Linux Data Acquisition Tool and
Optocoupler Driver for the
V&A VA18B Multimeter
This is a litte data acquisition tool for the V&A VA18B multimeter connected
to a Linux PC via the provided USB optocoupler.
While the first version of this software also contained a hardware driver for
the USB optocoupler, this is not needed anymore. Recent kernels should come
with a driver called "spcp8x5" that gives you a TTY device as soon as the link
is connected to your USB host. From version 0.2 on this software is based on
that kernel driver and does not contain the old driver anymore. If you need
the deprecated driver, please use version 0.1.
To get the initialization of the SPCP825 based optocoupler working, I had to
sniff and analyse the communication of the 'Sunplus RS232C to USB Adapter'
Windows driver. If you put your multimeter in the PC-LINK mode, you can read
out the binary state of the LCD cells via the optical port. The transcoding
to a human readable output format is done by the provided data acquisition
tool called 'multimeter'. It is a simple Perl script that reads the encoded
data from a given TTY device (defaults to /dev/ttyUSB0) and writes tab
seperated values of the measured data to stdout.
So far the software has only been tested with a V&A VA18B on Linux, but chances
are that some other mutlimeters (e.g. PeakTech 3375) and Unixes will be
compatible as well.
You do not need to, but you might want to install the tool system-wide:
$ sudo make install
Connect your multimeter to the PC and just run 'multimeter' without any
argument. As soon as you put the multimeter in the PC-LINK mode, the data
acquisition tool will start to dump the measured values along some other data:
||passed seconds since the acquisition has started
||unit: [u|k|m|M] (%|Ohm|A|V|Hz|C)
||flags: AC, DC, auto, diode_test, cont_check, rel, hold, min, max
To stop the acquisition press Control-C. To write the data to a file, you
have to redirect stdout accordingly.
If you want to connect several multimeters to your PC in parallel, you have to
call the tool with an argument that gives the full path to the corresponding
Note: you can leave your multimeter in the PC-LINK mode, while running
'multimeter' several times.
$ multimeter > test.dat
And if you want to log the data of two multimeters in two different files at
the same time:
$ multimeter > test1.dat & multimeter /dev/ttyUSB1 > test2.dat