As shown in figures "A", "B", "C", "D" and...

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Question 1 of 205eccefa5bacbc34ba4d4869c

As shown in figures "A", "B", "C", "D" and "E" of the illustration pertaining to various diagrams specific to a PLC controlled temperature control system using a thermistor and operational amplifier, which statement is true? See illustration EL-0254.

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🔍 Key Concepts

• Thermistor behavior – does its resistance (and therefore voltage) change in a smooth, continuous way with temperature, or only jump between two fixed values? • Operational amplifier/comparator role – in Fig. B, does the op-amp output swing between two levels once the sensor voltage crosses a reference, or follow the input smoothly? • PLC I/O types – in Fig. C and D, are the PLC input from the op-amp and the output to the heater contactor treated as ON/OFF signals or continuously variable levels?

💭 Think About

• Look at Fig. A: as temperature changes, what happens to the thermistor’s resistance and the ‘output voltage’ point? Would that be considered analog or digital? • Study Fig. B’s little graph: does the op-amp output change gradually with input, or does it suddenly switch from low to high around the reference? What does that tell you about the signal type going into the PLC? • Examine Fig. C, D, and E: the PLC drives a contactor and the ladder diagram shows coils and contacts. Would a contactor/heater coil normally be controlled with a continuously variable voltage or a simple ON/OFF command?

✅ Before You Answer

• Be clear on the definition: analog = continuously variable level, digital/discrete = two (or a few) distinct states such as ON/OFF. • From the diagram, verify what kind of signal leaves the sensor circuit and what kind of signal the heater contactor actually receives. • Match each answer choice to the diagrams: make sure both the input (from thermistor/amp) and the output (to heater/contactor) match what the figures show about being analog vs digital.

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