Virtual Lab

Instruments you can drive from a browser tab

Every other page on this site works something out from numbers you type. These do something instead. The first of them talks to a bench instrument over USB — no driver to install, no vendor application, no local helper program running in the background. You plug the meter in, grant the page permission to use that one port, and the tool speaks the instrument's own protocol from JavaScript running in the tab.

That is possible because of the Web Serial API, which lets a page open a serial port after the user picks it from a browser dialog. Permission is per-site, per-device and explicit: nothing is scanned or opened without you choosing it, and the grant covers only the port you selected. As with the calculators, no data leaves your machine — the readings, the downloaded logger memory and the CSV you export are all handled in the browser, and there is no server to send them to.

What you need for the USB tools

Web Serial is a Chromium feature, so these pages work in Chrome, Edge, Opera and Brave on Windows, macOS, Linux and ChromeOS. They do not work in Firefox or Safari, and they do not work on iOS or Android, because those browsers do not implement the API at all — there is no polyfill and no fallback, since a page genuinely cannot reach a serial device without it. The tool tells you plainly when the browser cannot help rather than failing halfway through a connection.

The other requirement is that nothing else holds the port. Vendor software keeps a serial device open for as long as it is running, and the second application to ask gets an access-denied error, so close the manufacturer's program before connecting here.

Why reverse-engineered protocols end up documented here

Bench instruments frequently ship with software that only runs on Windows, only exports its own file format, and is the sole thing that knows how to talk to the hardware. When that software stops being maintained the instrument becomes much less useful than the sensor inside it deserves. Recovering the protocol from its USB traffic fixes that permanently, and writing the result down is most of the value — the working code is a few hundred lines, but knowing that a checksum is a sum rather than an XOR, or that a padding byte appears between blocks rather than only at the end, is what costs the days.

So each of these pages carries the protocol notes alongside the tool, including the specific mistakes that produce believable but wrong data. If you are porting one of them to another language, those sections are the part worth reading first.