Wiring The Input Connectors; Input Connector Wiring - Siemens SIMATIC 505 Installation And Operation Manual

Configuring the Module (continued)
Wiring the Input
Connectors
2-8 Installlation
Thermocouple input signals are accepted through a fixed wire press in
connector block located on the front of the module. Consult the
thermocouple manufacturer's recommendations for selecting the input wire
type and size. The front connector accepts wire from 18 to 30 AWG.
The SIMATIC 505–2556 uses a fixed connector to terminate field wiring.
This is used because the chemistry of a removable connector may have an
adverse effect on the accuracy of the measurement. Siemens has carefully
selected a connector that minimizes this effect.
To assign an input to a specific channel, locate the appropriate channel
position on the connector as shown in the following figure. Wires must be
inserted by pressing the wire into the connector receptacle. To remove the
wire use a small screwdriver to depress the connector lever. Then remove
the thermocouple wire.
On each channel input the positive lead for the thermocouple is attached to
the Cn+ terminal and the negative lead is attached to the Cn– terminal. If a
shield is used it is attached at the Gn terminal. The "red" lead is always the
negative lead for thermocouples.
Figure 2-3 Input Connector Wiring
SIMATIC 505–2556 Installation and Operation Guide