MTL2000 SERIES
isolating IS interface units

Your safe link to the hazardous area

• Mains or 24V dc supply
• 250V input/output/power supply isolation
• No high-integrity earth needed
• Broken line and earth fault protection
• Compatible with MTL3000 Series

The MTL2000 Series is the original range of MTL IS isolating devices for handling on/off or analogue signals between hazardous-area process instrumentation and safe-area control equipment. It includes IS relays for bringing back status or command signals from switches or proximity detectors, on/off units for driving solenoids, alarms or LEDs, temperature trip amplifiers, and 4/20mA analogue units which will energise and bring back the signal from a 2-wire transmitter, or drive an I/P converter.

Each design is available in three versions, 240V, 120V ac mains and 24V dc, and is mechanically compatible with the MTL3000 Series of 24V dc powered units. Both series provide an alternative to the shunt-diode safety barrier in applications where isolation is essential or preferred for its ease of application or where a high-integrity 'safety earth' is not easily available. Isolation between input, output, and power supply circuits eliminates the need to consider 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. The removal of earth requirements reduces many installation costs and enables some systems to be implemented that would otherwise be impossible. All units are certified intrinsically safe by the major authorities for connection into Zone 0, IIC, T4 (or T6) hazardous areas worldwide.

High integrity is a key feature of the series. As far as possible, each design provides protection against power supply failure, field circuit breaks and field line faults to earth. For example, a break in any of the three lines of an RTD trip amplifier de-energises the relays to give an alarm.

Two modes of earth fault protection are available. In 'fail-safe' operation, built-in relays or hazardous-area loads are de-energised by any earth fault in the field, a mode achieved simply at neglible cost by earthing one or more terminals on the unit. For critical applications, a 'no-fail' mode is available whereby field circuits remain floating while their resistance to earth is monitored by an MTL2220 earth leakage detector. The unit thus continues to operate in the event of an earth fault, the fault being brought to the attention of the operator.

Each unit is housed in a robust moulded plastic case fitted with vibration-proof terminals for field cables. Terminals can be annotated by two 18-digit rows of alpha-numeric tagging information. Where appropriate, LEDs are fitted to indicate relay status.

Units can be mounted directly on standard symmetrical 35mm (top-hat) rail, or alternatively on flat surfaces using SMC2 mounting clips. Accessories and enclosures are shared with the MTL3000 Series.

For full details of individual units refer to the individual descriptions and specifications in the following pages.

Data Sheet