How Cable Testing Ensures Safety and Quality of Manufacturing

Testing cables is one of the most importance aspects of cable production. There are multiple features and components within a cable that need to work correctly and safely, and verifying these can easily be missed or disregarded if the proper quality control is not implemented by manufacturing. Performing a set of comprehensive tests that include checks for continuity, DCR and IR drop, E-Marker verification, and signal integrity is vital to ensure safety and quality. Fortunately, Total Phase offers the ability to confidently test each of these with the Advanced Cable Tester v2.

 Advanced Cable Tester and Test Panels

The Advanced Cable Tester v2 performs complete quality and safety checks on a variety of cable types.

Prevent Power Related Failures

Continuity Testing

Continuity testing analyzes the cable for any shorts or opens of various pins, including VBUS/GND, which can be very dangerous if not properly wired. It’s possible for there to be shorts of VBUS to data signals or VBUS/GND reversal, which can cause improper operation or overheating.  Continuity testing consists of applying a voltage at one end of the cable and measuring the incoming signal at the opposite end of the cable. The inputs are weakly pulled to the voltage rail, or supply voltage, to prevent false readings from a floating conductor. The Advanced Cable Tester v2 conducts the following tests to ensure proper configuration:

  1. VBUS to Ground Short
  2. CC/VCONN to Ground Short
  3. VBUS to CC/VCONN Short
  4. Shorts between all other pins
  5. Continuity of defined and present pins
  6. Mis-wires of defined and present pins

IR Drop/DCR Testing

IR Drop is important to test for the safe operation and reliability in cables. Cables supplying power will naturally experience IR Drop, which is essentially the calculation of voltage loss resulting from the resistance of metal wires to current flow. A higher voltage drop occurs when there is high resistance within a cable.  This can be due to multiple reasons, including the incorporation of loose or irregular circuitry. Without testing the IR Drop, consequences include unsafe delivery of voltage levels, which can cause the cable to operate unexpectedly or inefficiently, or may even cause fires due to the high resistance heating.

The IR Drop test performed by Advanced Cable Tester v2 confirms that each power pin, including VBUS or GND, is capable of carrying the required current, and for USB Type-C cables, each pin is measured individually and then the cable itself as a whole.

DCR, or direct current resistance, is also an important measure to prevent any failure in power delivery. The DCR is the electrical resistance of a conductor that is calculated based on temperature and the frequency of the voltage. Cable manufacturers must be aware of such outputs because a high resistance could mean that the cable may inadequately carry current end to end, and a higher heat of the conductor may cause short circuiting due to failure of insulation within the cable. A low resistance could mean that there is an excessive amount of inductive materials within the cable, such as copper, that could result in increased costs of the cable itself.

The Advanced Cable Tester v2 tests for DCR by applying a small current at one end of the cable and then measuring various parts of the cable to determine the resistance. The DCR verification first tests individual pins, VBUS and GND, and then tests the total DC resistance on the entire cable as a whole.

Verify Accuracy of Cable Characteristics in the E-Marker

E-Marker Verification

An E-Marker, or electronic marker, is essentially an integrated chip within a USB Type-C active or passive cable that possesses the cable’s characteristics and specifications. It is critical upon interaction between a cable and device, as it helps confirm that there is a safe exchange in data and power between the two. The E-Marker provides the cable characteristics including the cable length, the maximum supported current and voltage, the type of USB signal, the vendor and product ID, any alternate mode support, and much more.

Cables that do not go through the E-marker verification process can consequently incorporate inaccurate circuitry that portrays misinformation regarding a cable’s capabilities, resulting in an erroneous and sometimes dangerous transfer of information.

To prevent this outcome, the Advanced Cable Tester v2 verifies the validity of any E-Marker present within the cable. It reads the data of the E-Marker and then validates the advertised data and power capabilities against the actual measured parameters of the cable. Testers can easily view that these characteristics are indeed correctly advertised within the E-Marker:

  • Product: Product type as specified in the ID Header VDO. Can be either passive or active cable
  • Speed: USB SuperSpeed signaling support as specified in the Cable VDO. Can be USB 2.0 only, USB 3.1 Gen 1, or USB 3.1 Gen 1 and Gen 2.
  • Current: VBUS current handling capability as specified in the Cable VDO. Can be either 3A or 5A.
  • Vendor ID: USB Vendor ID as specified in the ID Header VDO.
  • Vendor Name: Vendor name as specified in the USB.org and the linux.org vendor lists.
  • Product ID: USB Product ID as specified in the Product VDO.
  • Test ID: USB Test ID (XID) as specified in the Cert Stat VDO.
  • HW Ver: Hardware Version as specified in the Cable VDO.
  • FW Ver: Firmware Version as specified in the Cable VDO.
  • VBUS Thru: VBUS Through Cable, either Yes or No, as specified in the Cable VDO.
  • Latency: Cable Latency, as specified in the Cable VDO.
  • Term: Cable Termination, as specified in the Cable VDO.
  • SOP DP: True if the emitter indicates an SOP'' controller is present, as specified in the Cable VDO.

Ensure Cable Performance is of Utmost Quality

Signal Integrity Testing

Signal Integrity in cables refers to the overall performance of the cable itself, so performing signal integrity tests is a vital step in quality control that should not be overlooked. Signal integrity tests within the Advanced Cable Tester v2 easily verify that the quality of the signal is within standard and there is minimal interference, which can stem from impedance mismatches, termination schemes, or transmission-line effects.

Since various data rates are supported within USB 2.0 through USB 3.1 Gen. 2 spec cables, the Advanced Cable Tester v2 tests for any High-Speed or SuperSpeed pins present to ensure each pin is providing a strong enough signal throughout the cable at the correct speed. By outputting a known-good signal on High Speed D+/D– (520 Mbps) pins and all four SuperSpeed pairs SSTX1/SSRX1/SSTX2/SSRX2 (5 Gbps, 10 Gbps, up to 12Gbit/s), the tester can measure the signal received at the other end and also confirm it was delivered on the correct pair of wires.

Eye diagrams provide users a quick visual representation of the quality of the signal within the cable. The Advanced Cable Tester v2 offers users the option to capture an eye diagram that visually exemplifies the quality of the signal in an easy-to-understand image. Typically, eye diagrams are captured using an oscilloscope that measure transmitter performance, and often, these types of tools can become very costly. The Advanced Cable Tester v2 offers a similar functionality that generates an eye diagram but at a fraction of the price. A quality-made cable will have a wider eye, while a lower quality cable will show a much smaller eye opening. This visual can provide testers a quick way to inspect each cable for such characteristics. Here is an example of a passing eye diagram:

Visual output of a passing eye diagram

For more information on how eye diagrams are beneficial in the embedded systems industry, please visit this link.

Consequences for Failing to Test Cables

Failing to test these components can result in unwanted consequences that are not only costly, but also dangerous to consumers and their safety. Read our article, “What are the Dangers of Manufacturing and Using Untested USB Cables?” to get insight into the potential consequences that can occur when neglecting to take the proper preventative testing in cables.

Want to learn more? Get more information about our Advanced Cable Tester v2 by contacting sales@totalphase.com.