XNX Universal Transmitter - Merkantile

XNX Universal Transmitter• Release Date: August 24, 1999 titled FSK Physical Layerspecification.®• The physical layer is tested according to HART PhysicalLayer Test Procedure, HCF_TEST-2.®• This specification also caters for HART Ver 6.0.• Data transfer rate: 1200 bps.HART ® devices can operate in one of two configurations - point-topointor multidrop.Point-to-Point ModeIn point-to-point mode, the 4–20 mA signal is used to communicateone process variable, while additional process variables, configurationparameters, and other device data are transferred digitally via HART ®protocol (Figure 2-24). The 4–20 mA analog signal is not affected bythe HART ® signal.Multidrop ModeThe multidrop mode of operation requires only a single pair of wiresand, if applicable, safety barriers and an auxiliary power supply forup to 8 field devices (Figure 2-25). All process values are transmitteddigitally. In multidrop mode, all field device polling addresses are >0,and the current through each device is fixed to a minimum value(typically 4 mA).Control System orOther Host ApplicationHandheld TerminalMultiplexerControl Systemor Other Host ApplicationInput/Output (I/O) SystemNote: Instrument power is provided by an interfaceor external power source that is not shown.BarrierField DeviceNote: Instrument power is provided by an interfaceor external power source that is not shown.Handheld TerminalFigure 2-24. Point-to-Point Mode of OperationField DevicesFigure 2-25. Multidrop Mode of OperationNoteUse multidrop connection for supervisory control installationsthat are widely spaced, such as pipelines, custody transferstations, and tank farms.In general, the installation practice for HART ® devices is the same asconventional 4-20mA instrumentation. Individually shielded twisted paircable, either in single-pair or multi-pair varieties, is the recommendedwiring practice. Unshielded cables may be used for short distances ifambient noise and cross-talk will not affect communication.Section 2 - Installation and Operation 2-232.3 Options