Measure USB A or C Voltage with Klein USB Digital Meter ET920

ID: 219152

Description: The Klein USB Digital Meter ET920 can be used...

To check the voltage of a USB A port, simply plug the USB A cable into the power source and it will automatically read it. (Notice only voltage is displayed).
To test the current to a device (in this case a battery), plug the device into the output of the meter after the meter has been plugged into the source. Then read the meter. Now you see the current drawn as well.
For USB A, 5Vdc is the only voltage reading you should see. If the value displayed is within 10% of 5V, it is likely not a problem. The current flow will tell you how much the device is using. A 10W charger can provide up to 2A of current. A 20W charger will provide up to 4A of current.
This concludes the USB A testing

USB C can operate at several voltages from 5V up to as much as 48V but 20Vdc is pretty common. This voltmeter only goes to 20Vdc with is actually plenty for many laptops.
Plug the USB import into a power source AND plug the device under test into the USB C output of the meter. Since USB C uses smart technology to negotiate the charging voltage, it needs a device on the output to show anything.
Just like USB A, now you can read the voltage and current. In this case 9.06Vdc and 2.0A.
This completes Basic USB C port testing.

Here I am powering my 16" MacBook Pro with the USB C port. Most modern laptops can be powered from their default power input or one of their USB C ports. This comes in handy when using a generic docking station.
Notice the laptop negotiated 19.91V and it is drawing 1.1A. That's only about 22W but my battery was fully charged so it didn't draw much.
This concludes basic USB A & C Voltage testing. There are many different USB Voltmeters out there to choose from but they all have the same basic functions. I hope this guide helps you troubleshoot USB Power issues you may run into.

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