Rockwell Automation T8834 Trusted 20 Channel Isolated AI/DI FTA External Power - Manual (Page 7)

Trusted
TM
AI/DI FTA External Power T8834
Issue 2 Aug 06 PD-T8834 7
1. Description
The Trusted TM 20 Channel Isolated Analogue Input FTA, T8834, provides termination for a maximum
of 20 input channels from various types of field devices which generate a current loop signal. When
used with a Trusted
TM T8433 TMR Isolated Analogue Input module each of the inputs is individually
isolated. Figure 1 below shows the configuration of a single channel.
Figure 1 Single Channel Schematic
The FTA is configured so that the 4-20 mA field current loop signal passes through the 100R presision
sense resistor. This converts the current loop into a voltage, measured by the module on CON1
(VSENSE). A supply of power is passed through the zener diode to provide 7.5V DC low current power
supply to power the isolation amplifiers on the input module (VPOWER).
TB1 terminals A and B are the usual connection points for the field current loop. TB2 terminals + and –
are used to provide power to the field device. TB3 terminals + and – are used to provide isolated power
supplies to each channel from within the panel.
The connector linking the 20 channels on the input module to the FTA is terminated at CON1 which is
a 96-way socket. Two rows of screw terminal connectors (TB1 and TB2) are used to connect the field
wiring.
TB1 A
TB1 B
100R
7V5
CON1 VPOWER
CON1 COMMON
CON1 VSENSE
TB2 +
TB3 +
TB2 -
TB3 -
4K75