LumaSense Technologies M340 - Manual (Page 17)

M340 Manual Communications Port 17
5 Communications Port
5.1 RS232C
This blackbody may have the option to communicate with the temperature controller via a PC or
similar device. The DB-9 male connector is on the rear panel. Wiring is shown below. It is wired
to operate with a standard through cable (not null modem). This method allows bi-directional
data transfer via a three conductor cable consisting of signal ground, receive input and transmit
output. It is recommended for communication distances less than fifty feet between the
computer terminal and the instrument. Note: Multiple instruments can not be connected to the
same port.
The RS232 port is optically isolated to eliminate ground loop problems. Typically, “DATA OUT”
of the computer/terminal connects to the “RCV” terminal on the instrument. “DATA IN”
connects to the “XMT” terminal. If shielded cable is used, it should be connected to the frame
ground at one end only. Signal ground is to be connected at appropriate ground terminals. A
cable and sample software are included.
RS232 Wiring
The blackbody was shipped with the controller set at the following com port parameters:
Baud: 1200
Data Bits: 7
Stop bits: 2
Parity: odd
To alter these parameters, see Section 4.4.
5.2 RS485
The RS485 multipoint capability allows up to 32 controllers to be connected together in a half-
duplex network. This method allows bi-directional data transfer over a shielded twisted pair
cable. The twisted pair cable is a transmission line; therefore, terminating resistors are required
at the most distant ends of the line to minimize reflections (typically 60 ohms from each line to
signal ground). The RS485 circuit is fully optically isolated, eliminating ground loop problems.
Parallel drops from the transmissions lines should be kept as short as possible; however, the line
may be daisy-chained at each controller. The polarity of the line is important and each device
will specify an “A” (+) and “B”(-) connection.