[Craig] cracked open a multimeter to unlock RS232 serial communications that can be used for data logging. There’s a couple of things that make this possible. First of all, the multimeter’s processor is not covered in a black epoxy blob, leaving the pins exposed for hacking. Second, the chip model is known and [Craig] was able to get his hands on the datasheet. One of the pins enables serial output when pulsed low. Touching it to V- even turns on an RS232 icon on the display, as seen above. To make this accessible without opening the case a momentary push button can be added, as well as connector for signal output, and a bit of parsing on the PC side to handle incoming data.