Passive TDR

What is Time-Domain-Reflectometry (TDR)?

Time-domain reflectometry or TDR is the ability to measure the distance to electrical line fault based on reflections.
TDR analysis begins with the propagation of energy impulse into the system and the subsequent observation of the energy reflected by the system.
When using TDR in a serial communication bus like a CAN bus, If the bus is intact, there are no reflections and all the energy turns to heat on the terminators.
In case of a wire fault, there are reflections, who’s delay depend on the propagation speed in the wires, and the distance they traveled.
Of-the-shelf TDR tool transmits a pulse to the line, and measures the time to its reflection to estimate the distance in nanoseconds (ns) to the fault location.


Understanding Passive Time-Domain-Reflectometry (pTDR)

Sital’s Passive TDR (pTDR) technology can estimate the distance to the wire fault without transmitting any signal to the bus!
pTDR derive the required information from the on-going communications on the line without disturbing the ongoing bus activity.
When there is a bus disconnection, the reflections (from the ongoing signals) distort the communication signals and change the their pulse width.
Measuring the distortion of a pulse width from its standard value provides the TDR information.
Passive TDR is the only TDR technique which does not send any signal to the bus (therefore called passive).
pTDR is being used to detect and locate wire faults such as disconnection and shorts.
Being able to run on live wires enable this technology to accurately detect and locate intermittent faults.

Sital’s pTDR technology is capable of detecting wiring problems such as disconnections, short-circuits, and others, in many cases even before the functionality of the system is hurt.

pTDR Added Value:
–  Capture first wire intermittent failure
–  Early detection of wires faults
–  Reduce “No-Trouble-Found” for wires failures
–  Distinguish wire Vs. module failures
–  Increase repair efficiency
–  Reduce false module replacement
–  Added diagnostics capabilities
–  Improve Customer Satisfaction


pTDR does not require any changes to the network, terminals or the transmitted data.

The pTDR technology is already in use by automotive manufacturers for detecting wiring faults on vehicles during manufacturing, maintenance and operation.