Operating Instructions
ISD 230/260/280 IR Data Transmission Systems
Chapter
5
© SICK AG · Auto Ident · Germany · All rights reserved
8 008 207/30-11-2001
30
Electrical installation
Line termination (RS 422/485)
RS 485:
If one of the ISD 230 units is the last device at the line end of the electrical bus, the unit
can be terminated. A defined line termination is then connected internally for the receiver
in the unit to enhance the signal-to-noise ratio.
The terminating resistors can be integrated in the line with the DIL switches S1.7 and S1.8,
as shown in
Table 5-2, Page 25
. The resulting circuit is shown in
Fig. 5-5
.
RS 422:
In this point-to-point configuration, the terminating resistors must be connected to the
receivers on both stations.
Last device
at end of bus
R+/T+
or B
*)
R–/T–
or A
*)
Receiver
S1.8 (Term–)
S1.7 (Term+)
ISD 230
Host
ISD
ISD
➚
. . .
RS 485
+5V
390
Ω
390
Ω
220
Ω
6
7
GND
Konfiguration
und
elektrisc
he
Installation
ISD
230
Fig.
5-5: ISD 230: Line termination for the RS 485 interface
5.1.7
Connecting the functions interfaces
The ISD 230 is equipped with two switching outputs and one switching input per unit.
These have the following functions:
•
A signal level of +24 V is pending at the “Light path free“ switching output if the light
path is free and light reception from the opposite station is adequate. If the light path is
interrupted completely, e.g. due to an obstacle, or if the intensity of the light received
from the opposite station is too low due to an object in the light path or because the
distance between the two stations is too large, the output is disabled (signal level 0V).
This output has the same functionality as the “Light path interrupted“ LED at the top of
the front panel on the device but does not flash in the transition range.
•
A signal level of +24 V is pending at the “Contamination“ switching output under good
transmission conditions and indicates that reception is adequate.
If the intensity of the light received from the opposite station is not adquate, e.g. due to
contamination on the reception lens caused by dust deposits, the output is disabled
(signal level 0V).
Configuration
and
electrical
installation
of
the
ISD
230
*) to EN 50 170