What two sensors can the digital airflow indicating system use?

• A. Pinwheel sensor and RTD sensor
• B. Magnetic sensor and thermocouple
• C. Hall effect sensor and pressure sensor
• D. IR sensor and capacitive sensor

Answer: (A)

Two approaches can power a digital airflow indicating system: a pinwheel sensor and an RTD sensor. The pinwheel sensor uses a small turbine that spins with the moving air; the system counts the pulses from the turbine to determine the airflow rate and displays it digitally. The RTD sensor relies on a resistance temperature detector to sense air temperature (or changes caused by moving air on a known heater element); the resulting resistance change is converted into a signal that indicates air flow. Having these two options lets the system either measure flow directly with a rotating element or infer it from temperature effects, depending on the installation or environmental constraints. Other sensor types listed don’t provide a direct, reliable airflow indication in this type of compact system.