HART OverviewThe majority of smart field devices installed worldwide today are HART-enabled. But some new in the automation field may need a refresher on this powerful technology.Simply put, the HART (Highway Addressable Remote Transducer) Protocol is the global standard for sending and receiving digital information across analog wires between smart devices and control or monitoring system or Handheld communicators.More specifically, HART is a bi-directional communication protocol that provides data access between intelligent field instruments and host systems (DCS/PLC or Handheld Communicator). A host can be any software application from technician’s hand-held device or laptop to a plant’s process control, asset management, safety or other system using any control platform.HART TechnologyHART technology is easy to use and very reliable when used for commissioning and calibration of smart devices as well as for continuous online diagnostics.There are several reasons to have a host communicate with smart devices. These include:.

Device Configuration or re-configuration. Device Diagnostics.

This work presents different MAC protocols for wireless sensor networks and compares them to each other. Therefore it starts with an introduction in wireless sensor networks. It will explain the important role of MAC protocols for energy saving and why currently common protocols don't fit for the actual requirements. HART COMMUNICATION 1. The majority of smart field devices installed worldwide today are HART-enabled. But some new in the automation field may need a refresher on this powerful technology. Simply put, the HART (Highway Addressable Remote Transducer) Protocol is.

Device Troubleshooting. Reading the additional measurement values provided by the device. Device Health and Status. Much moreYears of success using these benefits explain why HART technology is the largest of all communication protocols, installed in more than 30 million devices worldwide.If you’ve ever used a land-line telephone and noticed the Caller ID display to take note of who is calling, you already know half of what the HART Protocol does—it tells “who” is calling.

In an industrial automation network “who” is a microprocessor-based smart field device. In addition to letting such smart field devices “phone home,” HART Communication lets a host system send data to the smart instrument.HART emerged in the late1980s based on the same technology that brought Caller ID to analog telephony. It has undergone continued development, up to and including automation products now shipping with built-in WirelessHART Communication.How HART Works“HART” is an acronym for Highway Addressable Remote Transducer. The HART Protocol makes use of the Bell 202 Frequency Shift Keying (FSK) standard to superimpose digital communication signals at a low level on top of the 4-20mA. Frequency Shift KeyingThe HART communication protocol is based on the Bell 202 telephone communication standard and operates using the frequency shift keying (FSK) principle. The sims 4 life state mods.

The digital signal is made up of two frequencies— 1,200 Hz and 2,200 Hz representing bits 1 and 0, respectively. Sine waves of these two frequencies are superimposed on the direct current (dc) analog signal cables to provide simultaneous analog and digital communications. Because the average value of the FSK signal is always zero, the 4–20 mA analog signal is not affected. The digital communication signal has a response time of approximately 2–3 data updates per second without interrupting the analog signal. A minimum loop impedance of 230 W is required for communication.This enables two-way field communication to take place and makes it possible for additional information beyond just the normal process variable to be communicated to/from a smart field instrument. The HART Protocol communicates at 1200 bps without interrupting the 4-20mA signal and allows a host application (master) to get two or more digital updates per second from a smart field device.

As the digital FSK signal is phase continuous, there is no interference with the 4-20mA signal.HART technology is a master/slave protocol, which means that a smart field (slave) device only speaks when spoken to by a master. The HART Protocol can be used in various modes such as point-to-point or multidrop for communicating information to/from smart field instruments and central control or monitoring systems.HART Communication occurs between two HART-enabled devices, typically a smart field device and a control or monitoring system. Communication occurs using standard instrumentation grade wire and using standard wiring and termination practices.The HART Protocol provides two simultaneous communication channels: the 4-20mA analog signal and a digital signal. The 4-20mA signal communicates the primary measured value (in the case of a field instrument) using the 4-20mA current loop – the fastest and most reliable industry standard. Additional device information is communicated using a digital signal that is superimposed on the analog signal.The digital signal contains information from the device including device status, diagnostics, additional measured or calculated values, etc. Together, the two communication channels provide a low-cost and very robust complete field communication solution that is easy to use and configure.HART NetworksHART devices can operate in one of two network configurations—point-topoint or multidrop.POINT-TO-POINTIn point-to-point mode, the traditional 4–20 mA signal is used to communicate one process variable, while additional process variables, configuration parameters, and other device data are transferred digitally using the HART protocol (Figure 2).

The 4–20 mA analog signal is not affected by the HART signal and can be used for control in the normal way. The HART communication digital signal gives access to secondary variables and other data that can be used for operations, commissioning, maintenance, and diagnostic purposes.The HART Protocol provides for up to two masters (primary and secondary). This allows secondary masters such as handheld communicators to be used without interfering with communications to/from the primary master, i.e. Control/monitoring system.The HART Protocol permits all digital communication with field devices in either point-to-point or multidrop network configurations:Multidrop ConfigurationThere is also an optional “burst” communication mode where a single slave device can continuously broadcast a standard HART reply message.

Higher update rates are possible with this optional burst communication mode and use is normally restricted to point-to-point configuration.The multidrop mode of operation requires only a single pair of wires and, if applicable, safety barriers and an auxiliary power supply for up to 15 field devices. All process values are transmitted digitally. 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). Communication Modes1. Master Slave ModeHART is a master-slave communication protocol, which means that during normal operation, each slave (field device) communication is initiated by a master communication device. Two masters can connect to each HART loop.

The primary master is generally a distributed control system (DCS), programmable logic controller (PLC), or a personal computer (PC). The secondary master can be a handheld terminal or another PC.

Slave devices include transmitters, actuators, and controllers that respond to commands from the primary or secondary master2. Burst ModeSome HART devices support the optional burst communication mode. Burst mode enables faster communication (3–4 data updates per second). In burst mode, the master instructs the slave device to continuously broadcast a standard HART reply message (e.g., the value of the process variable). The master receives the message at the higher rate until it instructs the slave to stop bursting.DEVICE DESCRIPTIONSome HART host applications use device descriptions (DD) to obtain information about the variables and functions contained in a HART field device. The DD includes all of the information needed by a host application to fully communicate with the field device.

HART Device Description Language (DDL) is used to write the DD, that combines all of the information needed by the host application into a single structured file. The DD identifies which common practice commands are supported as well as the format and structure of all device-specific commands.

A DD for a HART field device is roughly equivalent to a printer driver for a computer. DDs eliminate the need for host suppliers to develop and support custom interfaces and drivers.A DD provides a picture of all parameters and functions of a device in a standardized language. HART suppliers have the option of supplying a DD for their HART field product.

If they choose to supply one, the DD will provide information for a DD-enabled host application to read and write data according to each device’s procedures.DD source files for HART devices resemble files written in the C programming language. DD files are submitted to the HCF for registration in the HCF DD Library. Quality checks are performed on each DD submitted to ensure specification compliance, to verify that there are no conflicts with DDs already registered, and to verify operation with standard HART hosts.