The simplest way to measure the photo signal is to take an ADC sample of the buffered AMUX output when the photo chamber LED is enabled. The output level is proportional to the concentration of smoke and one ADC sample is theoretically sufficient to determine the smoke concentration. However, because of variations in offset voltages and leakage currents, the base DC voltage of the photo signal varies from part to part. Additionally, taking multiple ADC samples reduces the measurement noise. It is recommended to take two groups of ADC samples: one group before the LED is enabled to measure the pulse base voltage and one group after the LED is enabled to measure the pulse top voltage. Processing the two groups of ADC samples cancels the baseline DC voltage and the retains the signal amplitude.