We are continuing our research in Professor Profiri’s Dynamical Systems Lab. We are investigating air quality over the Gowanus Canal. Specifically, we are testing the air for the presence of VOC’s (volatile organic compounds), ozone, and nitrogen dioxide.

The presence of these substances will be detected with air quality sensors. After receiving our newly purchased air quality sensors, we developed an interface circuitry on a breadboard to connect the VOC sensor, nitrogen dioxide sensor, and ozone sensor and to calculate the sensor resistance.

Each of these sensors has four pins. A heating voltage VH was applied across pins 1 and 3. A load resistor RL was connected in series with the sensor resistance RS. The use of RL allows us to relate the voltage VS across pins 2 and 4 to the sensor resistance RS. The given heating voltage values were selected to be 2.35V for the ozone sensor, 1.7V for the nitrogen dioxide sensor, and 2.4V for the VOC sensor.

Using the voltage division formula, we determined the following resistance values for the three sensors 77 Ohms across the ozone sensor, 128 Ohms across the nitrogen dioxide sensor, and 80 Ohms across the VOC sensor.