How does a time domain reflectometer TDR measure the distance to a reflection from a fault or the end of a cable?

A TDR works like radar. A fast rise time pulse is injected into the cable system at one end (near end). As the pulse travels down the cable, any change in the characteristic impedance (impedance discontinuities) will cause some of the incident signal to be reflected back towards the source.

What is the function of a time domain reflectometer TDR?

Time domain reflectometers (TDR) are test devices that generate an energy pulse or step on the cable to determine the location and magnitude of cable faults, breaks, splices, terminations, or other events along the length of a conductive cable.

What are the advantages of TDR over regular Ohmmeters when troubleshooting cables?

The TDR’s advantage would be that it does not require an above ground reference wire, but from a practical point of view, a TDR cannot accurately measure the amount of remaining neutral.

How does a TDR cable tester work?


The TDR sends a pulse of energy down the cable under test; when the pulse encounters the end of the cable or any cable fault, a portion of the pulse energy is reflected. The elapsed time of the reflected pulse is an indication of the distance to the fault.

How does a time domain reflectometer TDR work quizlet?

A time domain reflectometer sends a signal and analyzes the return signal’s change in amplitude to determine where cable imperfections may exist.

How do you measure TDR?

Quote from the video:
Quote from Youtube video: For the other thing that we use this tdr for is to check the cables. And our printed circuit board traces. Including the printed circuit board coupons. So i'm using the same generator 32 per second

How is TDR impedance measured?

TDR feeds a pulse onto the PCB trace/transmission line on a test coupon. Then it measures the characteristic impedance by analyzing the changes in the amplitude of the reflected waveform. Note that TDR will only observe the reflections if the injected pulse experiences any discontinuity in its path.

What is a TDR oscilloscope?

A time-domain reflectometer (TDR) is an electronic instrument used to determine the characteristics of electrical lines by observing reflected waveforms.

What is TDR test in Cisco switch?

The Time Domain Reflectometer (TDR) feature allows you to determine if a cable is OPEN or SHORT when it is at fault. TDR feature is supported on the following modules: Note. Running the TDR Test.

How do I read TDR cable diagnosis?

Quote from the video:
Quote from Youtube video: You show cable Diagnostics TDR to read the test results. So I've waited a few seconds now I'm gonna go ahead and run the command. Show cable Diagnostics TDR interface gig 101.

How do I find the cable length on a Cisco switch?

Checking the Cable Status Using the TDR

  1. You can check the status of copper cables using the time domain reflectometer (TDR). …
  2. % Interface Gi0/1 is administratively down.
  3. % Use ‘no shutdown’ to enable interface before TDR test start.
  4. Note: TDR can test cables up to a maximum length of 115 meters.

How do I check the fiber ports on a Cisco switch?

Log in to the switch console to run the privileged EXEC mode of the Cisco switch, use the fiber-ports-optical-transceiver command. The Output Power (mWatt) field in the command output indicates the received power of the optical module, and the Input Power (mWatt) field indicates the transmit power.

How do I know if my Cisco port is copper or fiber?

There are a few ways to determine this:

  1. sh module – This will tell what line cards are available. Some line cards are purely optical. …
  2. sh inventory – This command will tell what different type of SFP/SFP+, GBIC, X2/XENPAC, etc are installed.
  3. sh interface – This will say if the port is copper or not. 0 Helpful.

What is a good fiber light reading?

Multimode fiber is commonly used to transmit light for shorter distances and moderate data rates usually at 850 nm, and less commonly at 1300 nm .

Connector & other device loss discussion.

Component Loss
1550 nm 0.17 -0.22 dB/km
Multimode 850 nm 2.5 – 3.0 dB/km
1310 nm 0.7 – 0.8 dB/km
Connectors 0.1 – 0.75 dB