This set of Pulp and Paper Multiple Choice Questions and Answers (MCQs) focuses on “Mechanical Sensors”.
1. __________ sensors are utilised to measure variables such as point, velocity, acceleration, force, press, levels and flow.
Explanation: Mechanical sensor is an object whose function is to detect changes in its environment, and then provide a corresponding output. It’s a type of transducer; sensors might provide various types of output, but typically utilize electrical or optical signals.
2. __________ sensors rely on a change of capacitance, resistance, inductance, or reluctance.
Explanation: A point sensor is any device that permits point measurement. It could either be an absolute point sensor or a relative one (displacement sensor). Point sensors could be linear, angular, or multi-axis.
3. A potentiometric displacement sensor utilizes a wire of high resistance with a wiper in electrical contact with the wire.
Explanation: As the object moves across the wire, the resistance of the circuit changes. By measuring the resistance, the point of the object along the wire is known.
4. Variable inductance is achieved by the utilization of __________ core in the shape of a rod which is wraped by a hollow coil of wire.
Explanation: As the ferromagnetic core enters the coil the inductance of the coil is replaced. With reluctance sensors, the magnetic flux coupling b/w 2 or more coils is varied by a ferromagnetic core. Inductance is a calculation that relates electrical flux to the current.
5. __________ sensors is a type of transformer and are the basis of the prevalent L.V.D.T . The signal is easily conditioned to give out a D.C. voltage that in linearly proportional to point over part of the range of motion of the core.
Explanation: It’s a type of sensor that are the basis of the prevalent L.V.D.T. linear variable differential transformer. The sensitivity could be on the order of 0.001 mm movement.
6. __________ could be utilized as a point sensor by measuring a time pulse of __________ takes to echo back to the transmitter. It is similar in principle to a radar.
c) X- ray
Explanation: Ultrasounds are sound waves with frequencies which are greater than the upper audible limit of human hearing. Ultrasound is no different from ‘normal’ (audible) sound in its physical properties, except in that humans couldn’t hear it. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.
7. The __________ factor is the relative change in resistance divided by relative change in length i.e., the definition of strain.
Explanation: Strain gauge is the ratio of relative change in electrical resistance R, to the mechanical strain ε. Metal strain gauges have a gauge factor of about 2; thus a strain of 0.1% would cautilise a 0.24 Ω change in a 120 Ω strain gauge.
8. If a fluid is at rest, one refers to static _________ If a fluid is in motion, one refers to dynamic _________ which is a function of the motion of the fluid.
b) Gravitational force
Explanation: The force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the pressure relative to the ambient pressure
9. Strain ___________ could be mounted on diaphragms to measure pressure; this method has been miniaturized onto integrated circuits.
Explanation: The most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The gauge is attached to the object by a suitable adhesive, such as cyanoacrylate.
10. The temperature of a heated metal filament depends on the gas pressure since the gas molecules could conduct heat from the filament.
Explanation: Very less pressure i.e., very high vacuums, which signifies a gas phase, requiring specialized techniques. Pressure below 10-3 could be measured with ionization gauges.
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