Time-domain reflectometry or TDR is the ability to measure the distance to an electrical line fault based on reflections.
TDR analysis begins with the propagation of an 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 the case of a wire fault, there are reflections, whose delay depends on the propagation speed in the wires and the distance they traveled.
Sital’s off-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.
Sital’s Passive TDR (pTDR) technology can estimate the distance to the wire fault without transmitting any signal to the bus!
pTDR derives the required information from the ongoing 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 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 it is called passive).
pTDR is being used to detect and locate wire faults such as disconnection and shorts.
Being able to run on live wires enables this technology to accurately detect and locate intermittent faults.