Rockwell Automation TAI16AIR 16-Channel Analogue Input Termination Card - Manual (Page 6)

6 TAI16AIR October 2005 – Issue 5
Triguard SC300E
EXTERNAL CONNECTIONS
Fixed Terminal Details
Chassis connector J1 Connector, 34-way, DIN41612, female
Field terminals 1 to 16(+) and 1 to 16(-) Screw terminals to suite 2.5mm 2 w i r e
(16AWG)
Field power supply inputs FS1 and FS2 Header, 2-way, Molex Minifit Jr
Alarm output PL1 Header, 2-way, Molex KK
Ground terminal TS1 Provision for M3 ring terminal
THEORY OF OPERATION
The termination card circuit comprises 16 channels each fused at 1A with a fast acting,
indicating fuse. Figure 2-3 shows the connections for Channel 1, all other channels are
identical.
The current loop field device is connected across the screw terminals 1(+) and 1(-) and
supplied with a nominal 24V via the indicating fuse F1. The 0-20mA loop current from the field
device re-enters the termination card and develops a voltage across the 250 ohm precision
resistor R1. This metered voltage is applied, via J1/2a and J1/2c, to one of the channels of a 0-
5V Analogue Input Module. Use of the precision resistor allows the output voltage to be applied
to more than one Analogue Input Module without sharing the loop current so that two modules
can be connected in parallel for ‘hot repair’ redundancy. D1 is a transient suppressor to protect
the module input against the effects of lightning strikes, etc. on the field equipment.
Any blown fuse lights the Fuse blown LED LD1 and also provides a remote Alarm output via
PL1/1 and 2.
Power for the circuit and for the field devices is from two independent supplies, nominally 24V,
at FS1 and FS2. The positive supply lines are auctioned via D17 and D18 to ensure even power
consumption. The common 0V line is connected to the negative side of all the module input
channels.
The common 0V line is also connected, via C1 and R20, to the M3 ring terminal TS1 which
should be connected to a suitable earth to prevent the channels floating if the multicore cable
to the chassis is disconnected.