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Automating Manufacturing Systems - Process Control and ...

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continuous sensors - 23.12<br />

on<br />

off<br />

on<br />

off<br />

Figure 23.11<br />

Measuring Motion with Moire Fringes<br />

These are used in high precision applications over long distances, often meters.<br />

They can be purchased from a number of suppliers, but the cost will be high. Typical<br />

applications include Coordinate Measuring Machines (CMMs).<br />

23.2.3.4 - Accelerometers<br />

Accelerometers measure acceleration using a mass suspended on a force sensor, as<br />

shown in Figure 23.12. When the sensor accelerates, the inertial resistance of the mass<br />

will cause the force sensor to deflect. By measuring the deflection the acceleration can be<br />

determined. In this case the mass is cantilevered on the force sensor. A base <strong>and</strong> housing<br />

enclose the sensor. A small mounting stud (a threaded shaft) is used to mount the accelerometer.<br />

Base<br />

Mounting<br />

Stud<br />

Force<br />

Sensor<br />

Mass<br />

Housing<br />

Figure 23.12<br />

A Cross Section of an Accelerometer<br />

Accelerometers are dynamic sensors, typically used for measuring vibrations<br />

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