2nd April 2016, 04:56 PM   #3
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You won't be able to reliably measure the voltage with your average multimeter.
The input imepedance of a meter is to low and will load down the multiplier as it won't produce enough current to drive the meter.

I have a whole discussion on this in one of the threads.
I use a very high resistance 1000:1 Voltage divider with a unity gain opamp buffer on the bottom resistor to drive the meter.

This is the most accurate way to measure such voltages.
See this thread for more info and especially post 50 for the complete schematic and details,

how can test the stator insulation and mylar coating?

and this thread,

Newbe Question: ESL bias power supply

My second version uses a 300Megohm resistor stack and I use it to directly measure the output of the step-up transformers directly into my sound card and/or O-Scope!!

jer

P.S. One more thread that may help you,

How to measure bias voltage on Acoustat

Last edited by geraldfryjr; 2nd April 2016 at 05:09 PM.
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Old 2nd April 2016, 05:25 PM   #4
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Here is the post that shows the schematic of my simpler Transformer Test Jig and the power supply for reference.

They both use the same methods just one has a higher resistance voltage divider (Much Better!!) than the other.

Help me fix these poor ML Sequels

jer

P.S. My First version in the HV power supply used the 300meg stack and the Test jig used a 20meg stack Vice-Versa of what I had stated earlier.

Last edited by geraldfryjr; 2nd April 2016 at 05:29 PM.
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Old 2nd April 2016, 05:53 PM   #5
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Quote:
Originally Posted by kffern View Post
...Only my Fluke autoranging multimeter will read it and it has a lowZ meassage on the display.
Which Fluke model do you have?
When operated in lowZ mode the meter input impedance is about 3Kohm.
There should be another AC voltage measurement setting that gives you a 10Mohm input impedance that will not load down the circuit you are measuring so much.
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Old 3rd April 2016, 01:53 AM   #6
kffern is offline kffern  Australia
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Thanks for all those links Jer. I searched HV power supply not bias.

I am using one of these http://www.altronics.com.au/p/k2559-...or-kit/http:// but read nothing with the 12V AC supply - to low I guess. It is as you say but with a 50K pot to calibrate. I set it to 25K which is meant to be close enough if you don't have a reliable reference.
I measured a few of the Kingsound supplies which had voltages scribbled on the bag and they were within 0.1Kv. I can't vary these supplies as I mentioned in my Kingsound thread.
Kingsound King electrostatic

I will hook it to the inverter and see what happens. I haven't found a thread where someone has used the variable DC - inverter - C-W multiplier option.

I had the multiplier mounted on a small prototyping PC board but took it apart thinking I had it wrong.

Regards,
kffern

Last edited by kffern; 3rd April 2016 at 02:00 AM.
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Old 3rd April 2016, 01:57 AM   #7
kffern is offline kffern  Australia
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Quote:
Originally Posted by bolserst View Post
Which Fluke model do you have?
When operated in lowZ mode the meter input impedance is about 3Kohm.
There should be another AC voltage measurement setting that gives you a 10Mohm input impedance that will not load down the circuit you are measuring so much.
Hi bolsert,
Its a Fluke 7-600
Fluke 7-600

I've had this for ages but rarely use it because I thought it was giving trouble but I may have been wrong. Just downloaded the manual.
Thanks,
kffern
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Old 4th April 2016, 02:39 AM   #8
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Quote:
Originally Posted by geraldfryjr View Post
I use a very high resistance 1000:1 Voltage divider
Nobody could be more supportive of creative people doing audio projects. More power to you.

On the other hand, the goof you are making should be a wake-up call that you may be short on the electrical background needed to proceed safely.

Everybody working with ESLs needs a high resistance high voltage meter. Like Gerald, I use 1000:1, 100 meg to 100k. Any digital voltmeter can read voltages across 100kOhm resistor (their input resistances are a bunch of megs).

You can buy high value, low wattage, high voltage resistors (which are special creatures) to form a 100meg chain (plus one 100k ordinary resistor) on eBay from the Ukraine. (I hope you will buy some so I can find out if they are legitimate.)

Ben
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Old 4th April 2016, 08:01 AM   #9
kffern is offline kffern  Australia
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Quote:
Originally Posted by bentoronto View Post
Nobody could be more supportive of creative people doing audio projects. More power to you.

On the other hand, the goof you are making should be a wake-up call that you may be short on the electrical background needed to proceed safely.

Everybody working with ESLs needs a high resistance high voltage meter. Like Gerald, I use 1000:1, 100 meg to 100k. Any digital voltmeter can read voltages across 100kOhm resistor (their input resistances are a bunch of megs).

You can buy high value, low wattage, high voltage resistors (which are special creatures) to form a 100meg chain (plus one 100k ordinary resistor) on eBay from the Ukraine. (I hope you will buy some so I can find out if they are legitimate.)

Ben
I don't know how many times to say this but I am using one of these:

http://www.altronics.com.au/p/k2559-...m-adaptor-kit/
(Silicon Chip Magazine April Ď10) Measuring high voltages on a standard DMM is usually limited to 750AC-1000VDC. This probe allows measurements up to 23-25kV DC as found in CRT based scopes, computer monitors and TVs. High voltages are also commonly found in laser printers, photocopiers and microwave overs.


Thanks Ben, but yet again you type before you read.

kffern
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Old 4th April 2016, 10:20 AM   #10
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Sure. Me real bad boy.
Ben
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