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RE: [TCML] NST Measurements



Hi Bart,

As often as I have dispensed the same advice to measure and feed the mains voltage into the NST secondary and measure the primary to determine the sec/pri ratio, I don't recall ever having actually done that to mine.  So, I just pulled out a 15/30 and a 15/60 NST.  

The 15/30 measured a ratio of 153X, so assuming a 120V primary, predicts a 18.3kV secondary.

The 15/60 measured a ratio of 145X, so assuming a 120V primary, predicts a 17.4kV secondary.

The meter that I used is a simple Fluke DMM, not RMS.  But given that the NST is going backwards, I wouldn't think that it's getting near saturation and the associated waveform weirdness.  Unfortunately I don't own a HV probe that I would trust to measure it in the normal operating sense.  Have you done this and gotten closer to the faceplate voltage rating?

Regards, Gary Lau
MA, USA


> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of bartb
> Sent: Sunday, January 18, 2009 5:37 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] NST Measurements
> 
> Hi Jeremy,
> 
> How you perform a measurement depends largely on the equipment you have
> on hand and what it is you want to identify. So my first question is
> what meters do you have hand to make measurements? Obviously, a HVac
> probe would be ideal, but not absolutely necessary to simply identify
> rough specs. If you have say only a digital rms meter handy, hook up
> 120Vac to the output side and measure voltage on the primary. This will
> do fine for identifying your turns ratio (Vout/Vin). Then you can just
> figure wall plug AC volts x turns ratio for the output. Current more
> complicated.
> 
> If you want to look at "more" and get to know the transformer for what
> it really is, two meters are helpful. One to read current and the other
> to read voltage along with a HV probe. I'm not a big fan of reverse
> wiring the transformer to gain transformer characteristics other than
> the basic turns ratio. When normal current is flowing, it will be
> different from the reverse wired situation because the secondary voltage
> applied is never the output volts (but some far lower voltage). If you
> could, a hv probe would be needed. But at that point, you may as well
> feed low voltage high current to the primary for ease of measurements.
> 
> So again, what equipment do you have on hand?
> 
> Bart
> 
> Jeremy wrote:
> > Ok, wait, so how exactly do you guys propose measuring NST outputs for
> dummies? i have  9kV 30mA unit as well as a large unlabelled unit atm, and the
> unlabelled one arcs at over half an inch so i'm guessing it's at least 15kV 60mA. I
> need the measurement on the unlabelled unit. I was thinking of using a 10V input to
> the NST, then further stepping down the output by 20x to be measured by a
> voltmeter. Is this workable? (all components rated at 240V input)
> >
> >
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