The five senses - vision, hearing, smell, taste, and touch - are universally recognized as the means by which humans and most animals perceive their universe. They do so through optical sensing (vision), acoustic sensing (hearing), chemical sensing (smell and taste), and mechanical (or tactile) sensing (touch). But humans, animals, and even lower level organisms rely on many other sensors as well as on actuators. Most organisms can sense heat and estimate temperature, can sense pain, and can locate a sensation on and in the body. Any stimulus on the body can be precisely located. Touching of a single hair on the body of an animal is immediately located exactly through the kinesthetic sense. If an organ is affected, the brain knows exactly where it occurred. Organisms can sense pressure and have a mechanism for balance (the inner ear in humans). Some animals such as bats can echolocate using ultrasound, while others, including humans, make use of binaural hearing to locate sounds. Still others, such as sharks and fish (as well rays and the platypus), sense variations in electric fields for location and hunting. Birds and some other animals can detect magnetic fields and use these for orientation and navigation. Pressure is one of the main mechanisms fish use to detect motion and prey in the water, and vibration sensing is critical to a spider's ability to hunt. Bees use polarized light to orient themselves, as do some species of fish. And these represent only a small selection of the sensing mechanisms used by organisms.

Chapter Contents:

• 1.1 Introduction
• 1.2 A Short Historical Note
• 1.3 Definitions
• 1.4 Classification of Sensors and Actuators
• 1.5 General Requirements for Interfacing
• 1.6 Units
• 1.6.1 Base SI Units
• 1.6.2 Derived Units
• 1.6.3 Supplementary Units
• 1.6.4 Customary Units
• 1.6.5 Prefixes
• 1.6.6 Other Units and Measures
• 1.6.6.1 Units of Information
• 1.6.6.2 The Decibel (dB) and Its Use
• 1.7 Problems

Inspec keywords: vision; chemioception; chemical sensors; motion estimation; acoustic devices; touch (physiological); electromagnetic fields; brain; tactile sensors; optical sensors

Other keywords: brain; touch; motion detection; binaural hearing; chemical sensor; hearing; electric fields; bees; sense variations; taste; optical sensor; light polarization; prey; kinesthetic sense; magnetic field detection; sensing mechanisms; smell; mechanical sensor; vibration sensing; vision; acoustic sensor; lower level organisms

Subjects: Sensing devices and transducers; Acoustical measurements and instrumentation; Sonic and ultrasonic equipment; Mechano- and chemio-ceptions; Sensing and detecting devices