# Re: High frequency impedance of a neon sign transformer

• To: tesla-at-grendel.objinc-dot-com
• Subject: Re: High frequency impedance of a neon sign transformer
• From: jim.fosse-at-bdt-dot-com (Jim Fosse)
• Date: Thu, 04 Apr 1996 06:56:01 GMT
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```tesla-at-grendel.objinc-dot-com On Wed, 3 Apr 1996 20:01:01 +0700, you wrote:

Ed and Malcolm,

just to confuse the issue, I measured my "air core" 15KV -at-60mA 1/2
neon secondary:) I wasn't up to trying to measure it iron core
tonight.

I used a 10K series resistor to measure the current and my Simpson 260
to measure the voltage across that 10K resistor. I don't have the
frequency response for my Simpson. Any one?

Rdc	=	2600 ohms for this coil.

applied	measured	Z
--------------------------------------------------------------------------------
60 hz	1Vrms  	0.68Vrms		4.7K
100hz	1V	0.6V		6.67K
1Khz	1V	0.18V		45.6K
10Khz	1V	0.1V		90K
100Khz	1V	0.2v		40K

Please, do note the rise in voltage between 10K and 100K, I measured
the self resonance frequency at 33.646KHz with a 10K ohm resistor and
at 34.559KHz with a 100K ohm resistor. Also note that when we go from
100 Hz to 1KHz  the impedance go from 6.67K to 45.6K instead of 66.7K!
Likewise from 1KHz to 10KHz we only get a 2:1 Z increase. It then
drops above the self resonance freq.

```