The thin round quartz plate is gold plated to form electrodes on both sides. The particles are electrostatically deposited in a circular area on one side for mass sensing. When  the electrical signal is exciting, the AT-cut quartz crystal will vibrate in the lateral direction parallel to its surface. The mass of deposited particle will cause the lower resonant frequency of the crystal. The movement of the frequency is proportional to the amount of particles deposited on the crystal, thus providing a signal output for quality monitoring. The QCM is placed in a monitoring chamber maintained at 40℃ to minimize the effect of moisture on the mass of the measured particles.

 The aerosol from the ambient atmosphere enters the system through the weatherproof inlet shown in Fig 2. The aerodynamically equivalent diameter particles larger than 10 m are removed by inertial impact. The inlet is a conventional US EPA blinds designed to operate at a sampling flow rate of 16.7 liters / min.

Half of the total flow into the inlet then flows through the filter sampler shown in Figure 3, which is used for PM10 particle sampling. The sampling flow is 8.33 LPM. The collected particles may be subjected to gravimetric analysis and / or chemical analysis. The filter sampler accepts a standard 47 mm diameter filter. Quartz fiber filters are usually used. Other filters that are compatible with gravimetric and / or chemical analysis techniques may also be used.

The virtual impactor particle separator shown in Figure 4 is used to remove particles larger than 2.5μm for sampling and quality monitoring within the PM2.5 size range. The aerosol is sampled into the inlet nozzle to accelerate the flow rate to the high speed. Particles larger than the aerodynamic equivalent diameter of 2.5 μm are impacted into the receiving tube and transported in small flow form to the outlet for disposal. PM2.5 particles are laterally deflected and carried by the mainstream to the outlet for PM2.5 sampling and quality monitoring. The virtual impactor is designed to work with a 20: 1 overall and small volume flow ratio.
The PM2.5 stream then enters a filter sampler similar to that shown in Fig 3. A small amount of flow is also sampled into the charge and deposition chamber for PM2.5 quality monitoring via QCM.

The chamber shown in Figure 5 is used to charge the particles and deposit on QCM for PM10 or PM2.5 quality monitoring. PM10 or PM2.5 aerosols enter the upper chamber, produce positive corona ions by the high-pressure corona discharge to make the particles charged. Charged particles and then enter the lower chamber, deposit on QCM for quality monitoring. The flow rate through each chamber was 0.5 l / min.
To prevent water vapor condensation on the QCM, the upper and lower chambers of Figure 5 are maintained at elevated temperatures. The conventional room temperature is 40℃.