Rockwell Automation T8844 Trusted 40 Channel Analogue Input Versatile FTA - Manual (Page 7)

Trusted
TM
Analogue Input Versatile FTA T8844
Issue 4 Sep 05 PD-T8844 7
1. Description
The Trusted TM 40 Channel Analogue Input Versatile FTA T8844 provides termination for a maximum of
40 input channels from various types of field devices which generate an analogue signal in the range of
0-20mA. The 40 channels are arranged in five power groups each comprising eight identical channels.
Figure 2 below shows the configuration of a single channel within a group.
Figure 2 Single Channel Schematic
Each power group is supplied from dual 24V dc feed which are ‘commoned’ via diodes on the VFTA.
The supply is then fed to each channel within the group
The supply voltage to the field is fed via the 315mA fuse. The incoming signal (0-20mA) from the field
device is fed through the 50mA fuse which effectively limits the input signal. The voltage developed
across the 250R resistor (high precision 0.1%) is used by the input module to detect the field device
status.
The cable linking the 40 channels on the input module to the VFTA is terminated at five 10-way
connectors (TBG1 to TBG5). SmartSlot signals from the module are connected to a single 7-way
connector (TBGSS). The dual 24V dc power supplies are connected to the VFTA via five 4-way
connectors (TBFP1 to TBFP5). Forty 3-way connectors are used for the field loops (TB1 to TB40).