Digital air flow detection in a duct

An airflow detector, comprising:

• a probe assembly, comprising:
• a cover;
• a probe circuit board residing within the cover;
• an external thermistor coupled to the probe circuit board and residing outside of the cover;
• an insulated thermistor coupled to the probe circuit board and residing within the cover;
• and
• a printed circuit board assembly coupled to the probe assembly and comprising one or more microcontroller units configured to:
• obtain a first temperature from the external thermistor and a second temperature from the insulated thermistor;
• calculate a temperature difference between the first temperature and the second temperature;
• determine whether the temperature difference indicates that air is flowing;
• and
• when the temperature difference indicates that air is flowing, output an indication, wherein the first temperature is converted to a first voltage, and the second temperature is converted to a second voltage, wherein the one or more microcontroller units receive a voltage difference (V) between the first voltage and the second voltage as an input, wherein in calculating the temperature difference between the first temperature and the second temperature, the one or more microcontroller units are further configured to:
• calculate an average differential voltage (dV/dt) over a time interval;
• compare the dV/dt with an on threshold parameter value, the on threshold parameter value setting a minimum value of dV/dt for an indication of air flow;
• determine a state of an air flow flag parameter, wherein an ‘on’ state of the air flow flag parameter indicates that air is flowing, wherein an ‘off’ state of the airflow flag parameter indicates that air is not flowing;
• and
• when the dV/dt exceeds the on threshold parameter value and the state of the air flow flag parameter is ‘off’, set the state of the airflow flag parameter to ‘on’.