ABSTRACT
Inductive sensors are designed based on the operating principle and characteristics of an inductor. They are primarily used to measure electric and magnetic fields, or other physical quantities (e.g., displacement and pressure) that can be transformed into an electric or magnetic response. Inductive sensors do not require physical contact; thus, they are noncontact sensors and are particularly useful for applications which access presents challenges. Inductive sensors can only detect metals. They react differently to different metallic materials such as steel, copper, and aluminum. Thus, they can be used to identify different metals. Unlike capacitive sensors, inductive sensors are not affected by nonmetallic media materials between the probe and the target, so they are well adapted to harsh environments where oil, dust, dirt, or other substances are present. The key advantages of inductive sensors include
• Nearly infinite resolution • Fast response • Large operating temperature range • High reliability • Robustness • Easy handling
There are historical examples of various inductive sensors. The ChattockRogowski coil was first described in 1887 [1,2]. Today, this sensor has been redesigned as an excellent current transducer and is used in measuring magnetic properties of soft magnetic materials. An Austrian patent in 1957 described the use of a needle sensor for investigating local flux density in steel [3].
