HART Protocol - The Preferred Choice for Industrial Field Communication
As a key communication standard in the field of industrial automation, the HART protocol boasts several significant advantages, making it widely used in smart instruments and process control systems. The main advantages of the HART protocol are:
1.Adopt a unified Device Description Language (DDL)
Field device developers use this standard language to describe device characteristics. The HART Foundation is responsible for registering and managing these device descriptions and compiling them into a device description dictionary. The master device uses DDL technology to understand the characteristic parameters of these devices without having to develop dedicated interfaces for them. However, due to this mixed analog-digital signal system, it is difficult to develop a communication interface chip that can meet the requirements of various companies. HART can utilize bus power supply, meet intrinsic safety and explosion-proof requirements, and form a dual-master device system with a handheld programmer and a management system host as the main devices.
2.Bidirectional communication
Using analog signals can only transmit information in one direction, such as from field devices to the control room host (input) or from the control room host to field devices (output). However, using the HART protocol allows for bidirectional transmission of digital information.
This breaks through the traditional way in which instruments can only receive control signals from the control room host computer, such as valve control, and can also transmit information status from the valve to the control room host computer. Similarly, in the past, only process variables could be sent to the monitoring computer, but now information such as configuration settings can also be received.
3.Various types of information
Traditional analog signal and discrete device can only communicate in a single process variable mode, that is, they can only transmit process variables. Therefore, it is difficult to find a simple way to determine whether the sent information is valid.
HART devices can not only acquire process variables but also obtain other types of information. Each HART device includes 35-40 standard information items, such as device status and diagnostic alarms, process variables and measurement units, loop current and percentage range, basic configuration parameters, manufacturer, and device label. Other information includes whether the settings replied by the host when querying the HART device digitally are correct and whether the operation is normal. Such a variety of information helps predict process failures before they lead to major accidents, eliminating most routine maintenance work.
4.Multi-variable instrument
In digital communication mode, a pair of cables can handle multiple variables. For example, a flow transmitter can process inputs from multiple sensors such as differential pressure, pressure, and temperature, that is, it can handle four process variables in a single message.
5.Not subject to suppliers
Since HART technology is not owned by a specific company or controlled by a country or standard entity, but is managed by the unrestricted non-profit HART Communication Foundation, users are not restricted to a particular supplier or local "standard". This allows users to procure HART products from different suppliers and have them work together within the same system. Currently, some of the most widely used HART instruments on the market include: E+H, ABB, YOKOGAWA, Emerson, VEGA, Honeywell, KROHNE, and more.
6.Multi-channel supply
In terms of process industries, HART is currently a widely adopted protocol worldwide. Hundreds of products utilizing HART technology are available from various suppliers. The comprehensive range of product types means that HART products can meet the needs of almost all process applications, and users can choose the most suitable one from multiple distributors' offerings.
7.Interoperability
Full interoperability means that HART-compatible products and host systems from any supplier can work together. To achieve compatibility with HART devices, some host systems use uniformly represented commands, and more advanced systems also use device descriptions to understand all HART information.
Our company specializes in HART protocol signals and has developed a universal HART communication device, SM100-C, which can accommodate all devices or instruments that support HART protocol transmission on the market.
（1）SM100-C (III) HART MODEM and Endress+Hauser Flowmeter Communication Application
（2）Communication application between SM100-C (III) and Fisher 6200 valve positioner
（3）Communication application of SM100-C(III) and EJA differential pressure transmitter
