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Delay in 3 meters of wire

Started by amdx February 4, 2014
Hi Guys,
  I have question about transit time in a wire and phase shift caused by 
inductance.
I'm going to use 3 meters of wire and 300,000,000m/s  (discuss speed later)

300,000,000m/3m =10 nanoseconds,
What travels?
Will I measure both current and voltage as having a 10 ns delay at the 
other end of the wire?

Now, I wind the 3 meters of wire as a solenoid coil and I have a 30 uh 
coil.
Now I will have a 90* phase shift between the current and voltage.

  (I think I may have stumbled on my answer, but, let me continue.)

  How does the 10ns add to the 90* phase shift.

  Ok, to try and answer my own question:

The current and voltage both have a delay from one end of the wire to 
the other.
If I'm looking at the voltage across and current through the inductor, 
the 10ns
delay will not be seen. Both voltage and current will be delayed the 
same amount.
  However the current will have a 90* phase shift compared to the voltage.
  And both voltage and current will have delay of 10ns.

  Did I get it right?
Can anyone help?
                        Thanks, Mikek

Discuss speed later,
I didn't get to where I needed to discuss it.
But, I understand RG58/U has .66 velocity factor,
so 300,000,000m/s would reduce to 198,000,000m/s.
Ladderline .91 velocity factor.

amdx wrote:


> > The current and voltage both have a delay from one end of the wire to > the other. > If I'm looking at the voltage across and current through the inductor, > the 10ns > delay will not be seen. Both voltage and current will be delayed the > same amount. > However the current will have a 90* phase shift compared to the voltage. > And both voltage and current will have delay of 10ns.
Yeesh, this gets MESSY! The delay from one end of a wire to the other is kind of a transmission line problem, and you need to know the impedance of the transmission line to know the propagation velocity. Just wire in open air is uncontrolled impedance, so I have no idea how that works. Now, when you wrap it into a coil, part of the coil acts as the ground plane for every segment of conductor that acts as a transmission line. Messier, still! Jon
On 2/4/2014 8:57 PM, Jon Elson wrote:
> amdx wrote: > > >> >> The current and voltage both have a delay from one end of the wire to >> the other. >> If I'm looking at the voltage across and current through the inductor, >> the 10ns >> delay will not be seen. Both voltage and current will be delayed the >> same amount. >> However the current will have a 90* phase shift compared to the voltage. >> And both voltage and current will have delay of 10ns. > Yeesh, this gets MESSY! The delay from one end of a wire to the > other is kind of a transmission line problem, and you need to know the > impedance of the transmission line to know the propagation velocity. > Just wire in open air is uncontrolled impedance, so I have no idea > how that works. Now, when you wrap it into a coil, part of the coil > acts as the ground plane for every segment of conductor that acts > as a transmission line. Messier, still! > > Jon >
No need to get messy, just a yes or no. :-) I don't want numbers, just the just the explanation of how phase shift caused by inductance and time delay are related when measuring the inductance of a long wire. ( I think it can be ignored but... ) Ok, let me try again. If I have a series R L circuit and it has a 62 degree phase shift. Does the transit time have anything to add to or subtract from the the phase shift? Or another try. Say a straight wire has 15nh per inch and 1800nH per 10ft. If I make a series R L circuit with 10ft of wire and a 50 ohm resistor, Will this have a different phase shift than a series circuit with physically small 1800nH inductor and a 50 ohm resistor? Mikek
Jon Elson wrote:
> amdx wrote: > > >> >> The current and voltage both have a delay from one end of the wire to >> the other. >> If I'm looking at the voltage across and current through the inductor, >> the 10ns >> delay will not be seen. Both voltage and current will be delayed the >> same amount. >> However the current will have a 90* phase shift compared to the voltage. >> And both voltage and current will have delay of 10ns. > Yeesh, this gets MESSY! The delay from one end of a wire to the > other is kind of a transmission line problem, and you need to know the > impedance of the transmission line to know the propagation velocity. > Just wire in open air is uncontrolled impedance, so I have no idea > how that works. Now, when you wrap it into a coil, part of the coil > acts as the ground plane for every segment of conductor that acts > as a transmission line. Messier, still! > > Jon
"Just wire in open air" has a reasonably controlled impedance; if you do not believe me, just look at what the Bell System did to pairs of wire for the pone system, as well as the (then) counter-intuitive practice of INDUCTIVE loading.
On Tue, 04 Feb 2014 20:39:48 -0600, amdx <nojunk@knology.net> wrote:

>Hi Guys, > I have question about transit time in a wire and phase shift caused by >inductance. >I'm going to use 3 meters of wire and 300,000,000m/s (discuss speed later) > >300,000,000m/3m =10 nanoseconds, >What travels? >Will I measure both current and voltage as having a 10 ns delay at the >other end of the wire? > >Now, I wind the 3 meters of wire as a solenoid coil and I have a 30 uh >coil. >Now I will have a 90* phase shift between the current and voltage. > > (I think I may have stumbled on my answer, but, let me continue.) > > How does the 10ns add to the 90* phase shift. > > Ok, to try and answer my own question: > >The current and voltage both have a delay from one end of the wire to >the other. >If I'm looking at the voltage across and current through the inductor, >the 10ns >delay will not be seen. Both voltage and current will be delayed the >same amount. > However the current will have a 90* phase shift compared to the voltage. > And both voltage and current will have delay of 10ns. > > Did I get it right? >Can anyone help? > Thanks, Mikek > >Discuss speed later, >I didn't get to where I needed to discuss it. >But, I understand RG58/U has .66 velocity factor, >so 300,000,000m/s would reduce to 198,000,000m/s. >Ladderline .91 velocity factor.
I think phase shift is a property of an established sinusoidal signal (at some specified, established frequency, too), while propagation delay is a transient phenomenon, so they're not really comparable. -- John
El 05-02-14 4:24, amdx escribi&#2013265923;:
> On 2/4/2014 8:57 PM, Jon Elson wrote: >> amdx wrote: >> >> >>> >>> The current and voltage both have a delay from one end of the wire to >>> the other. >>> If I'm looking at the voltage across and current through the inductor, >>> the 10ns >>> delay will not be seen. Both voltage and current will be delayed the >>> same amount. >>> However the current will have a 90* phase shift compared to the >>> voltage. >>> And both voltage and current will have delay of 10ns. >> Yeesh, this gets MESSY! The delay from one end of a wire to the >> other is kind of a transmission line problem, and you need to know the >> impedance of the transmission line to know the propagation velocity. >> Just wire in open air is uncontrolled impedance, so I have no idea >> how that works. Now, when you wrap it into a coil, part of the coil >> acts as the ground plane for every segment of conductor that acts >> as a transmission line. Messier, still! >> >> Jon >> > > No need to get messy, just a yes or no. :-) > > I don't want numbers, just the just the explanation of how phase shift > caused by inductance and time delay are related when measuring the > inductance of a long wire. ( I think it can be ignored but... ) > > Ok, let me try again. > If I have a series R L circuit and it has a 62 degree phase shift. > Does the transit time have anything to add to or subtract from the > the phase shift? > > Or another try. > Say a straight wire has 15nh per inch and 1800nH per 10ft. > If I make a series R L circuit with 10ft of wire and a 50 ohm resistor, > Will this have a different phase shift than a series circuit with > physically small 1800nH inductor and a 50 ohm resistor? > > Mikek
Whether or not physical length has influence, depends on the frequency. Rough guideline: when the physical length of the wire is less then 0.1*lambda for the highest frequency, you can ignore transmission line effects. So you can calculate with lumped inductance and lumped capacitance. For your long wire, calculate the capacitance and inductance and you can convert that to (for example) a CLC network for simulation. you need to take the return path into account as this affects the inductance and capacitance. So the 15 nH/inch you mentioned may not apply. -- Wim PA3DJS www.tetech.nl Please remove abc first in case of PM
On 2/5/2014 12:47 AM, quiasmox@yahoo.com wrote:
> On Tue, 04 Feb 2014 20:39:48 -0600, amdx <nojunk@knology.net> wrote: > >> Hi Guys, >> I have question about transit time in a wire and phase shift caused by >> inductance. >> I'm going to use 3 meters of wire and 300,000,000m/s (discuss speed later) >> >> 300,000,000m/3m =10 nanoseconds, >> What travels? >> Will I measure both current and voltage as having a 10 ns delay at the >> other end of the wire? >> >> Now, I wind the 3 meters of wire as a solenoid coil and I have a 30 uh >> coil. >> Now I will have a 90* phase shift between the current and voltage. >> >> (I think I may have stumbled on my answer, but, let me continue.) >> >> How does the 10ns add to the 90* phase shift. >> >> Ok, to try and answer my own question: >> >> The current and voltage both have a delay from one end of the wire to >> the other. >> If I'm looking at the voltage across and current through the inductor, >> the 10ns >> delay will not be seen. Both voltage and current will be delayed the >> same amount. >> However the current will have a 90* phase shift compared to the voltage. >> And both voltage and current will have delay of 10ns. >> >> Did I get it right? >> Can anyone help? >> Thanks, Mikek >> >> Discuss speed later, >> I didn't get to where I needed to discuss it. >> But, I understand RG58/U has .66 velocity factor, >> so 300,000,000m/s would reduce to 198,000,000m/s. >> Ladderline .91 velocity factor. > > I think phase shift is a property of an established sinusoidal signal > (at some specified, established frequency, too), while propagation > delay is a transient phenomenon, so they're not really comparable. >
In the end, I think this transit time is a wash in calculations. But I can't seem to get a solid feel for it. I keep going back and forth. This goes back to a couple of threads on sci.electronics.basics, Question on R L math" and "More math for "SETUP" I don't care to rehash those now, but I'll give an explanation of the "setup" and to show why I ask the question. My drive voltage is a sinewave. I'm looking at the Voltage at the INPUT (beginning) to an inductor. I'm also looking at the current at the OUTPUT (end) of the inductor. (I'm looking at current by monitoring the voltage across a sense resistor) To repeat, I'm looking at the beginning of the inductor (wire) on channel one and the end of the inductor (wire) with channel two. Is there a delay for transit time along with a phase shift caused by the inductance? I don't think there is, because both V and I have the same transit delay in the measurement. But... Mikek
On Wed, 05 Feb 2014 08:11:09 -0700, amdx <nojunk@knology.net> wrote:

>> ...snip... > In the end, I think this transit time is a wash in calculations. > But I can't seem to get a solid feel for it. I keep going back and forth. > > This goes back to a couple of threads on sci.electronics.basics, > Question on R L math" and "More math for "SETUP" > I don't care to rehash those now, but I'll give an explanation of the > "setup" and to show why I ask the question. > > My drive voltage is a sinewave. > I'm looking at the Voltage at the INPUT (beginning) to an inductor. > I'm also looking at the current at the OUTPUT (end) of the inductor. > (I'm looking at current by monitoring the voltage across a sense > resistor) > To repeat, I'm looking at the beginning of the inductor (wire) on > channel one and the end of the inductor (wire) with channel two. > Is there a delay for transit time along with a phase shift caused by > the inductance? > > I don't think there is, because both V and I have the same transit delay > in the measurement. But... > Mikek > >
WOW! you have a way of asking the most mind boggling 'simple' questions. Bet like most people, I've spent a lifetime 'ignoring' such simple questions, rounding off the answers, so to speak, so is not an easy task to answer your question. In defense, my justification for not thinking about what you just asked is this: the delay of the transmission line can be EXACTLY duplicated with a series of distributed very tiny inductors with capacitance to GND. Therefore as the overall inductance increases when you bend the whole wire into a loop it becomes IMPOSSIBLE to tell exactly where the contribution to the inductance is coming from. You can't tell if it comes from the self-inductance and coupling because you bent the wire into a loop, or if it comes from the 'length' of the wire. It just is. And, that original straight wire inductance, being small contribution, just gets scooped into the overall inductance and buried in the error budget. From memory working with HP's Network Analyzer, the length of a single turn inductor is the max you'll ever get [air core] you can loop it 2, or 3 times, but the diameter gets smaller so you're left with approximately the SAME inductance no matter how you bend up your wire. Anybody confirm that memory? Or, verify using femm? To show you how much I've been ignoring simple questions, I'm not even going to get into the 'coupling' to free space and launching energy, which obfuscates everything even more.
On Tue, 04 Feb 2014 20:39:48 -0600, amdx wrote:

> Hi Guys, > I have question about transit time in a wire and phase shift caused by > inductance. > I'm going to use 3 meters of wire and 300,000,000m/s (discuss speed > later) > > 300,000,000m/3m =10 nanoseconds, > What travels? > Will I measure both current and voltage as having a 10 ns delay at the > other end of the wire?
Measure how? Your single wire in free space is going to act like a lot of things, but the one thing it won't act like is a clean transmission line. The most likely thing it'll act like is an antenna, which means that it'll radiate away the energy of the sharp edges of your pulses, or delay it in hard to predict ways.
> Now, I wind the 3 meters of wire as a solenoid coil and I have a 30 uh > coil. > Now I will have a 90* phase shift between the current and voltage. > > (I think I may have stumbled on my answer, but, let me continue.) > > How does the 10ns add to the 90* phase shift.
Again, you're so far from a transmission line that the answers will be nearly meaningless. Are you trying to do something real, or just pondering? -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
On 2/5/2014 10:08 AM, RobertMacy wrote:
> On Wed, 05 Feb 2014 08:11:09 -0700, amdx <nojunk@knology.net> wrote: > >>> ...snip... >> In the end, I think this transit time is a wash in calculations. >> But I can't seem to get a solid feel for it. I keep going back and forth. >> >> This goes back to a couple of threads on sci.electronics.basics, >> Question on R L math" and "More math for "SETUP" >> I don't care to rehash those now, but I'll give an explanation of the >> "setup" and to show why I ask the question. >> >> My drive voltage is a sinewave. >> I'm looking at the Voltage at the INPUT (beginning) to an inductor. >> I'm also looking at the current at the OUTPUT (end) of the inductor. >> (I'm looking at current by monitoring the voltage across a sense >> resistor) >> To repeat, I'm looking at the beginning of the inductor (wire) on >> channel one and the end of the inductor (wire) with channel two. >> Is there a delay for transit time along with a phase shift caused by >> the inductance? >> >> I don't think there is, because both V and I have the same transit delay >> in the measurement. But... >> Mikek >> >> > > > WOW! you have a way of asking the most mind boggling 'simple' questions. > Bet like most people, I've spent a lifetime 'ignoring' such simple > questions, rounding off the answers, so to speak, so is not an easy task > to answer your question.
I think that means you understood the question. However useless the question may be. Again, in the end I think it washes out. But I can't get my head around how.
> In defense, my justification for not thinking about what you just asked > is this: the delay of the transmission line can be EXACTLY duplicated > with a series of distributed very tiny inductors with capacitance to > GND. Therefore as the overall inductance increases when you bend the > whole wire into a loop it becomes IMPOSSIBLE to tell exactly where the > contribution to the inductance is coming from. You can't tell if it > comes from the self-inductance and coupling because you bent the wire > into a loop, or if it comes from the 'length' of the wire. It just is. > And, that original straight wire inductance, being small contribution, > just gets scooped into the overall inductance and buried in the error > budget. > > From memory working with HP's Network Analyzer, the length of a single > turn inductor is the max you'll ever get [air core] you can loop it 2, > or 3 times, but the diameter gets smaller so you're left with > approximately the SAME inductance no matter how you bend up your wire. > Anybody confirm that memory? Or, verify using femm? >
Oh, my first thought, that's not right. I can wind a high Q, 240 uh inductor with 55 ft of #18 wire, (turns spaced 1 wire width apart). A straight wire, 55ft long of #18 wire has 35uh of inductance.
> To show you how much I've been ignoring simple questions, I'm not even > going to get into the 'coupling' to free space and launching energy, > which obfuscates everything even more.
Mikek