How to Test PCB Traces with a TDR

 

Every printed circuit board hides a story in its copper pathways, and the ability to read that story accurately is crucial. At BitWise Laboratories, we specialize in helping engineers uncover the health of their PCBs using advanced diagnostic tools like Time Domain Reflectometry (TDR).

TDR works by sending a very fast electrical pulse into a trace and then analyzing the reflections that return. If the trace is continuous and properly matched to its intended impedance, the pulse travels smoothly with minimal distortion. However, any break, short, or impedance mismatch along the line will send part of the signal back, creating a reflection that reveals where the problem lies. This method is especially powerful because it not only detects faults but also pinpoints their exact location 

To test PCB traces with a TDR, the first step is connecting the probe or test lead to the trace under evaluation. A reference calibration is performed to account for cable length and connector influence. Once the system is zeroed, the trace is excited with a high-speed edge. The TDR screen will display a waveform that represents the electrical journey. A flat, steady line indicates a healthy trace, while spikes, drops, or irregularities highlight defects such as opens, shorts, or impedance discontinuities.

One major advantage of this approach is speed. Traditional continuity tests might show if a trace conducts, but they cannot reveal subtle issues like impedance mismatches that could cripple high-frequency performance. With TDR, engineers get a full electrical map in seconds, ensuring signal integrity and reliability.

At BitWise Laboratories, we recommend TDR testing for every high-speed PCB design project. By learning how to test PCB traces with a TDR, engineers safeguard performance, reduce costly rework, and deliver dependable products that meet today’s demanding standards.