I have question about R L Mathematics

[Fred Abse]

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.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[amdx]

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/Qmavam/media/Imptop_zps58e10be8.jpg.html

http://s395.photobucket.com/user/Qmavam/media/ImpBottom_zps085cde6b.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.

 

[Fred Abse]

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/Qmavam/media/Imptop_zps58e10be8.jpg.html

http://s395.photobucket.com/user/Qmavam/media/ImpBottom_zps085cde6b.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.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[amdx]

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/Qmavam/media/Imptop_zps58e10be8.jpg.html

http://s395.photobucket.com/user/Qmavam/media/ImpBottom_zps085cde6b.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

 

[Fred Abse]

On Wed, 29 Jan 2014 19:37:47 -0600, amdx wrote:

I measured a 55uH inductor and 3090 ohm resistor in series, 3.85MHz
and got 2778 ohms 19.9* phase difference. The calculated numbers are Z =
3,364 and I don't know how to calculate the phase angle.

Re(Z)=3090
Im(Z) = 2 * pi * 3.85*10^6 * 55*10^-6

Phase angle = arctan (Im(Z)/Re(Z)


General rule: If Z = a +jb,
Then phi = arctan (b/a), and mag(Z)=sqrt(a^2+b^2)

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[Fred Abse]

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.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[amdx]

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

 

[Jeff Liebermann]

On Thu, 30 Jan 2014 13:19:00 -0800, Fred Abse
<excretatauris@invalid.invalid> 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 jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[amdx]

On 1/30/2014 9:03 PM, Jeff Liebermann wrote:

On Thu, 30 Jan 2014 13:19:00 -0800, Fred Abse
excretatauris@invalid.invalid> 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

 

[John S]

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.

 

[John S]

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

 

[amdx]

On 1/31/2014 6:49 AM, John S wrote:

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.

Yes that's what I did, problem follows the probes. I'm not surprised,
I have done a major repair to the metal housing that was broke in two
pieces. I seem to have ruined a solder tip soldering the metal the
housing is made off. The probes are at least 30 years old. I didn't
receive my new probes yesterday (as told) maybe today.

* 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.

I'll have to check that, an see if my "setup" verifies that.

This
> leaves us in an even worse situation to explain high R and low L.

Ya, hmm.
I did find a data sheet for 3B7 but the loss graph only goes to 500kHz.
I'll take the book with me to work and see how the losses of this
material compare to others. Don't know if it is high loss or low loss.

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

I will be busy all weekend, working for a living, I hope I can try
something sooner, but it might be next Tuesday.

Good luck.

John S

 

[John S]

On 1/31/2014 7:21 AM, amdx wrote:

On 1/31/2014 6:49 AM, John S wrote:
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.

Yes that's what I did, problem follows the probes. I'm not surprised,
I have done a major repair to the metal housing that was broke in two
pieces. I seem to have ruined a solder tip soldering the metal the
housing is made off. The probes are at least 30 years old. I didn't
receive my new probes yesterday (as told) maybe today.

Okay. Use one probe to measure both amplitudes. Use both probes to
measure the phase (at zero-crossing only) while ignoring the amplitudes.

Otherwise, use your new (calibrated by you and verified by you) probes.

* 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.

I'll have to check that, an see if my "setup" verifies that.

This
leaves us in an even worse situation to explain high R and low L.

Ya, hmm.
I did find a data sheet for 3B7 but the loss graph only goes to 500kHz.
I'll take the book with me to work and see how the losses of this
material compare to others. Don't know if it is high loss or low loss.

I would not expect 3B7 to be of significant inductance at your frequency
of interest. It might be instructional to insert the coax into a piece
of conduit of the same length and measure it.

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

I will be busy all weekend, working for a living, I hope I can try
something sooner, but it might be next Tuesday.

I understand. I don't mean to push you.

John S

 

[amdx]

On 1/31/2014 8:44 AM, John S wrote:

On 1/31/2014 7:21 AM, amdx wrote:
On 1/31/2014 6:49 AM, John S wrote:
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.

Yes that's what I did, problem follows the probes. I'm not surprised,
I have done a major repair to the metal housing that was broke in two
pieces. I seem to have ruined a solder tip soldering the metal the
housing is made off. The probes are at least 30 years old. I didn't
receive my new probes yesterday (as told) maybe today.

Okay. Use one probe to measure both amplitudes. Use both probes to
measure the phase (at zero-crossing only) while ignoring the amplitudes.

Otherwise, use your new (calibrated by you and verified by you) probes.


* 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.

I'll have to check that, an see if my "setup" verifies that.

This
leaves us in an even worse situation to explain high R and low L.

Ya, hmm.
I did find a data sheet for 3B7 but the loss graph only goes to 500kHz.
I'll take the book with me to work and see how the losses of this
material compare to others. Don't know if it is high loss or low loss.

I would not expect 3B7 to be of significant inductance at your frequency
of interest. It might be instructional to insert the coax into a piece
of conduit of the same length and measure it.


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

I will be busy all weekend, working for a living, I hope I can try
something sooner, but it might be next Tuesday.

I understand. I don't mean to push you.

John S

Please, I don't feel pushed, this stuff is fun, I want to get back to
it. Can't wait to retire, so I can play all day.
I seem to recall a video of an aging Navy lady, she was teaching. She
ask what is a nanosecond, then held up 1 foot of wire and said, this is
a nanosecond. So, ya, 11 ft, 11ns, thanks for the memory jog.
I found the video, Admiral Grace Hopper, fun to watch.
http://www.youtube.com/watch?v=9eyFDBPk4Yw
http://www.youtube.com/watch?v=9eyFDBPk4Yw

It amazes me that I can see the the delay in a short piece of wire.
All of the sudden I see a value in my new 300 Mhz scope. Lower time base.

Let me setup the proposed experiment.
I'm measuring the delay in the shield of a coax. The R will be near zero
ohms so I'll probably change my sense resistor to a low value,
maybe one ohm, if I can find one. I should probably use a series 50 ohm
resistor to protect the 50 ohm in the signal generator.
Halt.
I'm rethinking that, I already have a 47.5 ohm sense resistor, so I
think I'm all set.
Won't there me some additional delay caused by the inductance of the
wire?
What is the inductance of a ft of wire.
Found this calculator.
> http://www.consultrsr.com/resources/eis/induct5.htm
I picked 0.5 cm for the dia. of coax shield. (?) I'm at work can't
measure, I don't know how a braided shield compares to a solid wire.
The calculator gives me 3.2uH for 11 ft of wire. Please check that for
me, seems high, but it is a weak, seems
Anyway, my first guess is I have a delay caused be length and a delay
caused by inductance. We will see.


Mike

 

[Fred Abse]

On Thu, 30 Jan 2014 19:03:41 -0800, Jeff Liebermann wrote:

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

alt.binaries.schematics.electronic

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[Fred Abse]

On Thu, 30 Jan 2014 16:45:04 -0600, amdx wrote:

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.

They don't look stripped around the probes.

I use tinned copper wire for such things.

--
"Design is the reverse of analysis"
(R.D. Middlebrook)

 

[Sal M. O'Nella]

"amdx" <nojunk@knology.net> wrote in message
news:lcgk6o$fip$1@dont-email.me...

It amazes me that I can see the the delay in a short piece of wire.
All of the sudden I see a value in my new 300 Mhz scope. Lower time base.

OFF TOPIC, SLIGHTLY:

With a wideband scope, you see many interesting things, including some that
might surprise you. Years ago, while looking at some short pulses (to
evaluate the response of a new amplifier), I saw unexpected "steps" in the
traces. I was using BNC T-connectors and my test setup had accidentally
duplicated a TDR function. The impedance change reflections were plainly
evident in a few feet of 50-ohm coax. (I've since seen plans for a
home-brew TDR similar to my accident.

I enjoy amazement, too.

"Sal"
(KD6VKW)

 

[John S]

On 1/31/2014 10:49 AM, amdx wrote:

On 1/31/2014 8:44 AM, John S wrote:
On 1/31/2014 7:21 AM, amdx wrote:
On 1/31/2014 6:49 AM, John S wrote:
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.

Yes that's what I did, problem follows the probes. I'm not surprised,
I have done a major repair to the metal housing that was broke in two
pieces. I seem to have ruined a solder tip soldering the metal the
housing is made off. The probes are at least 30 years old. I didn't
receive my new probes yesterday (as told) maybe today.

Okay. Use one probe to measure both amplitudes. Use both probes to
measure the phase (at zero-crossing only) while ignoring the amplitudes.

Otherwise, use your new (calibrated by you and verified by you) probes.


* 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.

I'll have to check that, an see if my "setup" verifies that.

This
leaves us in an even worse situation to explain high R and low L.

Ya, hmm.
I did find a data sheet for 3B7 but the loss graph only goes to 500kHz.
I'll take the book with me to work and see how the losses of this
material compare to others. Don't know if it is high loss or low loss.

I would not expect 3B7 to be of significant inductance at your frequency
of interest. It might be instructional to insert the coax into a piece
of conduit of the same length and measure it.


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

I will be busy all weekend, working for a living, I hope I can try
something sooner, but it might be next Tuesday.

I understand. I don't mean to push you.

John S

Please, I don't feel pushed, this stuff is fun, I want to get back to
it. Can't wait to retire, so I can play all day.
I seem to recall a video of an aging Navy lady, she was teaching. She
ask what is a nanosecond, then held up 1 foot of wire and said, this is
a nanosecond. So, ya, 11 ft, 11ns, thanks for the memory jog.
I found the video, Admiral Grace Hopper, fun to watch.
http://www.youtube.com/watch?v=9eyFDBPk4Yw
http://www.youtube.com/watch?v=9eyFDBPk4Yw

I saw a complete program on PBS about her. It was fascinating.

It amazes me that I can see the the delay in a short piece of wire.
All of the sudden I see a value in my new 300 Mhz scope. Lower time base.

Let me setup the proposed experiment.
I'm measuring the delay in the shield of a coax. The R will be near zero
ohms so I'll probably change my sense resistor to a low value,
maybe one ohm, if I can find one. I should probably use a series 50 ohm
resistor to protect the 50 ohm in the signal generator.
Halt.
I'm rethinking that, I already have a 47.5 ohm sense resistor, so I
think I'm all set.
Won't there me some additional delay caused by the inductance of the
wire?
What is the inductance of a ft of wire.
Found this calculator.
http://www.consultrsr.com/resources/eis/induct5.htm
I picked 0.5 cm for the dia. of coax shield. (?) I'm at work can't
measure, I don't know how a braided shield compares to a solid wire.
The calculator gives me 3.2uH for 11 ft of wire. Please check that for
me, seems high, but it is a weak, seems

I use 1nH/mm as a rule-of-thumb for a straight wire. For an 11-foot
straight wire, that would give about 3.3uH. But, remember that your wire
has additional inductance in the coiled portions.

Anyway, my first guess is I have a delay caused be length and a delay
caused by inductance. We will see.


Mike

 

[John S]

On 1/31/2014 3:32 PM, Sal M. O'Nella wrote:

"amdx" <nojunk@knology.net> wrote in message
news:lcgk6o$fip$1@dont-email.me...


It amazes me that I can see the the delay in a short piece of wire.
All of the sudden I see a value in my new 300 Mhz scope. Lower time base.

OFF TOPIC, SLIGHTLY:

With a wideband scope, you see many interesting things, including some
that might surprise you. Years ago, while looking at some short pulses
(to evaluate the response of a new amplifier), I saw unexpected "steps"
in the traces. I was using BNC T-connectors and my test setup had
accidentally duplicated a TDR function. The impedance change
reflections were plainly evident in a few feet of 50-ohm coax. (I've
since seen plans for a home-brew TDR similar to my accident.

I enjoy amazement, too.

"Sal"
(KD6VKW)

Right you are, Sal. I once used a 200MHz scope and a pulse generator to
measure the approximate length of a reel of coax. Handy stuff to know.

John S
KD5YI

 

[Ralph Mowery]

"amdx" <nojunk@knology.net> wrote in message
news:lcgk6o$fip$1@dont-email.me...

I seem to recall a video of an aging Navy lady, she was teaching. She ask
what is a nanosecond, then held up 1 foot of wire and said, this is a
nanosecond. So, ya, 11 ft, 11ns, thanks for the memory jog.
I found the video, Admiral Grace Hopper, fun to watch.
http://www.youtube.com/watch?v=9eyFDBPk4Yw
http://www.youtube.com/watch?v=9eyFDBPk4Yw

About 20 years ago there was a TV show on the PBS called the Computer
Chronicals. She was often on that program. She was given credit for the
terms bugs in the computer and debugging. Came from a moth in one of the
old relay type computers around the WW2 time.

She also has a navy ship named after, one of only 2 US navy ships named
after a woman.



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