Airflow Sensor

This airflow sensor consists of INA326 precision instrument amplifier, double 100uA REF200 current sources, and a REF3025 2.5V reference voltage chip. Airflow dynamics dictate how much the voltage will increase or decrease for a given airflow rate. Therefore, the relationship between temperature and flow rate would have to be established for a method such as this to be useable. Two IN4148 diodes are used to sense the temperature, Diode D3 should be in static air and Diode D2 should be installed in the airpath flow path. The circuit works with 5V_DC and draws a few mA of current. REF3025 provides an accurate reference voltage which is 2.5V. Temperature linearity is within a tenth of a degree. The airflow is correlated to the change in D2 voltage. D2’s junction temperature and voltage are related to the airflow. D2 and D3 should be in the same temperature environment.