Page 307 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

passed into the Renaissance, devices for measurement were devised for heat, pressure, and various other parameters in order to support the budding field of scientific investigation.
While the sensor was reactive to changing physical phenomenon a actual metric for measure- ment was ill-defined. The early scientist was burdened to come up with a common and accepted scale by which physical characteristics would be measured (e.g., pressure in pascal/bar/atmosphere/ torr/psi, temperature in Kelvin/Celsius/Fahrenheit/Rankine/Delisle/Newton/Re´aumur/Rømer). In all instances, the scale required a linear relationship (or logarithmic that could be plotted in some lin- ear function) so that the instrument output could scale in a predictable fashion. Regardless of the units used, the end product of sensor functionality is always the same—to measure physical phe- nomena and then convert those measurements into information translatable by humans or other machines for further action.
12.1.2 Function of sensors
For the purposes of this text, the term “sensor” will deal with those mechanisms that sense physical parameters and then turn their measurements into electrical signals (as opposed to simple passive sight systems such as the mercury thermometer or the Bourdon tube, shown in Figure 12.1). A host of sensor technologies can be employed to reach the same conclusion regarding a certain physical
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FIGURE 12.1
Typical bourdon tube pressure gauge.
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