RE: [TCML] Measuring Amperage in Neon Discharges.

["Lau, Gary" <Gary.Lau@xxxxxx>]

I think Harvey was looking to measure the current drawn by the operating tube, not the NST short circuit current.  Inserting the meter in series with the circuit is perfectly fine, just as long as the meter is set to measure current and not left on the voltage setting.

However, the meter may not read a useful value.  Unless the meter is an RMS-calculating type, it assumes that the current waveform is a sine wave and just reads 0.707 times the peak value.  Since the load current is zero until the ionizing voltage is reached and is non-linear beyond that point, the actual RMS current will be something very different, and it's not clear that RMS is what is needed, anyway.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Jon Danniken
> Sent: Monday, December 14, 2009 8:22 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Measuring Amperage in Neon Discharges.
> 
> Harvey Norris wrote:
> > Question; Can I simply put a common multimeter in series with a neon
> > tube illuminated by a 30 ma current limited NST secondary, to record
> > that secondaries amperage output? Do I need a special digital meter
> > to do this?
> 
> Doing so will expose the meter to the full voltage produced by the NST until
> the gas(ses) inside the tube ionize and conduct.  This will likely not only
> destroy your meter, but may energize whatever table the meter is sittting
> on, providing a dangerous situation also for you.
> 
> The standard method of determining a NSTs output current is across a dead
> short.  Connect your current meter in series from one output of the NST to
> the other.  Because the NST is a current limited transformer, you will be
> measuring the "short circuit current," which is how they are rated, and in
> this test situation the output voltage will be low (still isolate the meter
> from your workstation and yourself, for safety).
> 
> Jon

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