INM 5500 Rev 11
42
6 .4 Analogue Input modules
The analogue input (AI) modules support 2-wire or 3-wire 4/20mA or HART transmitters located
in a hazardous area; repeating the current in other circuits to drive safe-area loads.
6 .4 .1
MTL5541/MTL5541S (-T) - Repeater Power Supply
Single channel, for 4/20mA HART® for 2- or 3-wire transmitters
The MTL5541 provides a fully-floating 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
floating circuit to drive a safe-area load. For HART 2-wire transmitters, the unit allows bi-
directional communications signals superimposed on the 4/20mA loop current. Alternatively,
the MTL5541S (-T) acts as a current sink for a safe-area connection rather than driving a
current into the load. Separately powered current sources, such as 4-wire transmitters, can be
connected but will not support HART communication.
Hazardous area
Safe area
6
5
4
3
2
1
7
8
9
10
11
12
13
14
Vs–
Vs+
20 to 35V dc
4/20mA
MTL5541
MTL5541S
–
4/20mA
Load
+
Load
+
–
–
+
Com
Tx+
Input
I
I
Terminal
Function
1
Current input
2
Transmitter ve
3
Common
10
ve via 220Ω for HART apps.
11
Output –ve (+ve current sink)
12
ve (–ve current sink)
13
Supply –ve
14
ve
Figure 6 .20:
Top labels
for MTL5541
& MTL5541S
S
