USB C Cable Tester
Downloads
- User Guide (PDF)
- A brief user guide that includes the specifications of the device.
Topics
The “USB C Cable Tester” verifies the wiring and capabilities of a USB C cable; that is, any cable with either two USB C connectors, or a combination of a USB A and a USB C connector. On the outside, USB C cables look alike. Internally, though, some may have as few as 2 individual wires and others as many as 18 wires.
The USB C Cable Tester is therefore not only useful to check whether a cable is good or bad, but also to check what type of cable it is (what capabilities it has). Not every USB C cable is fit for every purpose.
The USB C Cable Tester is simple to use: you connect the cable to the connectors on the left and right sides of the Tester. Then you press the push button in the lower right corner (with the label “Test”). One or more LEDs will light up, telling you the cable type and whether any fault was detected.
If the cable has a USB A connector on one end, you connect it to the connector on the left side, and the USB C connector to the right side.
| USB 2.0 / 1.1 | Up to 480 Mbit/s data transfer (low speed, full speed and high speed). |
| USB 3+ Single Lane | A “SuperSpeed” cable with up to 5 Gbit/s (USB 3.0, or USB 3.2 Gen 1×1) or 10 Gbit/s (USB 3.1, or USB 3.2 Gen 2×1) transfer speed. |
| USB 3+ Dual Lane | A “SuperSpeed+” cable with up to 20 Gbit/s (USB 3.2) transfer speed or higher (USB4). |
| Power Delivery | If this is the only LED that lights up, it is a charging cable (no data transfer). Otherwise it indicates a cable with a higher power rating. See “USB Power Rating” below. |
| Audio Accessory | The cable supports the analogue sideband channels. These are used by some audio devices or headsets. |
| Non-Shielded | When full on, the cable is not shielded. When blinking, it is either improperly shielded or unshielded. See “Cable Shielding” below. |
| Fault | When full on, the cable has a broken wire or an internal short. When blinking, the cable is not standards-compliant, but may still function (at lower transfer speeds). |
As for the USB cable, the “lanes” are additional communication lines (for which the cable has extra wires). The original USB specification (version 1.0 up to 2.0) used a single differential pair of wires for bidirectional (half-duplex) communication. USB 3.0 introduced an additional full-duplex “lane” for SuperSpeed (adding four wires into the cable). USB 3.2 added a second lane (so 4 wires more in the cable).
What makes this confusing, is that the naming of the USB standards has changed.
- The original USB 3.0 standard is now called USB 3.2 Gen 1×1.
- The original USB 3.1 standard is now called USB 3.2 Gen 2×1 (this still uses a single lane).
- The original USB 3.2 standard is now called USB 3.2 Gen 2×2 (dual lane).
The power rating of a USB cable is convoluted, and depends (among other things) on the connectors.
Cable with two USB C connectors
Any cable with two USB C connectors must be rated to at least 60 Watt
(20V × 3A). When the “Power Delivery” LED is on, the cable
is rated 100 Watt (20V × 5A) or possibly higher.
The exception is for a charge-only cable (when the “Power Delivery” LED is the only LED that lights up). In that case, the rating must be assumed 60 Watt.
Cable with USB A to USB C connectors
When the “Power Delivery” LED is off, the cable must be assumed
15 Watt (5 V × 3 A). When the LED is on, the power rating is 60 Watt
(20 V × 3 A) or possibly higher.
For a charge-only cable (when the “Power Delivery” LED is the only LED that is on), the rating must be assumed 15 Watt.
For reliable communication at the maximum transfer rates, the various USB standards mandate shielded cables. The cable tester therefore tests the connection between the connector shields. When the Non-Shielded LED blinks, the cable tester cannot determine whether the cable is shielded, because the connector shielding is shorted to ground at both plugs.
Whether or not it is a good idea to short shielding to ground, depends on the devices. For a device in a metal enclosure, the shielding should be connected to the enclosure, so that the enclosure and attached cable still form a Faraday cage. Connecting shielding to ground, in this case, pierces a hole in the Faraday cage and reduces the shielding efficiency. For a device in a plastic enclosure, this does not apply: there is no Faraday cage. Instead, connecting shielding to ground may then be the better option, both to increase the self capacitance of the system, and because a ground plane on a PCB may function as a kind-of shield.
So, there is no clear-cut answer as to whether or not the cable shielding should be connected to ground. It depends on the device that you plug the cable into. There is, however, a clear-cut answer as to whether is is a good idea to have the shorts to ground in the cable plugs: No, because that treats all devices as unshielded.
The USB C Cable Tester basically tests which wires are connected between both connectors. From that, it infers the capabilities and the USB standards that apply to the cable.
Full-featured USB C cables contain an E-marker chip inside the cable. This chip gives details on the maximum voltage, maximum current and maximum data transfer speed that it supports (plus other information, such as the manufacturer and the cable length). The USB C Cable Tester detects the presence of an E-marker chip, but does not read it out.