Cheap Multimeter Gets Webified
[Mellow Labs] wanted to grab a multimeter that could do Bluetooth. Those are cheap and plentiful, but the Bluetooth software was, unsurprisingly, somewhat lacking. A teardown shows a stock Bluetooth module. A quick search found a GitHub with software. But then he had a fiendish idea: could you replace the Bluetooth module with an ESP32 and use WiFi instead of Bluetooth?
This was as good an excuse as any to buy a cheap logic analyzer. Armed with some logic captures, it was easy to figure out how to fake the meter into thinking a Bluetooth client was connected.
Oddly enough, the data is “encrypted” with XOR, and an AI website was able to identify the raw data versus the encrypted data and deduce the key. The rest, as they say, was software. Well, except for one hardware problem: The ESP32 needed more power, but that was a fairly simple fix.
The entire thing fit the case beautifully. Now the meter streams a web page instead of requiring Bluetooth. Great job!
If your meter isn’t handheld, you can still play a similar trick. Just don’t forget that when it comes to meters, you often get what you pay for. Not that you can’t do a similar hack on an expensive meter, either.
youtube.com/embed/IDr2Icdue40?…
hackaday.com/2025/11/12/cheap-…
