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 Asset Management with HARTHART—an established standard in process automation The HART communication protocol is well established on the market. It is part of today's generation of 4-20 mA devices for standard fitting and is present in more than two thirds of all newer systems. HART information is available for use via the option of conventional access by using handheld terminals on-site on the devices or by HART multiplexer. HART multiplexers are used to retrieve digital HART information. They are connected to the 4-20 mA lines and thus form an independent lower-tiered service level that can be used to retrieve digital information including the process value (which is also available in digital format) and then digitally transfer it on to the process control system or to a control tool. Analogue signal transmission and processing of the measurement value by the PCS (process control system) are in no way affected. HART multiplexers are ideally suited for evaluating Information from complex sensors and actuators in systems that were equipped with field device systems based on 4-20 mA HART technology five or ten years or even longer ago. The HIS MUX 2700 and KFD2-HMM16 systems of Pepperl+Fuchs can be used together with control interfaces such as PACTware™ to provide digital access to the configuration and diagnostic data of HART field devices. Multiplexers are connected with the automation device via a RS 485 interface. Online access to up to 7,936 diagnostic data items The HART KFD2-HMM-16 multiplexer works as a master-slave system. In its maximum configuration, it can operate up to 256 analogue transmitters or control devices that support digital communication based on the HART specification. The slave unit integrated into the master controls the first 16 channels. As many as 15 additional KFD0-HMS16 slave units can be connected to the master unit. Each of these slave units in turn can support an additional 16 channels. With the system assigned, one master can thus operate 256 field devices. Up to 31 KFD2-HMM-16 master units can be connected to an RS 485 interface. Since each master can address up to 256 field devices, a maximum of 7,936 field devices can be operated with each RS 485 interface.  HART multiplexer for up to 7,936 field devices: KFD2-HMM-16 Flexible application areas The MUX2700 multiplexer is used worldwide in projects of all sizes. It has been tested for compatibility and approved for use with AMS Asset Management Systems and Valve Link of Emerson Process Management. Each multiplexer allows for communication with 32 HART devices with a device width of only 18 mm. A network can be set up via an RS 485 interface with a total of 31 multiplexers. This makes it possible to query up to 992 field devices. The MUX2700 offers complete "3-port insulation“. Each input channel decouples the HART signal and ensures absence of side effects.  HART multiplexer for Asset Management Systems: MUX2700 Systems for applications with requirements Field installation from devices and point-to point connections to the automation device can be retained without changes when using the KDF2-HMM-16 and MUX2700 HART multiplexer. HART multiplexers are simply connected to the existing 4-20 mA lines. Multiplexers act as transparent gateways and assume the task of routing communication between the control and maintenance station and the HART field devices. The maintenance station can address up to 31 multiplexers via an RS 485 connection running at up to 38,400 Baud. In accordance with the RS 485 specification, the length of the line can be up to 1200 metres. Networks can be set up with additional serial interfaces to the PC. This makes it possible to connect any number of devices virtually to a single Asset Management System. The modem for modulating the HART signal is integrated into the multiplexer. HART multiplexers support devices of HART version Rev. 6.0.
They conduct an automatic search of all connected HART field devices with (Rebuild), read device information and save it in an internal database. This information is made available to the higher-level control tool. A SCAN function that can be activated in the multiplexer allows the multiplexer to read HART data from field devices cyclically. Multiplexers can act as primary or secondary masters (for example a manual control device). The control station software can be used to access the HART parameter of the multiplexer. The extension to OPC server software of the HART Communication Foundation ensures additional compatibility. This makes it possible to program user-designed applications for special requirements. Commands from the control and maintenance station are passed through without any changes for communication with transmitters and HART control devices. These commands are given their own configuration parameters, just like other HART field devices, to identify and set parameters for multiplexers. Configuration parameters
Device variants Multiplexers appear as HART devices themselves with a special device description (DD) created for that purpose and their own device manager (Device Type Manager, DTM); This ideally meets the requirement for integration into modern Asset Management Systems. Field devices can be controlled by flexible interface and motherboards in versatile customer-specific designs. Boards make the HART connection available for the multiplexer. Connections to the process control system can be designed either with special control system connectors for the system cable leading to the PLS or for flexible individual wiring. The small size, low cost per point-to-point connection and the small installation dimensions play a special role in converting installations. Switch cabinet space is expensive and frequently is not available. A wide range of interface and motherboards are available for new installations for use instead of I/O console of the process control system. They can also be mounted directly on the multiplexers. Interface boards are designed for the high quality required in modern automation systems and ensure reliable signal transfer. Assessments for loop considerations up to SIL3 are available for both multiplexer systems in applications with requirements for functional safety.  Overview of performance features: KFD2-HMM-16 and MUX2700 Uniform device management Access to digital information can be used effectively if suitable tools are available. The new FDT/DTM concept for device management, which was developed as part of fieldbus technology and is considered very forward looking, has therefore been adopted for HART multiplexers as well. It consists of:
PACTware™ configuration tool PACTware™ is a control interface for uniform non-manufacturer-specific parameterisation and configuration of field devices, remote I/O systems and communication modules in fieldbus systems. PACTware™ has a communication interface based on the FDT standard and is therefore designated as an FDT frame application. PACTware™ allows for access to HART multiplexers and all HART field devices provided a technical description is available for each device in the form of a DTM. A generic HART DTM is also available in PACTware™. It can be used to set parameters of HART-capable field devices for which there are no special manufacturer DTMs. The universal and standard commands based on the HART specification that are used by most HART devices on the market are also supported by the generic DTM. PACTware™ supports a wide range of functions, including status monitoring and messages, interactive functions and graphical objects such as trend graphs, echo curves, time graphs or device-specific online help, all integrated into the corresponding DTM.  PACTware™ user interface Ideal solution for modernisation projects HART is the worldwide available standard for communication with intelligent field devices for process control in process automation. HART multiplex systems are ideally suited for system modernisation, renovation and expansion. HART multiplexers are able to make full use of the performance capacity of HART field devices already installed in systems. HART multiplexer give personnel placing systems in operation or repairing and maintaining them central access to detailed device information. This is needed to reliably access the status of the system.
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