33
INM4500-2
Mar 2009
6.4 Analogue Output modules
The analogue output (AO) modules accept 4/20mA floating signals from safe-area controllers to
drive current/pressure converters (or any other load up to 800
Ω
) in a hazardous area.
6.4.1 MTL4546/4546C/4546Y - Isolating Driver
For 4/20mA smart valve positioners with line fault detection
The MTL4546 accepts a 4/20mA fl oating signal from a safe-area controller to drive a current/
pressure converter (or any other load up to 800
Ω
) in a hazardous area. For smart valve positioners,
the module also permits bi-directional transmission of digital communication signals so that the
device can be interrogated either from the operator station or by a hand-held communicator.
Process controllers with a readback facility can detect open or short circuits in the fi eld wiring:
if these occur, the current taken into the terminals drops to a preset level. The MTL4546C and
MTL4546Y are identical to the MTL4546 except that they provide open circuit detection only (no
short-circuit detection).
Hazardous area
Safe area
P
I
1 2 3 4 5 6
7 8 9 10 1112
13 14
I
I
Vs+
Vs
2035V dc
+
+
4/20mA
Terminal
Function
1
Output
–ve
2
Output
+ve
11
Input
–ve
12
Input
+ve
13
Supply
–ve
14
Supply
+ve
Figure 6.23
LED indicators
for MTL4546,
MTL4546C &
MTL4546Y
PWR
MTL4546C
PWR
MTL4546
PWR
MTL4546Y