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Measuring Secondary Coils
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From: chris.swinson [SMTP:chris.swinson-at-zetnet.co.uk]
Sent: Friday, August 21, 1998 12:31 PM
To: Tesla List
Subject: Re: Measuring Secondary Coils
Hi All,
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: 'Tesla List' <tesla-at-pupman-dot-com>
Date: 21 August 1998 05:45
Subject: Measuring Secondary Coils
>
>----------
>From: RWB355-at-aol-dot-com [SMTP:RWB355-at-aol-dot-com]
>Sent: Thursday, August 20, 1998 5:18 PM
>To: fwd
>Subject: Re:Measuring Secondary Coils
>
>---------
>From: chris.swinson [SMTP:chris.swinson-at-zetnet.co.uk]
>Sent: Wednesday, August 19, 1998 7:44 AM
>To: Tesla List
>Subject: Secondary Frequency
><SNIP>
>
>Hi Chris, all !!
>
>Chris
>
>I hope you are not thinking of just "plugging" a capacitor and/or
inductance
> meter across your secondary coil and then just reading what the meter
tells
> you. That doesnīt work !! The measuring frequency of these meters is way
too
> low to give an accurate reading of the inductance (capacitance) the coil
has
> at "our" operating frequencies. Typical DMMīs run at about 200Hz better
ones
> at 400Hz or 1000Hz. I donīt know, however, if there are RF "adjusted"
meters
> that would be able to really measure the values correctly.
>
Humm, I've not had problems like this before, I know that DMM's can lie
though at times. Only thing which troubles me is the fact I have a current
limiting chart which tells you in steps of 1 amps the inductance. I tried
this out with a few TR's and the meter aggreed with the table which suggests
that the meter is correct. I have treid lots of calculations and they all
say about 30mH, But the meter says 11mH.
>Otherwise, the only way I think you could do it properly, would be to
connect
> a frequency gen and an O-scope to the coil via a Wheatstone bridge. That
way
> you could find the frequency at which the coil resonates, but you would
still
> have to calc the (unknown) inductance/ capacitance part of the bridge
(read:
> your coil). So you would be back to square one.
> I suppose you stepped into the same bear trap I did and used wire length
as a
> grounds for your calculations. And as many coilers have proven (and if you
> think about it is pretty logical, too) the 1/4 wave theory will sink you
like
> a leaky submarine.
>
Well I know the running frequency is 200Khz for a fact, as It's been scopped
out at that frequency. Perhaps some one clever can calc what inductance
will match that frequency, then I'll know which reading is right. I have my
hunch that the 30mH is right.
>Regards and safe coiling,
>Reinhard
>
Thanks :-)
Chris
>
>