SPRINGBOK Cable Measurement Technology – TDR Cable Location

With the Tracker Store function, the instrument saves the full waveform at the touch of a button, regardless of what is on screen; the TRACKER PRO cycles through all of its pulse widths in the process. Stored waveforms can be recalled on the instrument or downloaded – both models have USB and Bluetooth 4.0. In the TrackerView software for Windows and the app for iOS and Android, waveforms can be named and annotated, VOP, gain and range changed, pulse widths stepped through, cursors moved, distances and dBRL measured, and waveforms printed together with comments.

Always with the shortest pulse width available, because the fault may be only a short distance away. Use the range (zoom) and gain controls to search the trace; if the fault is not found, switch to the next larger pulse width and test again until it is located. Wider pulses transmit more energy and therefore travel further down the cable, while a higher vertical gain makes smaller reflections visible.

The VOP value depends on the cable's dielectric and changes with temperature, age and humidity; even new cable can vary by as much as ±3%. The cable manufacturer can provide the value, or it can be determined on a cable of known length:

1. Measure a cable of known length – the longer the cable, the more accurate the result.
2. Place the cursors on the output pulse and on the reflection from the cable end.
3. Adjust the VOP until the distance between the cursors equals the known length.

To pinpoint a fault accurately, it is advisable to measure from both cable ends to the fault: if the sum of the two distances is greater than the cable length, reduce the VOP; if it is smaller, increase it.

Dust is removed from the housing and connectors with a lint-free cloth; for damp cleaning, use only a slightly damp cloth with the instrument switched off and the charger unplugged. Harsh chemicals and abrasive cleaners can damage the front panel overlay. The instrument and accessories should be inspected regularly for damage, wear and missing parts – after every use if operated in harsh, dusty or wet environments; test leads with damaged insulation or bent or broken clips should be replaced. The instrument contains no user-serviceable parts.

AUTO SEARCH moves cursor 3 to the largest impedance mismatch on the trace and zooms in on it. If the far end of the cable is disconnected from the cable plant, the largest reflection is the cable end, so the cursor moves to the end. If the cable is still connected, the cursor moves to the largest mismatch along the line.

The TRACKER STD (manufacturer's designation “Tracker”) and the TRACKER PRO differ mainly in range, pulse widths and memory:

Both share a USB connection, Bluetooth 4.0 and a distance accuracy of 0.44 ft at 99% VOP down to 0.18 ft at 40% VOP, among other things.

The TRACKER PRO is a metallic time-domain reflectometer: it tests all types of paired metallic cables – twisted pair as well as coaxial cable – for opens, shorts and impedance mismatches. The cable is connected to the BNC socket on the front panel; for coaxial cable with an F connector, a BNC-to-F adapter is used.

The TRACKER PRO sends pulses down the cable; at impedance discontinuities some or all of the energy is reflected back and displayed as a waveform with a distance readout. The following applies:

• Open: the reflection has the same polarity as the output pulse and points upwards.
• Short: the reflection has the opposite polarity and points downwards.
• Inductive faults and points of higher impedance show upwards, capacitive faults and points of lower impedance downwards.

A cable with constant impedance that is properly terminated absorbs all of the energy and produces no reflection.