Why hart protocol

The FieldComm Group owns the HART specifications and provides specification development, training, and product registration services associated with the technology. HART is a bi-directional communication protocol that provides data access between intelligent field instruments and host systems.

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. Communication occurs between two HART-enabled devices, typically a smart field device and a control or monitoring system. Instrumentation grade wiring and standard termination practices assure reliable communication.

With over twenty five years of usage and tens of thousands of installations HART technology is used in countless innovative applications. However, on this case, extra or device specific commands will not be accessed, which can lead to a limited experience.

There are between 35 and 40 standard data items on all registered HART devices. Data can be accessed by any communicator or approved configuration tool. These items do not require a DD and usually include the basic functionality of the device. Accessing device specific data requires a current DD for that particular device as it provides the communicator with the information needed to fully access all of the device's specific features. If equipped, a HART handheld communicator can also make it easier to maintain device configuration records.

The configuration data of the installed device can be stored in memory or on a disk for later archiving or printing. Handheld connections can be made anywhere in the control loop, they do not need to be physically located near the device.

Compared to a handheld communicator, a PC can offer an improved display. It can also support more DDs and device settings because of the additional memory storage capacity. Due to the critical nature of the device settings in the factory environment, PCs can also be used as backup storage for handheld data communicators. Software applications are available from many suppliers. It is important to review its features to determine ease of use, the ability to add or download native FieldComm Group DDs, and general functionality.

Devices equipped with the HART protocol are nowadays widely accepted throughout the industry. The combination of digital communication with the mA signals provides flexibility to transmitters, valve positioners, flow meters and other intelligent devices. In addition to the primary variable monitored, the protocol brings additional information of other variables measured or calculated by the transmitter. Although the digital signal is relatively slow and the loss of functionality of the analog signal in multidrop mode, there are still many advantages to using the HART protocol.

The use of HART multiplexers and the integration with other technologies and protocols can overcome the speed and the restricted number of devices up to 64 devices in multidrop mode. Self-diagnosis is a valuable resource to detect any problems in the plant. The protocol also ensures interoperability between registered HART devices regardless of manufacturer.

This is due to the stringent technical requirements that must be met in the certification process, both the device hardware and the DD. The cabling structure cost is another attraction. In many cases the reuse of the previously installed mA structure takes place.

Another outstanding feature of the protocol is the ability to accurately encode and decode HART communication signals in noisy and hostile industrial environments. The electronics manufacturer, whose headquarters are in the Canoas Innovation Park, was able to circumvent the component shortage and continue growing in and At NOVUS, we consider it essential for relationships to be respectful, which is why the organizational climate is one of the pillars of our strategic planning.

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Product Descr. Similar Search. Type some word. Figure 2: Point-to-point mode In multidrop mode, all HART devices are in parallel and sharing a single transmission line.

The command set includes three classes: Universal: These commands must be recognized and supported by all devices that use the HART protocol. The table below shows some examples of HART commands. 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 W is required for communication.

The HART Protocol communicates at bps without interrupting the mA 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 mA signal. Communication occurs using standard instrumentation grade wire and using standard wiring and termination practices. The mA signal communicates the primary measured value in the case of a field instrument using the mA 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 devices can operate in one of two network configurations—point-topoint or multidrop. In 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 permits all digital communication with field devices in either point-to-point or multidrop network configurations:.

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. Communication Modes. HART 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 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 master.

Some HART devices support the optional burst communication mode. Burst mode enables faster communication 3—4 data updates per second.