PowerScope

ChargerLAB only provides a Windows app for the Power-Z KM003C. I wasn’t going to install a whole separate operating system just to use one USB power meter, so I built PowerScope. It graphs live voltage, signed current, power, temperature and USB rails at up to 100 samples per second; records sessions; exports CSV and JSON; and captures and decodes USB Power Delivery traffic and cable E-Markers.

PowerScope showing live power measurements from a KM003C

PowerScope reading a KM003C directly from the browser — it’s my iPhone charging

Everything runs locally in the browser. WebUSB talks to the meter, Web Serial provides its separate control channel, Go/Wasm parses measurements and USB-PD traffic, and IndexedDB stores recordings. The site serves static assets; device data stays in the browser.

Try the web app in Chrome or Chromium.