Once the driver is correctly installed, connecting the HM21 will add a com port to
your PC, and you can configure your PC to control or receive data over the port.
The com port number will vary depending on your PC configuration. For laptops
the com port is usually 2 and for desktops without a modem it is often 3, but these
are only a general guide and you will need to determine this yourself.
The com port settings are 9600 baud, 8 bit, no parity, 1 stop bit. Hardware and X
on/off handshaking are not used.
It should be possible to build and send small macros to set the current and zero the
reading etc from the PC.
Data output from the RM3 is in CSV format. This is the most basic format
understood by databases and spreadsheets. Some means of capturing the data into
a file on the PC will need to be used. At the most basic level, data can be captured
in hyperterminal. Save it as a text file, change the files extensions to .csv, and it
can then be opened in excel.
Even without special software, using hyperterminal it is possible to control the
HM21 and cause it to output data remotely. The remote control commands simply
mimic the operation of the keypad. They are:
“f” sets forward current
“r” sets reverse current
“s” puts the HM21 in standby mode
“z” zeros the reading
“h” sets high sensitivity mode (either 2 or more decimal places max +/- 150mV)
“l” low sensitivity (1 decimal places max +/- 1250mv)
“q” changes display from ohms/sq to mV
“o” output data through the serial or USB port
“p” decreases current
“i” increases current
“A” to “F” select the current in an absolute way as presets. It is capital letters (case
sensitive.)
5 Pin “Din” Plug
1. Current source –
RED
2. Earth
3. Current source –
BLUE
4. DVM –
GREEN
5. DVM -
YELLOW
“Screen” is earth
