Research on measurement accuracy by simultaneous counting and differential configuration for quartz crystal smell sensor

Simultaneous counting and drift compensation method is proposed for a simple correction of Quartz crystal (QC) smell sensor that is expected to use in a portable smell measurement device. In general, the frequency of the QC sensor is fluctuated by gate time, noise, temperature and humidity. The frequency fluctuation caused by the supply variation and noise was corrected by time-base QC sensor. The drift caused by temperature and humidity was tried to compensate by reference QC sensor. The frequency measurement resolution was proved by equalizing the slightly fluctuated counting time. The frequency drift was decreased by frequency differential approach between NH₃ QC sensor and reference QC sensor into less than 20%RH for the temperature and humidity variation. NH3 density of 100 ppb could be measured by the smell measurement system.