说明：  HART协议采用基于Bell202标准的FSK频移键控信号，在低频的4-20mA模拟信号上叠加幅度为0.5mA的音频数字信号进行双向数字通讯，数据传输率为
(The HART protocol uses frequency shift keying signal, FSK-based standard Bell202 0.5mA audio digital signal superimposed on the low frequency of 4-20mA analog signal amplitude two-way digital communications, data transfer rate)