MTL3000 SERIES
isolating IS interface units

Your safe link to the hazardous area

• Full input/output/power supply isolation
• No earth required
• 24V dc or loop powered
• Mains-powered dc supply unit available
• Compatible with MTL2000 Series
• Rail or surface mounting

MTL3000 Series interface units offer a compact and easy-to-use means for communicating safely with process measuring, indicating, actuating and local control equipment in hazardous areas. A comprehensive range of models handles analogue, switch and serial-digital signals in both directions, amplifying or otherwise conditioning them as required and at the same time providing worldwide-certified explosion protection for equipment and wiring in all zones and all explosive atmospheres. The MTL3000 Series complements and extends the MTL2000 Series with which it is mechanically compatible. It also provides an alternative to the shunt-diode safety barrier where isolation is essential or preferred or a high-integrity earth is not readily available.

Key features of the MTL3000 Series are ease of application, high operational integrity and reliability, and low installed cost. Full 3-port isolation between the input, output and power supply circuits of each unit eliminates the need to think about relationships to earth, makes system hook-ups easier to arrange, and allows hazardous-area circuits to be left floating or earthed at any one point. Moreover, the fact that all models are IS without a special earth reduces the cost of many installations and enables some to be implemented that would otherwise be impossible. Since no IS earth is required, routine inspection of earth cables and connections is eliminated.
The plant operator will find other benefits, for example he can monitor plant conditions in the secure knowledge that an earth fault will be 'flagged' while the loop continues working. Floating circuits plus the MTL2220 earth leakage detector make this option possible for all switch applications and some others.

MTL3000 Series units are powered from a 20-35V dc supply, or in some cases from the signal itself. Most plants have 24V dc available, and the elimination of multiple mains transformers reduces size and weight, cuts down heat dissipation and increases reliability. Built-in dc regulation and an easily replaceable fuse guard against damage from fluctuating supplies, and all units are proof against short circuits in the field.

The dc isolation and intrinsically-safe segregation in all units are provided by small ferrite transformers with demodulators either side, in the manner pioneered by Evershed & Vignoles Ltd, but using modern low-loss materials and semiconductors to allow operation at higher frequencies. Analogue units 'chop' 4/20mA currents directly rather than voltages derived from them, so there are no 'high-stability' resistors to drift and cause inaccuracies.

Mounting of MTL3000 Series is on top-hat rail or any flat surface, using the built-in, extendable mounting clips. The units are half the width of those in the MTL2000 Series but identical in other dimensions, except for the MTL3991 power supply unit which is in MTL2000 Series format. All models share with the MTL2000 Series the comprehensive range of mounting accessories and weatherproof enclosures.

Data Sheet