LED based photoacoustic NO$_2$ sensor with sub-ppb detection limit

An LED based photoacoustic NO$_2$ sensor is demonstrated. A high sensitivity is reached with cantilever-enhanced sensing and a white-light LED. To counteract issues arising from background drifts, the LED spectrum is divided into two channels for a relative measurement. Noise level below 1 ppb is reached with an averaging time of 70 s.