When I learned that there were multimeters out there that had documented serial protocols I added that to my todo list for XTension support. I bought this one from radio shack more than a year ago and never got around to looking at it in any detail. Now with the kids just starting back at school and having just unearthed the protocol docs it was time to do something about it while I refreshed my memory on the code I haven't touched in months while I played with the kids over the summer. This is just first light, it's not quite beta ready yet but it's talking to XTension and updating a unit value in the database for the displayed value. Here is my Radio Shack model 22-812 multimeter with an FTDI usb/serial adaptor sticking out of the top and a View in XTension showing the value.
Still on my to do list is a significant change value that can be set, otherwise you will get a lot of updates at higher resolutions. This is just measuring line voltage here and it's bouncing around a couple of tenths of a volt constantly. So being able to set that will help. Additionally I could do some conversion to handle the auto-ranging... Or just recommend that if you're likely to change ranges while you are reading something to turn off auto ranging. The way the protocol works it just sends the display characters, not an ultimate voltage or reading. So this display might be volts or millivolts or ohms or megaohms or milliohms... This can read out anything that the meter can read so you might use it for temperature or with a clamp on current transformer or something. One thing I have noticed is that the auto-off feature to save the battery seems to be turned off when logging to the serial port. This is good because it means you could power it with a 9v wall wort replacement and it will keep running and not shut itself down.
We shall see how useful it turns out to be for me. In the meantime if you want to play with it before I get around to an official beta please drop me an email and I can send you the new builds that include support for it.