INTRODUCTION

Application and function

The Analogue Input module types MTLx541A/MTLx541AS (single channel) and MTLx544A/MTLx544AS

(dual channel) are intrinsic safety isolators that interface with process measurement transmitters located

in a hazardous area of a process plant. They are also designed and assessed according to IEC 61508 for

use in safety instrumented systems up to SIL 2.

The MTLx541A provides an input for a separately-powered 4/20mA transmitter located in a hazardous

area, and repeats the transmitter current into a load in the safe area. The MTLx544A supports two

identical channels for use with two separate transmitters. The MTLx541AS and MTLx544AS versions act as

a current sink for the safe area connection rather than driving the current into the load.

All the modules allow bi–directional transmission of HART communication signals superimposed on the

4/20mA loop current, so that the transmitter can be interrogated either from the operator station or by a

hand held communicator (HHC).

There are no configuration switches or operator controls to be set on the modules. These modules are

members of the MTL4500 and MTL5500 range of products.