Panametrics DigitalFlow GS868, Programming Manual, Page: 85 / 146

DigitalFlow™ GS868 Programming Manual (2-Channel) 75
Chapter 6. Serial Communications
6.5 Optional RS485 Serial Interface
Although the standard RS232 serial interface included with the Model GS868 is adequate for most applications,
Panametrics offers an optional RS485 serial interface upgrade for special situations. The Model GS868 is easily
modified to provide RS485 communications, and this section describes the wiring and use of the special RS232 to
RS485 converter.
IMPORTANT: This section refers to the PC communications port (labelled “RS232” on the main board). If you have a
MODBUS card installed, the terminal block on that card will always be RS485. The MODBUS card only
sends MODBUS data and cannot be used to set up the GS868. IDM communication always passes via
the RS232 port described here.
Note:
For compliance with the European Union’s Low Voltage Directive, this unit requires an external power
disconnect device such as a switch or circuit breaker. The disconnect device must be marked as such,
clearly visible, directly accessible, and located within 1.8 m (6 ft) of the electronics console.
6.5.1 Interface Converter Mounting
A special bracket containing the serial interface converter and a three-terminal barrier strip is mounted inside the
Model GS868, just below the RS232 terminal block (see Figure 9 below). The standard RS232 terminal block is wired to
the input of the serial interface converter, and the RS485 output of the serial interface converter is wired to the barrier
strip.
Figure 9: Interface Converter Mounting
6.5.2 Point-To-Point Wiring
Standard factory wiring of the RS485 serial interface is configured for point-to-point wiring. That is, a single Model
GS868 may be wired directly to a single personal computer. To connect the RS485 serial interface, refer to Figure 9 on
page 75 and complete the following steps:
Note:
For compliance with the European Union’s Low Voltage Directive, a transparent plastic shroud protects the
electrical connections. The shroud must remain in place, except while wiring the unit. Reinstall the shroud
after the wiring has been completed.
RS 232
T T
T R
T
S N R
X X
C D R
DN
CHAN 1
G
I
S
G N N
S
I
R
T
R
T
UP
D
C
R
S
- XMT +
Red (XMT+)
RS232 Terminal Block
Standoff
Mounting Bracket
Barrier Strip
LVD Shroud
Green (XMT–)
Grounding
Screw
G N/L2 L1 AC
G – + DC