Rockwell Automation T8831 Trusted 40 Channel Analogue FTA Non-incendive - Manual (Page 7)

Trusted
TM
Analogue Input FTA T8831
Issue 6 Sep 05 PD-T8831 7
1. Description
The Trusted TM 40 Channel Analogue Input FTA Non-incendive T8831 provides termination for a
maximum of 40 input channels from various types of field devices which generate an analogue input.
Figure 2 below shows the configuration of a single channel.
Figure 2 Single Channel Schematic
The supply for the field is derived from dual 24V dc feeds which are ‘commoned’ via diodes on the
FTA. Indication of of the presence of the power supply is provided by a green LED. The supply is then
fed to each channel.
The supply voltage to the field is fed via the 145R resistor. This effectively limits the current in the field
loop allowing inputs from nonincendive field devices located in hazardous areas. The voltage
developed across the 250R resistor due to the incoming analogue signal from the field device is fed
directly to the analogue input module.
The cable linking the 40 channels on the input module to the FTA is terminated at the 96-way socket
SK1. The dual dc field power supplies are connected to the FTA via a 5-way terminal block PWR TB.
The input signals from the field (40-off) are connected by 2-wire arrangements terminated on 12-off
3-way terminal blocks and 2-off 2-way.