Abstract

The HART^TM (Highway Addressable Remote Transducer) fieldbus standard has been in existence since the late 1980s. It is a bidirectional communication protocol that provides data access between intelligent field instruments and host systems. It is administrated by the HART Communication Foundation (HCF), located in Austin, Texas [6]. In its initial release, the HART field communication protocol was superimposed on a 4–20 mA signal providing two-way digital communications with smart field instruments without compromising the integrity of the measured data. As shown in Figure 8.1, the HART protocol has evolved from a 4 to 20-mA-based protocol to the current wired and wireless-based technology with extensive features supporting security, unsolicited data transfers, event notifications, block mode transfers, and advanced diagnostics. Diagnostics now include information about the device, the equipment the device is attached to, and in some cases the actual process being monitored.