Time-domain reflectometer (TDR)

Data records

• Handheld reflectometers are designed for metallic cable pairs of all kinds, with selectable output impedances to match the cable under test and with built-in blocking filters and fused test leads that guard the instrument against a cable that turns out to be energized. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.time-domain-reflectometer.applications
• The reflection trace is drawn against distance on a graphical display; dual cursors give the distance between two selected points, and a trace hold function keeps a stored trace on screen for comparison with another cable or another condition. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.time-domain-reflectometer.display-and-cursors
• On a mixed cable route the velocity of propagation differs between sections, so the fault position cannot be computed exactly from one end; measuring from both ends gives two positions and the fault generally lies about midway between them, after which careful pinpointing is recommended. Source: BAUR application page, web page edition. Verified 2026-10-27. Record instr.time-domain-reflectometer.mixed-routes
• In power cable fault location the reflectometer is the prelocation instrument: it locates low-resistance faults, cable ends and joints directly with its own pulse, and it records the traces for the high-voltage prelocation methods when it operates together with a surge wave generator. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.time-domain-reflectometer.prelocation-role
• A time-domain reflectometer injects a low-voltage pulse at one end of a cable; wherever the impedance between the conductors changes, part of the pulse is reflected back to the instrument, and the distance to that point is derived from the time between transmission of the pulse and registration of the echo. Source: BAUR application page, web page edition. Verified 2026-10-27. Record instr.time-domain-reflectometer.principle
• An open cable end or a break returns a positive reflection, a short circuit is also visible in the reflection image, and a joint or a transition between cable sections appears as a horizontal S-shaped feature; a positive reflection arriving before the cable end indicates a break. Source: BAUR application page, web page edition. Verified 2026-10-27. Record instr.time-domain-reflectometer.reflection-signatures
• The instrument class is written Time-domain reflectometer (TDR). Value: Time-domain reflectometer (TDR). Source: Electrical Testing Reference editorial taxonomy, 2026-10 edition. Verified 2026-10-27. Record instr.time-domain-reflectometer.title
• A two-channel reflectometer measures two phases at the same time or performs a differential measurement between them, so that the affected phase is distinguished by genuine differences between the traces rather than by manual comparison of separate measurements. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.time-domain-reflectometer.two-channel-comparison
• The distance scale depends on the velocity factor (velocity of propagation) set on the instrument for the cable under test, and handheld instruments allow the factor to be set over a wide range so that any cable construction can be measured; the maximum range likewise depends on the factor selected and the cable type. Source: Megger product page, web page edition. Verified 2026-10-27. Record instr.time-domain-reflectometer.velocity-factor