PLC Practice Questions

Explain what the following PLC Practice Questions on “ladder-logic” circuit does, and identify the meaning of each symbol in the diagram:

PLC Practice Questions

1. Explain why the TSH uses a normally-open contact instead of a normally-closed contact.
2. Explain why the TSL uses a normally-closed contact instead of a normally-open contact.
3. Based on what we see in this diagram, determine whether the electric solenoid valve allows cooling water to flow when energized, or when de-energized.
4. What do the designations “L1” and “L2” refer to in ladder-logic electrical diagrams?
5. Suppose switch TSL has a trip setting of 105 deg F (falling) and a deadband value of 2 deg F. Explain how this switch will respond to a rising and falling temperature.
6. Suppose we wished to have switch TSHH activate two different alarm lights instead of just one. Modify the circuit diagram accordingly.

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