On Sat, 5 Jun 2004 21:11:09 +0000 (UTC), "Reg Edwards"
wrote:

The voltage ratio of a transformer is the same as the turns ratio.
Therefore, wind ten turns around the inductor and measure the voltage
at the output when a known voltage is applied to the inductor.

Norm Strong

====================

Agreed. That's about the best he can manage. But what is not known is the
coefficient of coupling between the two coils. They are not wound in the
same volume of space or anywhere near to it. One is entirely outside the
other.

If the outside coil has a coefficient of coupling of 0.5 with the inside
coil then it is equivalent to a coil with only half the number of turns.

The arithmetic is simple. But what the coeff of coupling might be is
anybody's guess without knowledge of ALL dimensions of BOTH coils. Ask your
dentist if you could borrow his X-ray machine for the day. Even then a
hefty treatise involving higher mathematics on how to calculate the
coefficient of coupling between two coils would be essential.

All one knows is that the turns error, possibly very large, must lie on the
low side of the true value.

Its just occurred to me that with access to a precision X-ray machine or
electron microscope it may be possible actually to count the number of
turns. Try NASA.

How many Henrys is the thing anyway?
===
Reg.


A lot of our larger battery charger transformer designs have primaries wound
outside with the secondaries closest to the core. It is quite a common
technique, even on some of the smaller stuff we use.

Peter

--
Peter & Rita Forbes

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