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driver for the cheap digital multimeter VC 840/VC 820

Software for the multimeters vc840/vc820

Software for reading the data from the cheap digital multimeter VC 820 (about 50 EUR in 2007) or VC 840 (=VC 820 + True RMS, about 85 EUR in 2007) from with posix commands via a serial port.
They can be combined e. g. with the clamp-on ammeter VC 601 (about 69 EUR in 2007).
Tested with Linux, should work with every posix conforming operating system and Cygwin.

digital multimeter

The digital multimeter (DMM) can be powered from the USB bus, instead from battery, but the ground of the USB is not the ground (COM) of the DMM input. The ground of the DMM input has a negative voltage.

The MS-Win program provided with the DMM, is very poor and produces binary data files like

  • Ut70bdb.PX
  • Ut70bdb.DB

and you need special software to get the data in CSV format or read them with a program like MS-Excel. The DB file can be read from MS-Excel, but only with problems like no time.
Conrad offers the DMM PROFILAB SOFTWARE for around 36 EUR which should not have these problems.

GNU-Software for a MAS-345 or a Digitek-4000 multimeter connected through an RS-232 port can be found here:
and the multimeters of type Metex M-4650CR are similar, also at 1200 Baud:

With my first USB-RS232 (USB to Serial Adapter) adapter with an Pl2303 (driver pl2303) i've got the problem that this adapter does nothing after somes hours and a user (Stephan R.) reported defect checksums and lost bytes with such an adapter while communication works without problems with an onboard serial port.
I'm now using an USB to Serial Adapter with an FTDI chip (driver ftdi_sio, chip FT232BM) without problems.