What does the circuitry of an electronic thermostat recognize?

What does the circuitry of an electronic thermostat recognize?

• A. Changes in resistance as changes in temperature.
• B. Changes in pressure as changes in temperature.
• C. Changes in voltage as changes in current.
• D. Humidity fluctuations.

Answer: (A)

Electronic thermostats detect temperature by measuring a sensor whose resistance changes with temperature. The most common sensor is a thermistor. As temperature changes, the thermistor’s resistance shifts, and the thermostat reads this resistance (usually via a voltage divider and an ADC) to determine the current temperature. The control logic then compares that temperature to the setpoint and activates heating or cooling as needed. Pressure, humidity, or direct voltage/current changes aren’t how the thermostat gauges temperature in its basic sensing circuitry, so changes in resistance as temperature changes is the correct concept.

Electronic thermostats detect temperature by measuring a sensor whose resistance changes with temperature. The most common sensor is a thermistor. As temperature changes, the thermistor’s resistance shifts, and the thermostat reads this resistance (usually via a voltage divider and an ADC) to determine the current temperature. The control logic then compares that temperature to the setpoint and activates heating or cooling as needed. Pressure, humidity, or direct voltage/current changes aren’t how the thermostat gauges temperature in its basic sensing circuitry, so changes in resistance as temperature changes is the correct concept.