Some questions about the HART protocol

The HART protocol adds a digital signal on top of the 4-20mA analog signal; it is a transitional protocol. The future development direction of smart meters is definitely towards fully digital systems. The Hart protocol, by incorporating digital signals, enables the transmission of more information to the control system, such as diagnostic data related to the meter, its measurement range, and parameter settings.

HART (Highway Addressable Remote Transducer) is an open communication protocol for addressable remote sensors; it was developed by the American company Rosement in 1985 as a communication protocol used between field smart instruments and equipment in control rooms. After more than 10 years of development, HART technology has become highly mature abroad and has emerged as the industry standard for smart instruments worldwide. However, as far as I know, in the early stages of developing smart instruments, HART was not yet a global standard; therefore, each company developed its own protocols. It was only after HART became a universal industrial standard that many companies began to adopt it. As a result, ROSEMOUNT’s 375 can operate devices such as Fuji’s FCX series, and for this to be possible, there must be some support files specific to Fuji’s technology; the same is true for products developed by other companies that comply with HART standards. Therefore, other devices such as Fuji’s FXW and Yokogawa’s BT200 are unable to communicate with ROSEMOUNT’s intelligent instrument 3051. For the Yokogawa instruments in our company, only BT200 can be used, as HART375 has not been upgraded and cannot be used for communication with them. And the ROSEMOUNT 3051 can only use HART 375 as well.

Going back to the third floor, tqg8888 – the claim that “Yokogawa instruments can only use BT200 because HART375 has not been upgraded” isn’t quite correct. Some Yokogawa instruments use the BRAIN protocol, which is different from HART and therefore not compatible with it.

The statement regarding the third floor is indeed inaccurate. Yokogawa’s transmitters can use either the HART protocol or the BRAIN protocol; when using the HART protocol, Yokogawa has to pay certain patent fees, but since the BRAIN protocol is its own proprietary technology, no such fees are required. If the user does not specify otherwise, Yokogawa will provide smart transmitters that use the BRAIN protocol. Similarly, Honeywell’s transmitters use the DE protocol only if it is required. The 375 upgrade mainly adds support for some newly developed instruments and improves certain functions. During the current transition period, instruments using the HART protocol still predominate.