Siemens SIPART DR21, Manual

Page: 128 / 242

4 Installation
4.2 Electrical Connection
Manual
128
SIPART DR21
C73000-B7476-C143-08
(1) Mains plug
(2) Power supply module
(3) Slot 1 AI3 (UNI, I/U, R)
(4) Slot 2 AI4 (UNI, I/U, R)
(5) Slot 3 5DI; 2DI 4DO; 2DO rel.
(6) Slot 4 SES (serial interface-,
PROFIBUS)
(7) Ground screw of the backplane module
(8) Fastening screw
(9) DIN rail, not included in the scope of deli-
very (accessories coupling relay module)
(10) Terminal block 1 AI1 to AI2 (I/U)
(11) Terminal block 2 AO; DI1 to DI2;
DO1 to DO2 24 V;
L+; M
(12) Terminal block 3digital outputs
±
Δ
y
(6) (5) (4) (3)
(7)
(8)
(10)
(9)
(11)
(12)
(2)
(1)
Figure 4-8 Controller backplane with terminal assignment of the standard controller
.
NOTE
The screw-type terminal blocks for connecting the process signals to the con-
troller are of the plug-in type.
D
Zero-Volt-system
The SIPART DR21 controllers only have a 0V-conductor (ground, GND) on the process side
which is output double at terminals 11 and 12 of the standard controller. If these GND-
connections are not sufficient, additional proprietary terminals can be snapped onto the DIN
rail on the power pack. The controller uses a common GND-conductor for both inputs- and
outputs, all process signals are referred to this point.
The GND-connection is also connected to vacant terminal modules. These may only be
used if practically no input current flows through this connection (see e.g. figure 4-17,
page 133).
The power supply connection is electrically isolated from the process signals. In systems
with unmeshed control circuits, the SIPART DR21s need not be interconnected. In meshed
control circuits the GND-connections of all controllers must be fed singly to a common
termination or the continuous GND-rail with a large cross-section. This common termination
may be connected with the system’s PE conductor only at one point.
The signal current is tapped at the analog signal inputs by a four-pole measurement on the
input measuring resistor. Voltage dips on the supply lines therefore have no effect. In the
case of digital signals, the signal-to-noise ratio is so great that voltage dips on the GND-rail
can be ignored.