As has been pointed out in other postings to the thread, the
coefficient of coupling is important. Whatever flux from the primary
(driven winding) does not couple to the secondary will not induce
voltage in the secondary, and the measured turns ratio will be low as
a result. However, by measuring the inductance of the primary when
the secondary is open and again when it is shorted, and doing the same
with the secondary, you can find the leakage inductances and therefore
the coefficient of coupling, fairly accurately. (The second
measurement is really a check for consistency.) No need for xrays.
You could further improve the accuracy, I suppose, by including a
resistance value for each winding; ideally it would be the AC
resistance at the operating frequency. It will probably make for
easier calculations if you load the secondary very lightly for the
measurement.

But I'm still not seeing any need to know the number of turns, other
than for idle curosity. "I need to know because I want to"??

Cheers,
Tom

"Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote in message ...
....
After reading several followups so far, I'm getting the picture that it
would be easier to measure the voltage ratio. Rich suggested using a
DVM, but IIRC their AC bandwidth is limited, and drops off above a few
kHz or so. Rectifying the AC is an alternativce, but then it's not
accurate if the .6V diode drop is a considerable part of the rectified
DCV. An O'Scope seems the best way to measure, if it can be calibrated.
Actually, come to think of it, all that's needed is the ratio, not the
absolute V values.

One thing that I had in mind when I originated this idea was that, say
for instance, I'm measuring a trigger transformer for a xenon tube,
where the number of turns could be thousands. If I wound a few tens of
turns on it, the V ratio could be a hundred or more. That might be a
bit more difficult to measure than the inductance.

Thanks to all for the thoughtful responses. I'm going to have to try a
few experiments to see how these work.

............ Phil