Rockwell Automation Publication 1734-UM013N-EN-P - September 2017 71
Install the Module Chapter 4
Safety Analog Input Wiring
The following sections contain important guidelines for wiring safety analog
inputs and wiring examples for the 1734-IE4S module.
Guidelines for Wiring Safety Analog Inputs
Follow these guidelines when wiring your safety analog inputs.
For eight terminal connections, either the 1734-TOP or 1734-TB terminal base
can be used. For all 12 terminal connections, only the 1734-TOP3 base can be
used. When using a 1734-TOP3 base, both of the COM terminals and both of
the Sensor Power terminals for each channel are internally connected. The FE
terminal connection that is shown on the diagrams represents a grounding lug on
the panel or terminal connection to the DIN rail.
If the sensor has a digital output for use with Tachometer mode, it must be either
a push-pull type output or have appropriate pull-up or pull-down resistors for
NPN or PNP sensors. The analog input module does not provide the low
impedance of these pull-up or pull-down resistors.
See Figure 47
and Figure 48 on page 78 for examples.
You must verify the behavior of your 3-wire sensor to make sure that if it loses
its ground connection, the signal is 0 (safe state) at the module input when the
fault occurs.
To obtain SIL 3, Cat. 3 or Cat.4, you must make sure that the analog input
signals cannot short together or that the two sensors are installed to provide
signals that are offset from one another. When the module is configured as the
source for sensor power, a short-circuit is detected at powerup (Cat. 2).
However, when an external power supply is used, another means must detect
this fault.
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