29
INM4500-2
Mar 2009
6.3 Analogue Input modules
The analogue input (AI) modules support 2-wire or 3-wire 4/20mA or ‘smart’ transmitters located in
a hazardous area; repeating the current in other circuits to drive safe-area loads.
6.3.1 MTL4541 - Repeater Power Supply
4/20mA smart for 2- or 3-wire transmitters
The MTL4541 provides a fully-fl oating dc supply for energising a conventional 2- or 3-wire 4/20mA
transmitter which is located in a hazardous area, and repeats the current in another fl oating circuit
to drive a safe-area load. For smart 2-wire transmitters, the unit allows bi-directional communications
signals superimposed on the 4/20mA signal.
Figure 6.19
LED indicators
for MTL5541
PWR
MTL4541
1 2 3 4 5 6
7 8 9 10 1112
13 14
I
I
Vs+
Vs
2035V dc
Load
4/20mA
4/20mA
+
4/20mA
+
Safe area
Hazardous area
Terminal
Function
1
Current
input
2
Transmitter
supply
+ve
3
Common
8
Output
–ve
9
Output
+ve
13
Supply
–ve
14
Supply
+ve