32
INM4500-2
Mar 2009
6.3.4 MTL4544B - Repeater Power Supply
4/20mA smart for 2- or 3-wire transmitters
The MTL4544B provides fully-fl oating dc supplies for energising two conventional 2-wire or 3-wire
4/20mA or ‘smart’ transmitters located in a hazardous area, and repeats the current in other circuits
to drive two safe-area loads. For smart transmitters, the unit allows bi-directional transmission of
digital communication signals superimposed on the 4/20mA signal so that the transmitter can be
interrogated either from the operator station or by a hand-held communicator.
Figure 6.22
LED indicators
for MTL4544
PWR
MTL4544
Hazardous area
Safe area
1 2 3 4 5 6
7 8 9 10 1112
13 14
I
I
I
Vs+
Vs
2035V dc
Ch 1
Load
4/20mA
+
+
Ch 2
Load
+
+
Ch 1
Ch 2
4/20mA
4/20mA
Terminal
Function
1
Ch1 current input
2
Ch1 transmitter ve
3
Ch1
common
4
Ch2 current input
5
Ch2 transmitter ve
6
Ch2
common
8
Ch1 output –ve
9
Ch1 ve
11
Ch2 output –ve
12
Ch2 ve
13
Supply
–ve
14
Supply
+ve
Note: Safe area outputs
are referenced to PSU –ve
Hazardous area
Safe area
The MTL4544B can also be used to drive two safe-area loads from a
single 2-wire transmitter (i.e. 1 in, 2 out) by interconnecting the input
channels as shown in the diagram here.
Note: In this mode the HART data is transferred via channel 1 output
only.
1 2 3 4 5 6
+
4/20mA
