# Re: How To Measure NST Coupling

```Original poster: "Dmitry (father dest)" <dest@xxxxxxxxxxx>

Hallo Barton,

Sunday, March 05, 2006, 9:30:50 AM, you wrote:

> I measured the NST today with described method.
> Vsec/Vpri = Applied Vpri voltage = 12160/120 = 101.333 = x1
> Vpri/Vsec = Applied Vsec voltage = 99.5/12010 = 0.0082847 = x2

you are trying to measure coupling at full rated voltage, then why when
you applied voltage to secondary your primary V was only 99.5V? you
must apply enough Vsec to get 120V on primary, so your present data is
useless, coz as you can see from previous msms, coupling at 100 and at
120 volts are not the same.

> k = sqrt(x1*x2) = 0.916 (about 10% err if compared to V, I measurments).

10% error? how did you calculated this? % )))
"Looks like for my 12/60, k is at 0.938 at rated voltage."

0.916/0.938=97.65%, so "error" was only 2.345% : D

> I believe the previous method is accurate. My reason is due to the
> simulation resolved in the transformer model (when comparing the
> different k measurements). That is my only basis for accurate
> resolution.

for me it only means that previous method is matched well with your
model - no more.

"B: I used the method given and it worked fine.
d: how could you know that it`s fine - have you compared it with any
other 100% valid method? : )
B: It is."

can i ask - what was that other 100% valid method?
i have nothing against i/i method in case of current limited trannys -
just wanna know : )

-----
Let the bass kick! =:-D

```