I am very curious about the practical details of measuring impedance with a TDR. Never owned or used one, my only knowledge is based on what I have been able to read. I believe the reading has given me a high-level overview of how the instruments work, but I have not found much that help understands how to make the measurements successfully and how to understand the traps and limitations for various instruments.
A few of the questions:
From what I understand, TDR's make relative measurements so it should be able to deal with various common impedances of DUTS? Not just 50ohms......
Is it practical/common to directly measure traces on a PCB or only using test coupons printed adjacent to the PCB design?
With a single channel TDR, is it possible to measure a differential structure on a PCB?
What kind of fixtures, probes, calibration devices are common for TDR's configured for measuring PCB structures, connectors, FPC's, etc.
If anyone has some practical experience they are willing to share, or perhaps links to reading materials or videos that accomplish the same - it would be appreciated.