Principles and Applications of Ubiquitous Sensing

Chapter 4Electrical Sensing

Traditionally, a transducer is the basic element that transforms one form of energy to another form of energy. When this transducer integrates additional elements such as a conditioning circuit, the entire assembly is called a sensor. The term sensing refers to the spectrum of interaction between the measurand and the transducer or the sensing element. Regardless of the nature of the measurand:

• if its initial effect upon the sensing element is modifying the electrical characteristic of the sensing element, we call this interaction an electrical sensing
• if it is modifying the quantum characteristics of the sensing element (that is, if the measurand in some way interacts with quantum level particles such as photons and individual electrons), we call this interaction collectively optical sensing
• if the interaction modifies the magnetic properties of the sensing element, then the interaction is referred to as magnetic sensing.

In most cases, it is possible to determine the type of sensing by referring to the energy the measurand releases. For example, if the measurand releases ultrasonic energy, then this energy can be picked up by an ultrasonic sensor. Therefore, we can refer to the sensing type as an ultrasonic or ultrasound sensing. But there are situations where the nature of the measurand may not correspond with the sensing type. For example, a mechanical force or pressure may modify the electrical, optical, or magnetic characteristics of a sensing ...