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12.5 PRACTICE PROBLEMS
1. Given a clear plastic bottle, list 3 different types of sensors that could be used to detect it.
2. Why is a sinking output on a sensor not like a normal switch?
ans. the sinking output will pass only DC in a single direction, whereas a switch can pass AC and DC.
3. Select a sensor to pick up a transparent plastic bottle from a manufacturer. Copy or print the specifications, and then draw a wiring diagram that shows how it will be wired to an appropriate PLC input card.
4. a) Sketch the connections needed for the PLC inputs and outputs below. The outputs include a 24Vdc light and a 120Vac light. The inputs are from 2 NO push buttons, and also from an optical sensor that has both PNP and NPN outputs.
b) State why you used either the NPN or PNP output on the sensor.
5. List 3 significant trade-offs between inductive, capacitive and photooptic sensors.
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