Autotest 3
Autotest Results for Twisted Pair Cable
Propagation Delay and Delay Skew
Propagation delays are the times taken in nanoseconds for a test pulse to travel the length of each cable pair.
Delay skews are the differences in propagation delays between the shortest delay, which is displayed as 0 ns, and the delays of the other cable pairs.
The propagation delay and delay skew results show a limit if the test is required by the selected test standard. If the test is not required, the results always show PASS.
Characteristic Impedance
The characteristic impedance test determines the approximate characteristic impedance of each cable pair.
Note
Impedance measurements require a cable at least 5m (16 ft) long.
Cables shorter than this length will always pass the impedance test.
A PASS result means that the measured impedance is within the specified limit for the selected test standard. A FAIL result means that the measured impedance exceeds the specified limit, or an impedance anomaly is detected.
A Warning result means that the measured impedance exceeds test limits, but the characteristic impedance test is not required by the selected test standard. The warning result causes a warning to appear as the test summary result in printed reports.
If an impedance anomaly is detected on a cable pair, the display shows the distance to the anomaly (in meters or feet) and the result is displayed as FAIL. The test tool reports an anomaly if 15% or more of the test signal is reflected. If more than one anomaly is detected on a cable pair, the distance to the largest anomaly is displayed. You can use the TDR test to plot the locations and sizes of impedance anomalies on the cable.
