An intrinsically safe electrical tomography system

In recent years industrial tomography has emerged as a valuable tool for interrogating the internals of a variety of process vessels. A popular approach is to inject electrical current and then from measurements of the resulting boundary voltages to reconstruct a cross-sectional image representing the distribution of materials in the vessel. In many cases the process takes place in a hazardous environment and consequently there is a need for certified safe equipment. This paper reports on the design, construction and testing of the worlds first intrinsically safe electrical tomography system. To achieve certification zener barrier diodes and intrinsically safe relay- modules provide electrical isolation from the hazardous environment. The instrument is certified for operation in a zone O environment and has been operating successfully on a production pressure filter for 2 years.