An industrial optical sensor is used to monitor high-precision manufacturing processes.
Describe the differences between analogue and digital signals. You may draw a diagram to support your answer.
A high-precision laser rangefinder is used in industrial manufacturing to measure the distance to a silicon wafer during fabrication.
A laser light pulse is emitted from a transmitter, travels through a protective gas layer, reflects off the surface of the silicon wafer, and is then received by an optical detector next to the transmitter.
The equation linking average speed, distance moved and time taken is:
average speed=distance movedtime taken \text{average speed} = \frac{\text{distance moved}}{\text{time taken}} average speed=time takendistance movedThe distance between the transmitter and the surface of the silicon wafer is 2.7 mm.
The laser light travels at an average speed of 1.8 × 108 m/s in the protective gas layer.
Calculate the time taken for the laser light to be received at the detector after it is emitted from the transmitter.
A moving-coil geophone is an electromechanical device used by geophysicists to record seismic ground vibrations.
The diagram shows the simplified construction of a geophone.
Explain how the moving-coil geophone produces an electrical signal when a seismic ground vibration occurs.
