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What Does the Advanced Cable Tester v2 Measure Cables and How Accurate are the Measurements?
Rena Ayeras

Accurate measurements of USB type-C and HDMI cables

Photo from ID005645

Question from the Customer:

I have a new project that includes evaluating two types of cables: USB Type-C to USB Type-C and HDMI.  Before I get started, I have a few questions about the Advanced Cable Tester v2 (ACT v2):

  • When testing the signal integrity at 10Ghz level, which data pattern does it use for the test?
  • Regarding the resistance measurement, how accurate is the measured resistance value?
  • The signal integrity test displays the % number to show the level of opening the "Eye". What is this % value based on?
Response from Technical Support:

Thanks for your questions! The following sections provide the information that you requested. We also have a video to watch about using the ACT v2 with HDMI cables.

Measurement Patterns and Test Durations

When testing signal integrity, the Advanced Cable Tester v2 uses PRBS9 for the pattern, regardless of the bitrate.

The duration of the signal integrity test is about 2.5ms per channel. A very high number of pseudorandom binary sequence (PRBS) cycles are captured during that period.

Cable Measurements

Specific techniques are applied per cable type, as described in the following sections.

HDMI Measurements

When a cable is used with variable de-emphasis, such as HDMI, we search for the best de-emphasis value dynamically. This search can be disabled in the profile. The best one is used for qualification. When a cable is typically not used with variable de-emphasis (USB),  by default we use the de-emphasis value from the specification. The chosen de-emphasis value is provided in the test report.

Here is a video showing an example of using the ACT v2 for testing HDMI cables, as well as the test results.

USB Type-C Measurements

With USB Type-C cables, the measurement accuracy of individual power pins can be unpredictable. The resistance of a single contact on a Type-C connector can vary significantly, depending on each individual insertion event. In addition, contact wear and dirt can cause problems.

However, the resistance measurement is very accurate for the full end-to-end DCR values. This is because 4-wire measurement techniques are applied at the point where the connector interfaces to the module PCB.

Resistance and Eye Diagram Percentage Values

The eye percentage is relative to the full-scale received DC signal. The lowest frequency constitutes 100%, because that is what the receiver's automatic gain normalizes to. The highest frequencies have more loss through the cable, which are measured.

We hope this answers your questions. Additional resources that you may find helpful include the following:

If you want more information, feel free to contact us with your questions, or request a demo that applies to your application.