New USB-C Charging Meter from Plugable

USB-C charging demystified.

One of USB-C’s great potential features is the ability to charge in either direction, with much higher power levels than was previously possible with USB (up to 100 Watts). But USB-C is still maturing, and there are many combinations of chargers and devices which either don’t charge, or charge at a lower rate. And if you’re a hardware designer or tester you need to be on the lookout for unexpected results or problems. Plugable’s new USB-C power meter is an inexpensive solution.

The USBC-VAMETER is a compact USB-C multimeter designed to quickly show how your USB-C devices are behaving under a variety of scenarios.

The Plugable USBC-VAMETER is roughly the size of the average USB flash drive and was designed with portability and ease of use in mind, only showing essential information that users of all skill levels can understand. With three major points of information the VAMETER can quickly show how fast a device is charging by indicating voltage, amperage, and in addition the direction in which the electrical current is flowing. Users can calculate how much power a device using this simple formula: The power P in watts (W) is equal to the voltage V in volts (V) times the current I in amps (A), P = V × I.

Here you can see that the voltage is reported as 14.5V and the amperage is 1.77A which calculates to 25.66 watts. This would indicate that the system is charging at almost the maximum rate (29W for the model system the USBC-VAMETER is attached to).

The VAMETER is bidirectional and can be connected in any direction and it will indicate in what direction power is flowing. This is useful when you’re not sure if a device is drawing power, or pulling power. We took special care when designing this product to ensure that it acts as a transparent interposer – which means it should not interfere with the USB data (1.1 through 3.1 Gen 2), USB-C Alternate Mode video, or USB-C charging. It can be used inline with USB-C docking stations, chargers, USB-C accessories, etc. The meter is able to achieve this without interfering with normal USB-C operation as it only taps into the power (VBUS) and ground connections to measure their values and leaves all of the data lines untouched.

Common use scenarios would include the following:

  • Connecting between a USB-C host system like a laptop, tablet, or cell phone and a charger to monitor charge information.
  • Connecting between a USB-C host and docking station to monitor charge information.
  • Connecting between a USB-C host system and a USB-C bus powered accessory like an external hard drive, flash drive, etc to measure power draw of a device.
  • Testing for USB-C port spec compliance such as a VBUS hot condition, voltage drop under load, etc.

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