Page 306 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

298 CHAPTER 12 Sensor Theory
12.3.5 Science...............................................................................................................325
12.3.6 Structural inspection ............................................................................................ 326
12.4 The future...................................................................................................................................326
Since the turn of the new millennium, huge leaps forward in sensor technology have been achieved across the realms of science and industry. From the early days of the simple mercury thermometer to the later evolution of the Bourdon tube to the modern macro and nanoscale sensors of the new century, they have been used to sense physical phenomenon and convert related measurements into information discernible by humans or other machines for further action.
Sensors are everywhere in our lives. In our homes, temperature sensor circuits direct feedback to elements that control our heating
cooling systems as well as cooking appliances, optical and pressure sensors are used in our home security systems, acoustic sensors for our phones, voltage/ current sensors for electrical safety, and a host of others. In our cars, wheel turn counters (with use of various technologies) clock our vehicle’s speed (and the police use optical and radio frequency sensors to clock our speed as well . . .), optical sensors turn on/off headlights, pressure/temperature/ fluid level/tachometer/etc. sense engine operating parameters. Boats, power plants, airplanes, space vehicles—and especially underwater vehicles—make extensive use of sensor technology for opera- tion of the machinery we use every day in the modern world.
Sensor technology is a broad and diverse body of knowledge that is rapidly advancing in both scope and depth. An overview of sensor technology elements is provided below. For a more in-depth coverage of the subject, a recommended text on basic sensor technology is the Sensor Technology Handbook by Jon S. Wilson (published in 2005—also by Elsevier).
The purpose of this chapter is to acquaint the reader with the basics of sensor theory in order to better understand the specifications of sensor packages deployed on ROV systems.
12.1 Theory 12.1.1 History
“If real is what you can feel, smell, taste and see, then ‘real’ is simply electrical signals interpreted by your brain” (Morpheus, quoted from the 1999 movie, The Matrix).
Sensor technology is pervasive in the biological world. But similar sensors are tuned to different sensitivity levels as well as differing physical phenomenon in order to achieve the measurement objective. As an example, typical human auditory sensitivity is at a frequency level from 20 Hz to 20,000 Hz while dogs can hear up to 60,000 Hz—and bats up to 150,000 Hz. This is a case of the same sensor being tuned to differing sensitivity and amplitude/source levels for various applica- tions. The reason is the sensors are used for different purposes—humans for voice recognition/ speech dissemination, dogs for identifying prey, and bats for echolocation.
The first mechanical sensors originated with the ancient Greeks. Archimedes designed a specific gravity sensor, a crude odometer, and various other early measurement devices. As civilization