multimeter protocol

At 50uSec I doubt that are anything.

They may be using a bit-banged serial port and that may be the software glitching the I/O port.

Get two extra serial port on your machine and run multiple copies your some terminal program at 9600 baud in hex mode.

Each serial port connected to each pin of the meter serial port.

Shouldn't be too painful.

donald

Hi Dirk,

thanks a lot for your link, the device monitoring studio did it in less than five minutes. Here are the settings for the Mastech, in case anyone should have the same problem: Baudrate: 19200

I never would have imagined this speed. The data is transmitted as plain ASCII and has the form

m is the multiplier 0 for mV, 1 times 10, 2 times 100 n are the four digits x give sign, range etc for DCV it is ;80: for pos ;

Hi Donald,

when I hooked up the scope the additional loading was already too much to stop the thing from working, so probably it wouldn't work with an extra port either, therefore I didn't even try. This is the first DMM I've seen that runs at such a high speed, I thought the 50 us were glitches as well, because the signal looks very bad, already the 104 us (now I know two bits...) are barely defined.

Daniel

Either you really screwed up your connecting the scope, or this is not RS-232.

Do as Donald suggests, that is a valid, and easy thing to do. If it doesn't work because the second monitoring port loads the device too much, then it is not RS-232.

probably it is not true rs-232, the DMM contains a photoemitter and the plug a photodiode and three transistors. Does not matter, works good enough now. With the right port settings it was easy to guess.

Thanks

Daniel