Re: Measuring neon transformer current rating

Tesla List wrote:
> >From ccudahy-at-calumet.yorku.ca Thu Dec 12 14:41:40 1996
> Date: Thu, 12 Dec 1996 12:27:02 -0500 (EST)
> From: Chris Cudahy <ccudahy-at-calumet.yorku.ca>
> To: tesla-at-pupman-dot-com
> Subject: Measuring neon transformer current rating
> Hi all..  I have a neon sign transformer that I got a while ago. It seems to
> work fine (I've been running a jacobs ladder off it occasionally) and I'd
> like to use it in a TC system, but it doesen't have a plate on it, and I
> have no idea how much current it puts out.
>  Is there any good way to measure it's current rating ?
> It's pretty large (23cm x 10cm x 14cm) with 4cm long, 3.5cm dia ceramic
> insulators on the ends - anyone have a similarly sized neon & could
> hazard a guess ?
> I'm planning on running with a 0.009ufd cap off it.
> Thanks,
> Chris
> +--------------------------------------------------------+
> |Chris Cudahy             | B.SC. CS/Math - getting there|
> |ccudahy-at-calumet.yorku.ca | Swim Bike Run Colapse        |
> |http://www-home.calumet.yorku.ca/ccudahy/www/home.htm   |
> ---------------------------------------------------------+


Junked neon transformers returned for warranty credit typically have
their nameplates removed. An easy way to get the voltage and current
ratings is via a 6.3 VAC filament transformer and a 100 Ohm 2 Watt
wirewound resistor. You can verify that both halves of the neon are
working by drawing an arc to the transformer case from either output. To
actually measure the current and voltage some additional measurements
are necessary.

Connect a VOM across the ouput of the neon, and set the voltage for
about 1000 volts. Apply 6.3 volts from the filament transformer to the
primary of the neon. If both secondaries are working, you should get
about the following readings. (Vout = Vmeasured*(120/6.3) ~

  	          Approx. Vmeasured
	 Full       With 6.3VAC
	Voltage:    on Primary:
	 6000		315
	 7500		394
	 9000		473
	12000		630
	15000		788

Connect a 100 Ohm 2W wirewound resistor across the outputs of the neon
transformer, and also hook a VOM across the resistor. MAKE SURE YOU HAVE
SOLID CONNECTIONS at all points! Set the VOM to read about 0-10 volts,
and turn the transformer on. The neon will current limit under these
conditions, allowing you to measure the short circuit current. The
transformer current is the found by taking the voltage across the
resistor and dividing by 100 (Iout = Vout/R). 

   Approximate	      Transformer
   Voltage AC:       	Current:
	 2		20 MA
	 3		30 MA
	 6		60 MA
	12             120 MA

However, don't try this with a non-limiting transformer!!

Safe coilin' to ya!

-- Bert --