HV Meters For Nixie Testing

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Mac Doktor

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May 17, 2022, 6:53:35 PMMay 17
to neonixie-l
This may be interest to many here. I have the PRO Nixie Tester:

https://nixietester.com/project/pro-nixie-tester/


And I'm searching for a pair of digital meters to go with it. I can live with a voltmeter that only goes up to 199V DC but 300V would be better. What I'm really unsure about is a digital ammeter that can handle at least 20mA at these high voltages. The precision should be at least a tenth of a mA (for working with IN-9/IN-13 at least).

Yes, I know I can go over to Harbor Freight and get a couple of cheap DVMs and cobble something together but I need a display large and bright enough for my lousy eyesight. A couple of DPMs with bright LEDs would be perfect and take up much less space.

A friend of mine bought a K40 laser cutter recently so I'd be able to cut an acrylic enclosure to match the PRO Nixie Tester.


Terry Bowman, KA4HJH
"The Mac Doctor"


“...the book said something astonishing, a very big thought. The stars, it said, were suns but very far away. The Sun was a star but close up.”—Carl Sagan, "The Backbone Of Night", Cosmos, 1980


gregebert

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May 17, 2022, 8:42:20 PMMay 17
to neonixie-l
IMG_0400.JPG

The meters in this power supply were purchased on Ebay for a few dollars each.
Voltmeter (lower) is 0-500VDC  . Ammeter is actually a 0-20VDC meter that measures the voltage-drop across a precision 1K resistor, to read 0-20mA.

Incidentally, the voltmeter measures what is delivered to the load so the ammeter does not affect the reading.

The middle meter, which is off for this range, measures 0-100mA directly.
Voltage is set via a small variac; current is set via 10-turn pot.

Mac Doktor

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May 17, 2022, 9:36:53 PMMay 17
to neonixie-l
On May 17, 2022, at 8:42 PM, gregebert <greg...@hotmail.com> wrote:

The meters in this power supply were purchased on Ebay for a few dollars each.
Voltmeter (lower) is 0-500VDC  . Ammeter is actually a 0-20VDC meter that measures the voltage-drop across a precision 1K resistor, to read 0-20mA.

Now we're gettin' somewhere. Can you point me in the right direction for the meters? Every time I search eBay or Aliexpress there are a zillion DPMs with voltages all over the place. My eyes start to glaze over...

Did you use a fixed resistor or a multi-turn pot? Wattage?

Sorry about the noob questions but my eyes aren't open enough today to glaze over in the first place. I know the theory but I'm having a hard time with math at the moment.

gregebert

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May 18, 2022, 12:02:33 AMMay 18
to neonixie-l
Here's a 500VDC meter:  https://www.ebay.com/itm/120990711589?hash=item1c2b9bbf25:g:Y~AAAOSw9KZiTu0p

If you go hunting around, you can find sellers that have a bunch of different ones. I've gotten addicted to these things and I've probably got close to a dozen of them in different things in the workshop to monitor voltage & current. 

Terry - I sent you an invite for the HVPS1 google group where you can get all the details of the power supply in the photo. I sold all of the PC boards to others (mainly for cost of shipping) who I hope got a chance to build their own. The 10-turn pot controls a current-limiter, so it runs at less than 1 watt. Take a look at the design report I posted on the forum and let me know if you have other questions.
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