Electrically-isolated Optical Link for a VC99 DMM

Connected to the Matrix

I’ve had a VC99 multimeter for a while, and one of the nice things about it, is that it can be hacked to give it RS232 output pretty easily.

The hack is possible because the VC99 uses a rather standard DMM chipset that has serial-output capabilities built-in. You can check if the feature is there by holding the REL key down for several seconds. The “RS232” indicator will appear in a corner telling you it’s sending data to its serial port.

The problem, however, is that the VC99 doesn’t have a serial port. But still, if you open the device and probe pin 92 (TXD) from the controller IC, you should be able to see the serial data being sent at 2400 bps.

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