Abstract
A low-noise aerosol electrometer with a wide dynamic range has been designed for measuring the total net charge on high concentration aerosol particles within the range of −500 pA to +500 pA. The performance of the aerosol electrometer was evaluated by a series of experiments to determine linearity, sensitivity and noise. The relative errors were controlled within 5.0%, 1.0% and 0.3% at the range of −40 pA to +40 pA, ±40 pA to ±100 pA, and ±100 pA to ±500 pA respectively. The stability of the designed aerosol electrometer was found to be highly sensitive to temperature variations, but under temperature control, the root mean square noise and the peak-to-peak noise were 1.040 fA and 5.2 fA respectively, which are very close to the calculated theoretical limit of the current noise. The excellent correlation and the advantage of a wide dynamic range have been demonstrated by comparing with the designed aerosol electrometer to a commercial aerosol electrometer. A 99.7% (R2) statistical correlation was obtained; meanwhile, the designed aerosol electrometer operated well even when an overrange phenomenon appeared in the commercial aerosol electrometer.
Highlights
Sensors for aerosol measurement make a important role in aerosol science and technology as well as atmospheric pollution monitor
Aerosol electrometers have been used to measure the charge on charged particles as well as determining the size distribution of particles when the aerosol electrometer is combined with a differential mobility analyzer (DMA) [8,9,10,11]
The triboelectric, piezoelectric, and stored charge effects are caused by vibration and the resultant generated current adds to the desired current, causing errors. (II) Electromagnetic interference (EMI) and radio-frequency interference (RFI) from an external source were prevented by incorporating a Faraday housing with a grounded shielding cover made of aluminum. (III) Instead of long-distance wire transmission, the ultra-low current was amplified and converted to digital signal in one, well shielded circuit. (IV) Teflon insulation was used to eliminate noise due to leakage current
Summary
Sensors for aerosol measurement make a important role in aerosol science and technology as well as atmospheric pollution monitor. Aerosol electrometers have been used to measure the charge on charged particles as well as determining the size distribution of particles when the aerosol electrometer is combined with a differential mobility analyzer (DMA) [8,9,10,11]. Aerosol electrometers have been used to measure and sample atmospheric ions and charged aerosols directly [12,13,14], as opposed to other applications that focus more on the total number concentration of particles than on the size distribution [15]. Some applications have been put forward new demands for aerosol electrometer, which require a wide dynamic range. In-cloud charge measurements require a wide dynamic range, extending from charge in aerosols and dusts to that present in thunderstorms [16]
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