Eaton MTL4850 Instruction Manual
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Contents
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DRAFT - 11 December 2014DRAFT - 11 December 2014INM MTL4850_54 Rev4 32.1 General purpose or IS?The MTL HART Management System can be used to control and maintain field devices thatare located in a safe area or a hazardous areas.For safe areas, HART Connection Units provide the necessary terminals to connect up to32 field devices. These may be basic connection units, linked to a HART interface board, orthey may be integrated units with an MTL4850 or MTL4854 multiplexer onboard. Section 2.3explains this in more detail.Hazardous-area field devices can be handled using IS isolating interfaces convenientlymounted on a backplane with facilities for onward connection to the host. Here also there is achoice of a backplane with an onboard HART multiplexer (CPH models), or legacy backplanesthat can be linked to a HART interface board that carries the multipexer(s).Having the isolators mounted on a backplane dramatically reduces the amount of hand wiringrequired and therefore reduces the number of potential wiring errors. The hazardous-areawiring terminates on the isolating modules, not the backplane, consequently the backplanesdo not need IS certification.2.2 Generic or custom?A range of generic connection units is available for both input and output field-device wiring.These are not designed for any particular DCS type and may be used universally.The alternative is to choose a connection unit or backplane that integrates with the type ofDCS being used on the plant. The key advantage of this method is the use of a DCS’s specificconnector type, which simplifies the wiring of the connection units into the system. Varioussolutions are available to suit individual DCS types and a listing of the currently availableconnection units and backplanes is given in Appendix A.2.3 Connection methodsThere are currently three methods for linking the HART signals to the MTL4850 or MTL4854:a) using an integrated connection unit – HTP-SC32 - see Figure 2.2b) via a connection unit to a HART interface (HMP-HM64) - see Figure 2.3c) using an IS isolator backplane with a HART interface - see Figure 2.4NOTEthe MTL4850/54 may also be used to update existing HART installations, but thesemethods are not discussed here. Consult MTL for information if this is of interest.The self-contained (non-IS) connection unit - see Figure 2.2 - is a 32 channel connectionunit with screw terminals for the field devices and the main system, and an integratedmultiplexers. Up to 63 of these connection units can be daisy-chained on an RS485 link to aPC runnning HART maintenance software. Apart from an RS485 to USB (or Ethernet) protocolconverter, no other external hardware is required.See Section 4.1 for details.MTL4850/54Figure 2.2self-containedHTP–SC32 |
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