Re: More Coupling...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi John 

Tesla list wrote: 
>
> Original poster: "John H. Couture by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <couturejh-at-worldnet.att-dot-net> 
> Bart - 
>
> Coilers assume that measured values are "sweetly" accurate but that is not 
> correct. All measured values have a probable error. The problem is how do 
> you determine that error? It is obvious that inputing incorrect values for 
> the computer inputs will make the computer outputs incorrect. In the past I 
> have found that before making any tests it is an advantage to find the 
> approximate value for the measurement by computer or by calcs. I then make 
> several tests for the same parameter. I also use more than one test method 
> for the same parameter. This usually guarantees a close agreement in values 
> which also gives me some number differences from which I can devise an 
> approximate probable error.

Yes, understood. BTW, when I say sweetly accurate, that just means to me that I
am very impressed with a calc to measured value, nothing more. There's inherent
error in measurement and calcs and that must be understood. You bring up some
good test practices here. 
>
> Fortunately there is more than one test method for the coupling. Have you 
> compared the mutual test for finding the coupling with the coupling tests 
> mentioned on the List?

No. As is typical with many coilers (myself included), I can only measure with
the equipment available to me. I can't do the frequency test, so have stayed
with current testing procedures. 
>
> You may also want to try the mutual inductance test as shown in my TC Design 
> Manual. This is the same test as you are now doing except that it is more 
> accurate. A variac and lamp or resistor can be used to set the current. Non 
> linearity is not a factor because only one current value is used. The 
> accuracy then is dependent only on the digital voltmeter which is inherently 
> very good. 
>
> The current is adjusted to 2.653 amps and the mutual inductance in 
> microhenries is read directly off the digital meter. The meter is actually 
> showing millivolts. No calculations are required.

I haven't seen this particular test before, but it sounds practical and it
seems I have the equipment for this. I'm glad you brought up the non-linearity
of the lamp. I wasn't sure how this would affect a measurement. I think I'll
try this at some point. This will be good as long as the current is stable. 

I like Terry's method with concentric readings of amps and volts. This takes
the current change out of the math (except speed of meter readings with current
changes). Also, his tests showed how the current "did" change during the
testing. 

Thanks for the ideas, 
Bart