From: "Malcolm Watts"
Date: Wed, 06 Sep 2000 22:15:24 -0600
Subject: Re: [TSSP] Low Q Values
>From Malolm... could use a bit of clean up but he was in a hurry to get
the data to this effort ;-)) - T.
==============================
further ado. I suspect Mark R. has a copy but maybe not.
I can't explain the results you've been seeing but I've
really only over glossed over the posts so've probably missed
something. Will have to study at more leisure. Meantime, I put
my beloved sig gen out of action a couple of months ago and to
my horror discovered that the LH4001 current buffer is now
obsolete and the recommended replacements for it are either
neither pin-compatible nor have the same delicious spec.
Believe it or not, it was actually sent to us here as a sample
from NS and since nobody else knew what to do with it or
expressed any interest I swooped and left it lying around for
five years until I built the generator. If I can't get another
(any chance you could check for me please? - I tried the web
with the results I've just recounted) I've decided to redo the
entire generator and build a discrete output stage to source a
more decent current and voltage up to 1MHz or so.
Cheers,
Malcolm
P.S. - I tried a quick attempt at attaching but failed so
dropped the three files into this message.
From: "Malcolm Watts"
To: malcolm
Date: Mon, 12 Aug 1996 16:35:42 +1200
Subject: myfiles
TEST NOTES ON MEASUREMENTS
**************************
(1) Signal Generator : Measured output impedance = 7 Ohms
resistive
over range of frequencies used in tests.
The generator was built early this year for the purpose of
coil
measurement. It has a fine tune control, and the output stage
uses
a National Semiconductor LH4001 current buffer (slew rate
125V/uS),
BW = DC to 25MHz (+-10V into 50 Ohms).
Output : 950mVRMS unloaded (output was adjusted where
appropriate
during the measurements).
A frequency counter with 1Hz resolution and calibrated is
built-in.
It should be noted that the internal impedance of the
generator is
going to lower the final Q readings somewhat. The error has
been
disregarded in the data tables although it may be significant
for
the smallest coils (as much as 10% !!!).
(2) Oscilloscope : LEADER 60MHz Digital Storage scope.
Estimated reading error : +-5% max. due to resolution of
graticule
and noise on pickup.
Y-Amp settings used were 10, 20, 50mV/Division.
FSD = 8 Divisions (generator and Y amp adjusted to give peak-
to-peak FSD
at resonance with generator set to highest possible output for
minimum
Y amplification).
-3dB measurements taken at 5.6 Divisions (70%).
(3) Inductance Measurement : Sencore LC35 LC Analyser
(4) Resistance Measurement : HP
Coil Resistances (measured) : closewound (h/d = 5) =
spacewound (h/d = 5) =
(5) Accuracy for frequency measurements : +-10Hz up to 500kHz
+-30Hz up to 1MHz
+-50Hz to 1.5MHz
Tolerance due mainly to noise of coarse tune control on
generator.
ALL tolerances noted above are ABSOLUTE WORST CASE. In most
cases, the
readings are claimed to be significantly better.
(6) MEASUREMENTS : There are 2 basic categories.
(a) Measurement of 2 basic coils whose h/d ratio was changed
from
5 to 0.56 during measurements (h/d error : +-1%).
Winding Diameter = 6.6"
Coil 1 was closewound with 0.56mm diameter enamelled
copper wire
Coil 2 was spacewound with 0.3mm diameter wire with a
pitch to give
approximately the same number of turns as Coil 1.
Coil 1 was unvarnished to facilitate recovery of the wire,
and Coil 2
was lightly spray varnished to hold the windings in place.
Two coils like this allowed a comparison between the winding
types over a
range of frequencies and also allowed measurements of the
disks (below)
at two h/d ratios as the disks were reduced in size.
Coil 1 (h/d=5) L = 57.45mH (error +-0.05mH)
Coil 2 " L = 56.6mH "
N (est) both coils approx. 1360 turns at h/d=5
For the measurements in this category, two terminals were used
: a sphere
of 9" diameter, and a toroid (outer diameter = 19.5" and tube
dia.= 4.5")
The sphere was mounted at heights of 0.7" and 7" above the
windings
and the toroid at heights of 0.7", 7" and 17.3".
Each coil was also measured for no-terminal frequency and Q
with top lead
about 2" long.
For measurements at h/d = 5 to 2 inclusive, the bottom turn of
the winding
was mounted 19.5 +-0.5" above the floor. For h/d = 1, bottom
turn started
26" from floor and for h/d = 0.56, 28.8" above the floor.
(b) With Coil 1 at h/d=4 and Coil 2 at h/d = 3, measurement
was made at
four different heights above the windings of a number of
20gauge
Aluminium disks, diameters : 200mm, 300mm, 400mm, 500mm,
600mm, 686mm.
Diameter measurement error = +-2mm max.
For each disk mounted at the lowest height above the windings,
the coils
were also measured with :
(i) the bottom turn of the coil mounted 19.5 +-0.5" above
the floor
where the rest of the readings were taken
(ii) the bottom turn mounted 13 +-0.5" above the floor (Fe
concrete)
Disk heights were : 0.7", 7", 11.3" and 16.9" above the top
turn.
From: "Malcolm Watts"
To: malcolm
Date: Mon, 12 Aug 1996 16:35:44 +1200
Subject: myfiles
COIL MEASUREMENTS
*****************
(a) Coils of varying h/d ratio. (frequencies in kHz)
NB - frequency has been rounded to the nearest 1kHz so the
tables could
be fitted in a reasonable space.
COIL1 | SPHERE | TOROID
| NO TERM | |
Height| | 0.7" | 7.0" | 0.7" | 7.0" |
17.3"
---------------------------------------------------------------
------------
h/d | f Q | f Q | f Q | f Q | f Q |
f Q
---------------------------------------------------------------
------------
5 | 190 351 | 159 300 | 149 317 | 179 299 | 128 290 |
121 269
4 | 224 393 | 184 347 | 172 318 | 152 292 | 146 316 |
138 286
3 | 276 389 | 221 356 | 205 341 | 178 301 | 171 323 |
163 291
2 | 367 353 | 284 326 | 262 339 | 222 288 | 216 322 |
207 283
1 | 600 285 | 438 267 | 401 299 | 330 233 | 327 261 |
316 256
0.56 | 890 182 | 644 220 | 587 243 | 476 208 | 477 227 |
465 226
---------------------------------------------------------------
------------
h/d = 4 with bottom turn 13" off floor : f = 222, Q = 363
h/d | 0.56 | 1 | 2 | 3 | 4 | 5
L (mH)| 4.02 | 9.0 | 20.75 | 33.2 | 45.6 | 57.45
COIL2 | SPHERE | TOROID
| NO TERM | |
Height| | 0.7" | 7.0" | 0.7" | 7.0" |
17.3"
---------------------------------------------------------------
------------
h/d | f Q | f Q | f Q | f Q | f Q |
f Q
---------------------------------------------------------------
------------
5 | 186 286 | 169 232 | 145 227 | 176 234 | 125 204 |
118 178
4 | 220 329 | 205 233 | 168 258 | 149 225 | 142 225 |
135 204
3 | 274 351 | 216 292 | 201 275 | 174 232 | 168 243 |
160 231
2 | 371 399 | 280 325 | 259 307 | 219 237 | 213 266 |
204 239
1 | 605 451 | 433 336 | 397 325 | 326 237 | 323 271 |
312 256
0.56 | 899 392 | 632 353 | 577 326 | 467 253 | 467 279 |
456 274
---------------------------------------------------------------
------------
h/d = 3 with bottom mounted 13" off floor : f = 272, Q = 339
h/d | 0.56 | 1 | 2 | 3 | 4 | 5
L (mH)| 4.2 | 9.05 | 20.7 | 33.1 | | 56.6
NOTES: I forgot to get inductance reading for h/d=4 for Coil 2
:(
: A reality check on Coil 2 (h/d=1) Q reveals that the
resonant
frequency measured is within 1% of that calculated
using the
measured inductance and Medhurst's self-capacitance
formula.
The Q gives an AC resistance of around 75 Ohms
including the
generator and coax and strap used to feed the coil. The
clear
message is : If you are using 100 Ohms+ in series with
your
coils to measure them, you are not doing them justice.
From: "Malcolm Watts"
To: malcolm
Date: Mon, 12 Aug 1996 16:35:46 +1200
Subject: myfiles
COIL MEASUREMENTS
*****************
(b) Coils of h/d = 3,4 with disks mounted at different
heights.
(i) h/d = 4 (closewound)
NOTE: the first column has the coil + disk mounted 6.5" closer
to the
floor. See Test Notes for winding heights off floor.
HEIGHT
| 0.7" | 0.7" | 7" | 11.3" |
16.9"
DISK(mm) | f Q | f Q | f Q | f Q |
f Q
---------------------------------------------------------------
----------
200 | 216.6 349 | 217.4 368 | 195.8 332 | 188.4 294 |
181.6 259
300 | 200.4 328 | 201.2 347 | 182.0 337 | 174.9 312 |
168.6 290
400 | 207.7 301 | 208.5 306 | 169.6 346 | 163.4 308 |
157.8 292
500 | 167.2 328 | 167.9 329 | 157.5 342 | 152.6 331 |
147.8 314
600 | 153.3 313 | 154.0 302 | 146.5 325 | 142.7 324 |
138.8 301
686 | 142.9 297 | 143.6 312 | 137.9 320 | 134.9 313 |
131.5 292
(ii) h/d = 3 (spacewound)
NOTE: the first column has the coil + disk mounted 6.5" closer
to the
floor.
HEIGHT
| 0.7" | 0.7" | 7" | 11.3" |
16.9"
DISK(mm) | f Q | f Q | f Q | f Q |
f Q
---------------------------------------------------------------
----------
200 | 260.9 296 | 262.1 332 | 232.2 283 | 222.6 262 |
214.4 249
300 | 237.6 313 | 238.6 306 | 213.9 289 | 205.4 267 |
198.0 244
400 | 214.5 278 | 215.4 287 | 197.7 260 | 190.6 250 |
184.2 239
500 | 193.5 254 | 194.4 249 | 182.5 257 | 176.9 256 |
171.9 232
600 | 176.1 238 | 177.2 253 | 169.0 248 | 164.9 232 |
160.8 196
686 | 163.5 221 | 164.5 166 | 158.5 244 | 155.6 232 |
152.2 217
NOTE : The Q of 166 for the largest disk in this table with
the coil mounted
for second column measurements appears to be in error.
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.