On 1/29/2014 10:26 PM, Jeff Liebermann wrote:
On Wed, 29 Jan 2014 09:45:51 -0600, amdx wrote:
On 1/29/2014 9:04 AM, Jeff Liebermann wrote:
I have a feeling you didn't look at any of my pretty pictures, I think
at least one layer of fog should have dissipated if you did.
They're really pretty.
http://s395.photobucket.com/user/Qmavam/media/TheBoardwithnotes.jpg.html
http://s395.photobucket.com/user/Qmavam/media/TheBoardDrawing.jpg.html
I clicked, I looked, I saw, I failed to understand, I blundered
onward. What did I miss?
Probably not much. :-(
Very simple concept, Measuring current by use of a sense resistor.
Then comparing voltage to current to get impedance.
You really want a vector impedance meter:
http://www.ebay.com/itm/181276724052
I have recently acquired an HP 3570A Network analyzer and a 3330B
synthesizer that are GPIB connected to a computer with custom software.
It has not been powered for at least 10 years. The only problem I know
about is the computer cmos battery most likely has failed.
I've had it a couple months now and have not got it setup or attempted
any use. I need to figure out what to do about the computer first. I
don't have the original software disc, so I need to copy the program
first thing.
Yeah, I know it's an antique. There are probably much better models
available today, but not at the price. I had one at a previous
employer and used it for measuring almost everything. 0.5 to 110 Mhz.
I've been looking for a broken one (because I blew up the one I was
using often enough to be familiar with the repair procedures) but
can't seem to find one in my price range (i.e. free). Make sure it
comes with the probe and power cord as both are difficult to find.
Note that I'm suggesting that you measure the inductance with a single
wire going through the cores,
I'm doing that now, only with 42 halves. I can try it with one, but I
question with my "setup" will resolve that inductance.
Never mind. You won't see it. At the time, I was trying to correlate
the measured value with the theoretical Al. However, since the cores
are not being used in the normal manner, that's not going to work or
yield any useful results. Might as well measure the whole string at
once.
Do you need any potcores?
No thanks. I gave smoking the stuff in college. You might be able to
sell them in Colorado.
Since you have used "ohms-guesser" I guess I need to ask, What is that?
and does it use ac or dc for the measurement?
An ohms-guesser(tm) is a Harbor Freight DVM or equivalent. Usually
sells for $5 or less. Capable of producing wrong values to at least 3
1/2 digit accuracy. I usually have several available for the
inevitable visitors that roll into my parking lot wanting to borrow a
meter to fix their vehicle electrical system. Ohms-guessers use DC
current to measure resistance. There is also the volts-guesser and
amps-guesser which offer similar features and lack of accuracy.
You may have figured out, I'm not using this type of ohms guesser.
The number is (obviously) wrong because nowhere in your
circuit is anything resembling a resistor of that high a value.
I'm sure you understand that ferrite beads on a transistor lead, show
up as a resistive and inductive. Why is this different?
Here's a pdf with a graph page 4 right side showing R, X, and Z.
Hand picked to show what I want it to! Although I should have secretly
altered the frequency range.
http://www.vishay.com/docs/ilb_ilbb_enote.pdf
ARGH! I goofed. I forgot how ferrite really work and was assuming
that it represented a pure inductance. Please ignore everything I
wrote about the resistive component. I tried to find a reactance vs
frequency graph for the 3B7 material and failed. Maybe later tonite.
I'm buried in broken machines and an office in desperate need of
untrashing. Thanks (grumble).
Incidentally, consider yourself off the hook for the MFJ-1800 yagi
fiasco if you promise not to tell anyone how badly I messed up here.
My deed here has been accomplished, I now officially close this thread.
yippee, yahoo, hallelujah, praise be to any omnipotent powers.
I'm in Fl. where people are acting like the end is near.
Huh? Are they expecting Florida to sink into the ocean under the
added weight of the snow?
We are slightly below freezing and businesses are closing, schools out.
The weather men are have fits of frenzy. If I was back in Michigan, we
would be happy it got warmer, because we were getting tired of
starting the car at 7* in 8 inches of snow.
Mikek
In the People's Republic of Santa Cruz, it has been mostly 60-70F
highs and 35-45F lows for most of the alleged winter. Quite pleasant
and comfortable. The problem is that we've had less than an inch of
rain this season, where normal would be about 15-20 inches by this
date. The forest looks awful with dead trees and shrubbery
everywhere. Looks like we're going to have a severe drought here.
Even worse is the lack of snow for skiing. Right now, I could use
some snow or rain.
-- Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com Santa Cruz CA 95060
http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I have found through some tests and exchanges here that the mechanics of
my "setup" work fine below 1MHz or a little higher. But I think, strays
are causing some problems when I go higher in frequency.
I should get my new probes today and I'll be working at tightening
up the circuit and maybe adding shielding.
I built this "setup" as as duplicate of the one I used, I tried to use
it at higher frequency and I should not have.
When I was working with ultrasonics, our standard frequency was around
660 kHz. We used this daily to characterize piezo transducers to
calculate matching to an amplifier.
I sure wish the company made some money, I really enjoyed that job.
btw, Need any 2" disc piezo ceramic discs 1/16" thick PZT-8 material?
I have a few other sizes also.
Do you know any fun things I could do with them, besides give people
shocks.
Thanks, Mikek