How to read the real-time data of the hart flowmeter to the upper computer

2025-11-28

HART(Highway Addressable Remote Transducer), an open communication protocol for high-speed channels of addressable remote sensors, was launched by the American ROSEMOUNT Company in 1985. It is a communication protocol used between field intelligent instruments and control room equipment. HART devices offer communication with relatively low bandwidth and moderate response time. After more than 10 years of development, HART technology has become highly mature abroad and has become the industrial standard for global intelligent instruments. HART communication adopts a half-duplex communication mode. Its characteristic is to achieve digital signal communication on the existing analog signal transmission line. It is a transitional product in the process of transforming from analog systems to digital systems. Therefore, it has strong market competitiveness and has developed rapidly during the current transitional period.

Project Background：

A certain sewage treatment plant needs to monitor the real-time flow and cumulative flow of the flowmeter at the discharge outlet in real time. As the flowmeter at the discharge outlet is about 1 kilometer away from the PLC for data collection, a 4-20mA signal is used, but the real-time flow still fluctuates due to interference. The traditional cumulative flow is calculated by the contact signals of the flowmeter, with each pulse measuring 1 cubic meter of water volume. However, due to the accumulation over time, the PLC has a relatively large error in calculating the cumulative flow, and it needs to be corrected monthly, which is rather time-consuming and labor-intensive. Based on the above two points, if you want to read the instrument data in real time through communication, due to the long distance, 485 communication will be unstable. Therefore, the HART protocol is the first choice to be considered

Operation steps：

Since the on-site PLC is not equipped with a 485 port, this communication adopts the HART to Ethernet conversion method.

SM100-TCP intelligent converter is a high-tech product integrating HART protocol and TCP/IP communication. It is a micro RTU system. It is composed of high precision operational amplifier, interface chip, watchdog circuit, input and output circuit, and embedded TCP/IP gateway module and Hart modem chip. It has the characteristics of stable performance and high cost performance.

With just a few simple Settings on the configuration software, data testing can be conducted through the MODBUS testing software.

Through real-time hart communication, the real-time data of the instrument can be communicated. By looking up the table, we canobtain:

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