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
- Explain why the TSH uses a normally-open contact instead of a normally-closed contact.
- Explain why the TSL uses a normally-closed contact instead of a normally-open contact.
- 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.
- What do the designations “L1” and “L2” refer to in ladder-logic electrical diagrams?
- 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.
- Suppose we wished to have switch TSHH activate two different alarm lights instead of just one. Modify the circuit diagram accordingly.