User Guide

29
CONNECTIONS
The connections for the 6-pin RS485 terminal provided (#1
on page 7) are as follows:
There is an internal short between the two A pins and be-
tween the two B pins.
The instrument has no internal line termination. To terminate
the line, an external resistor equal to the characteristic line
impedance (typically 120Ω) must be added at both ends of
the line.
Up to 32 units can be connected to the same RS485 line,
with a total line length of up to 1.2 Km using 24AWG cable.
To minimize electromagnetic interferences, use shielded or
twisted pair cable to connect the units.
Each pH502/mV602 unit is identified by its process ID num-
ber (setup item “01”).
The pH502/mV602 controller acts as a “slave” device: it
only answers to commands received from a “master” device
(e.g. an industrial PC) connected to the line.