Rockwell Automation T8448 Trusted TMR Zone Interface Module - 40 Channel - Manual (Page 16)

Trusted
TM
Module T8448
Issue 14 Apr 10 PD-T8448 16
1.11. Input Interfaces
Each channel selected as an input is provided with three A/D converters which monitor the voltage at
the input connection. These are the same A/D converters which are used to determine channel state
in the output configuration. Each input is a high impedance channel and measures from 0 to 30 V. If
current is to be measured, the input must be conditioned with an external resistor. This resistor is
mounted on the 8842 Versatile Field Termination Assembly. The module uses its TMR architecture to
provide fault tolerance in the event of a hardware failure. Dynamic testing of the input path is provided
to ensure safe operation within the TMR structure.
Note that 24V field power is required for a Zone Interface Module even if all channels are configured as
volt-free inputs. This may be connected via the plug at the chassis end of the cable to a T8290 or
T8297 distribution unit (for cables without power wires) or at the VFTA (for integral power cables).
1.12. Field Interface Selection
For details of the recommended field interface circuit configurations, please refer to the product
description for the 8842 Versatile Termination Assembly.