[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: More Coupling...



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

Hi Paul, All, 

Checked the meter today against a scope at work. If there was a
discrepency, I couldn't see it. Also checked it against 2 other calibrated
DMM's = Idetical (wow, good calibration). So I figured the meter is reading
correctly. No doubt, some dimension must be off. So I took the coil apart
today and started a thorough check, then I saw it! I was tapped at 10.6
turns, not 11.6. Ahhhhh, that makes a difference and in the right direction. 

Well, I retapped to 11.6 turns and decided to set up and go through the
test again. Still had 1 DMM so checked current at +2, 0, and -2. The
current was holding well at 10.07V (hair dryer). 

Here are the results: 

(p - s)    SecV      M        K 
- 2.00    1.582    416.7    0.135 
  1.75    1.618    426.2    0.138 
  1.50    1.675    441.2    0.143 
  1.25    1.723    453.9    0.147 
  1.00    1.761    463.9    0.150 
  0.75    1.814    477.8    0.155 
  0.50    1.848    486.8    0.158 
  0.25    1.896    499.4    0.162 
  0.00    1.932    508.9    0.165 
+ 0.25    1.989    523.9    0.170 
+ 0.50    2.030    534.7    0.173 
+ 0.75    2.078    547.4    0.177 
+ 1.00    2.121    558.7    0.181 
+ 1.25    2.161    569.2    0.185 
+ 1.50    2.204    580.6    0.188 
+ 1.75    2.246    591.6    0.192 
+ 2.00    2.282    601.1    0.195 

Well, that does change values closer to the predicted and the cause was the
primary off by 1 turn. However, there is still a climb in error % as the
coupling is increased. 

Update to your previous example, 

      bart     acmi    error% 
+2    0.135    0.141    4.44% 
 0    0.165    0.178    7.88% 
-2    0.195    0.215   10.26% 

I'm beginning to wonder if this error increase with coupling is a result of
a flat primary field with a perpendicular secondary and not a primary
current change. The deeper the secondary protrudes into the primary, the
higher the error. 

Paul, something to keep in mind about my primary is it is very flat and
evenly spaced throughout. When I measure inner turn primary distance, I
measure at start of the inner turn and directly across (c-c measurements).
I use 8 runners and measured out each runner primary position to ensure
equal incremental steps. All in all, it's a very nice flat primary for this
type of measurement. There are about 2 turns unused after the tap, but this
shouldn't affect these readings. 

Maybe if I've been nice (vs. nauty) this year, Santa will bring me an LCR
and further verify inductances. 

Take care, 
Bart