29
CONNECTIONS
The connections for the 4-pin RS485 terminal provided (#1
on page 7) are as follows:
The instrument has no internal line termination. To terminate
the line, an external resistor equal to the characteristic line
impedance (typically 120
Ω)
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
HI21/HI22
unit is identified by its process ID number
(setup item “01”).
The
HI21/HI22
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.