I have question about R L Mathematics
 

On 1/30/2014 1:14 PM, John S wrote:
On 1/30/2014 9:33 AM, amdx wrote:
(snip)

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

Hi, Mike -

I would like to buy a couple to experiment with and, possibly, learn
something.

How many $ do you want and how do we connect?

Thanks,
John S

Hi John,
My address is good.
These are 2" ceramics, 1/16", they resonate around 1.2MHz as I recall.
We bonded them to 1/16" aluminum for approximately a 660kHz transducer.
We drove them at antiresonance, where they measured around 20 ohms.
We drove them continuous at 250 watts in an ice bath and 1000 watt pulsed.
Send me an email.
Mikek

I have question about R L Mathematics
 

On 1/30/2014 1:17 PM, Fred Abse wrote:
On Wed, 29 Jan 2014 20:26:16 -0800, Jeff Liebermann wrote:

You really want a vector impedance meter:

He's actually doing what a vector impedance meter does - the hard way.

Attempting to do, and not the hard way the cheap way.

I built a tight unit this morning, 3.9% or 7.4% error measuring a 3090
ohm resistor, depending on which way I swap the scope probes*.
The measurement didn't change from 100kHz to 10MHz, so now I think
I've tamed the strays. When I get new probes and if they act identical,
I'll work on accuracy.


A vector voltmeter might be of more use in Mike's case. More versatile.

I have one one the back burner. I want to try to work the kinks out of
this, see if I can make an easy to build device for someone that has a
scope and frequency counter, so they could check C, L or Z, at
frequencies up to 10 MHz.
Simple, at this point I have panel mount BNC, a 50* ohm resistor, small
piece of perf board and wire.

Here's a couple of pictures to show the simplicity.
The top picture shows the resistor under test.
The bottom shows the sense resistor.

http://s395.photobucket.com/user/Qma...10be8.jpg.html

http://s395.photobucket.com/user/Qma...cde6b.jpg.html


The sense resistor must be mathematically subtracted. A 50 ohm sense
resistor
with 15pf scope probe in parallel is changed by less than 0.1 ohm, at 10MHz.

* new probes on the way.
**I had a 47.5 ohm 1% resistor.

I have question about R L Mathematics
 

On 1/30/2014 3:19 PM, Fred Abse wrote:
On Thu, 30 Jan 2014 14:31:58 -0600, amdx wrote:

Here's a couple of pictures to show the simplicity. The top picture shows
the resistor under test. The bottom shows the sense resistor.

http://s395.photobucket.com/user/Qma...10be8.jpg.html

http://s395.photobucket.com/user/Qma...cde6b.jpg.html

My browser doesn't support some of the more esoteric scripting that
Photobucket uses.

Better to post to ABSE, I can actually read that.


Took me three tries, but I got it all over there.
Mikek

I have question about R L Mathematics
 

On 1/30/2014 3:57 PM, Fred Abse wrote:
On Thu, 30 Jan 2014 15:37:45 -0600, amdx wrote:

Took me three tries, but I got it all over there.

All I see is the URLs, but with the enough information to download with
wget.

Please tell me those wire gimmicks that hold the probes aren't enameled
magnet wire. They look awful dark, here.

Nope they're stripped clean with a great tool.
I'll post it under the same thread in abse.
Got when I worked at a motor rewind shop 32 years ago.
Mikek

I have question about R L Mathematics
 

On 1/30/2014 6:41 AM, W5DXP wrote:
On Wednesday, January 29, 2014 6:20:16 PM UTC-6, amdx wrote:
This evening I'll wind a 55uH coil and find a 3,072 resistor. I'll put
these in series and see how it measures compared to my lossy ferrites
beads on a cable.

A coil of that large size will exhibit transmission line characteristics that will render the lumped-circuit model inaccurate because the current into the coil will not be equal to the current out of the coil. Better to use the distributed network model which is closer to Maxwell's equations. Here is an inductance calculator that will yield more accurate results for coils that are greater than ~15 degrees long electrically. Using the axial propagation factor (Beta) of the the coil, one can calculate how many degrees it occupies. Then using the characteristic impedance (Z0) of the coil, one can analyze the circuit like a transmission line using the distributed network model. If you will describe the characteristics of the coil in detail (total turns, length, wire size, etc.) I will do the analysis for you.
--
73, Cecil, w5dxp.com


I used an adjustable inductor I made with 7/16 polypropylene tube, wound
with 660/46 wire and a ferrite rod I slide in and out to set the
inductance. The Q was 250 at 3Mhz on my Booton 260.
Mikek

I have question about R L Mathematics
 

On Thursday, January 30, 2014 6:39:10 PM UTC-6, amdx wrote:
... a ferrite rod I slide in and out to set the inductance.

Sorry, I don't know how to model the ferrite rod inside
the coil.

I have question about R L Mathematics
 

On Thu, 30 Jan 2014 13:19:00 -0800, Fred Abse
wrote:

My browser doesn't support some of the more esoteric scripting that
Photobucket uses.

Better to post to ABSE, I can actually read that.

Is that
alt.binaries.schematics.electronic
or
alt.binaries.schematics.electronics
I never could figure out which is the correct newsgoup.

--
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 question about R L Mathematics
 

On 1/30/2014 9:03 PM, Jeff Liebermann wrote:
On Thu, 30 Jan 2014 13:19:00 -0800, Fred Abse
wrote:

My browser doesn't support some of the more esoteric scripting that
Photobucket uses.

Better to post to ABSE, I can actually read that.

Is that
alt.binaries.schematics.electronic
or
alt.binaries.schematics.electronics
I never could figure out which is the correct newsgoup.


I posted to alt.binaries.schematics.electronic
but I was not feeling up to figuring out how to post my pics properly.
I've done it before but these didn't post as I wanted.
Do you have a problem viewing photobucket pictures?
Did you get the 3B7 scans?
Life in my city should return to normal tomorrow, temps going up to 61*.
Mikek

I have question about R L Mathematics
 

On 1/30/2014 1:46 PM, Fred Abse wrote:
On Thu, 30 Jan 2014 13:30:13 -0600, John S wrote:

On 1/30/2014 1:17 PM, Fred Abse wrote:
On Wed, 29 Jan 2014 20:26:16 -0800, Jeff Liebermann wrote:

You really want a vector impedance meter:

He's actually doing what a vector impedance meter does - the hard way.

A vector voltmeter might be of more use in Mike's case. More versatile.


Where is one available and what would it cost?

There are a few HP8405 vector voltmeters on Ebay.

Be warned, the "probes" are actually miniature sampling heads, and can
easily be ruined by overvoltage.

They did come with a set of accessories, but, judging by Ebay, these will
likely have been split off, and sold separately.


Thanks. I'll look into it.

I have question about R L Mathematics
 

On 1/28/2014 1:03 PM, amdx wrote:
I have beads* on a coax and want to know the R and the L.
I have measured the R at 3.85MHz, It is 3,350 ohms.
I have also measured the phase shift, voltage leading
by 17ns. The period of 3.85Mhz is 260ns.

I want to calculate the impedance of the reactance.

Can anyone solve this for me?
I would like to see the math, because I want to measure again
at 7.5MHz.

My first step was to find the phase angle, 23.5*.
Do we agree there?

Thanks, Mikek


* it is actually a bit more than beads. Years ago, we were sent a box of
ferrite potcores, the cores arrived broken. I slide 42 broke halves onto
a piece of RG59, and now I'm measuring it.


Hi, Mike -

I have reviewed your pictures and re-read the posts and I have a couple
of new comments.

* I don't know how you verified that your probes are a problem, but I
suggest applying the same signal to both, recording the results,
swapping channels, and see if the problem follows the probes or not. If
the problem follows, it's the probes. If not, it's the scope channels.

* The ll feet of coax alone will cause almost 11ns of delay. Since you
have it coiled on each end, the delay will be more than that. This
leaves us in an even worse situation to explain high R and low L.

* If you, by any chance, have another 11-feet piece of coax without the
cores, try measuring that.

Good luck.

John S