Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [tdr]

34 questions
19
votes
8 answers

Electricity only flows in a complete circuit, so how does TDR (time domain reflectometery) work?

In high school we were all taught that electricity only flows in a loop. But it seems that one can send a "pulse" down an open conductor. This is used in a time-domain reflectometer. How is this possible? How can you send electricity down an open…
Jason
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2 answers

Time domain reflectometry and resolution

Regarding the temporal (and consequently spatial) resolution of a TDR system, I've read from different sources that the maximum resolution achievable is half of the rising time of the input step response, which is usually in the ns range. How is…
Anice41
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4
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1 answer

Time domain reflectometry (TDR), pulse shape

Considering this coax cable open end reflection. What are the correct explanations for the flatter rise time, the rounding of the first reflection, and the much smaller what I assume to be secondary reflection? EDIT: Cable: ~100m 50ohm…
bretddog
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4
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3 answers

Is it possible to measure TDR without a specialized device?

I've seen dedicated devices for measuring TDR and even layer 2&3 network switches with the TDR capability. My question is what would prevent a standard home router from being programmed to measure the same metrics? -Being on the 3rd OSI layer…
Landon Tholen
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4
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1 answer

What level of a square wave signal should be safe for TV receivers?

I am experimenting a bit with TDR (time domain reflectometry) and for it I am generating a square wave with up to 10kHz and a rise time of about 1-2ns. Now I would like to put that thing to use and see if I can figure out more about some cable tv…
PlasmaHH
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3
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4 answers

Determining conductance / capacitance and inductance per unit length

How do you determine conductance / capacitance and inductance per unit for a cable experimentally? Is there a way to determine them with only a oscilloscope and a pulse generator?
Yoomo
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3
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1 answer

frequency and type of pulse for time domain reflectometer (TDR)

I would like to apply the time domain reflectometry method in an fpga. However, I could not find information about the frequency and type of pulse used by reflectometer. Can anyone give me a guide?
Erile
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1 answer

How can I use the TDR result to evaluate the effect of impedance discontinuity?

Only the left half is relevant. Like mentioned before,I want to check out if reflection is one of the reason that deteriorates the signal integrity of high-speed signal.One way that has been come up is to reexamine the impedance of PCB traces(in…
Xiao Xiang
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2
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2 answers

High-Speed electronics - Reflections in T-intersection

I'm currently attending a course on "experimental problem solving" and we just started talking about TDR (time domain reflectometry). I do understand that reflections occur whenever there is a change of impedance, and that you can terminate them by…
Estrozix
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2
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1 answer

Time domain reflectometry (TDR), initial pulse slope

A ~100kHz square wave through a 100m open end coax (RG-58) produces a slightly sloped shoulder during the time from initial pulse until reflected pulse (A-B), and from initial pulse drops until reflected pulse ends (C-D). What are the correct…
bretddog
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0 answers

Time domain reflectometer (TDR) to check health of voice coil

I have some large voice coils in which the insulation is failing. We first notice this when the amplifier trips off on over current (short to ground.) I'm wondering if before the catastrophic fault that there are small shorts between coils that…
gamma_sponge
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1 answer

Could a time-domain reflectometer, with no access to earth-ground, indicate if a long-wire is attached to the end of a long steel beam?

Without using any other wiring, optics, RF, sound, or vibration, I need to know if a 100 meter length of electrical wire is attached to the end of a 50 meter long steel beam. I only have physical access to one end of the beam (not the end…
John Hassell
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0 answers

time domain reflectometry pulse

Today I investigated a cable which is around 900m long. I used a TDR that injects a needle pulse into the system with a width of around 40ns. The needle pulse had an amplitude of around 2V. A reflection never came back. I wonder why there wasn't a…
Yoomo
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1
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0 answers

Detecting an electrical connection without a complete circuit

Wired Fencing In a regular (wired) fencing system (for sabre and foil,) contact is determined simply by applying a current to the weapon through a wire and forming a circuit between a conductive jacket called a lame which is in turn connected to a…
mhh
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1 answer

using sig generator and scope as TDR for troubleshooting ethernet

I had some problems with a new run of cat5e. I have already established it's definitely a damaged cable using a cheap network continuity tester and double checking my wiring and crimps. I saw on YouTube there are people using a signal gen and scope…
Ageis
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