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低成本粒子探测器

的范围内和紧凑超小型传感器已被开发用于环境监测粒子。根据许可 Alphasense 现在这些设备被制造为 OPC-N2 units. With 16 size bins between 0.38µm and 17µm it can measure up to 10,000 particles per second, either saving data to an on-board microsd card or connected via SPI or USB.

Independent comparison with industry standard instruments carried out at the University of Manchester shows good agreement.

OPC Comparison

This, combined with the low cost and the flexible communication protocols makes it ideal for large scale networks. The technology has been used by the University of Cambridge around Heathrow airport, for detecting volcanic ash 埃亚菲亚德拉冰盖火山喷发期间,上 球载无线电探空仪 在科威特以及最近为部分 AirSensa 整个伦敦网络。

The AirSensa project is creating a UK-wide network of urban air quality monitors that include OPC-N2 technology. They are starting in Greater London, to monitor and visualise air quality right down to individual street level.  Up to 10,000 sensors are to be placed in schools, public and commercial buildings to monitor and feed back data to the cloud where it will be made available online and via smart-phone apps.

研究背景

low cost particle detectors

CACP's interest in low-cost modules for counting and sizing micrometre-sized airborne particles began in 2009 with the DREAME project, funded by NERC (Natural Environment Research Council, NE/G007268/1).

DREAME (Dust Radiation Electrification and Alignment in the Middle East) was led by CACP's Joseph Ulanowski in collaboration with the University of Reading and involved a study of Saharan dust clouds.

These clouds can spread over vast areas as they move out over the Atlantic ocean and can have a significant effect on climate by their interaction with sunlight.

DREAME involve both aircraft and balloon-borne (radiosonde) measurements and, since the chances of recovery after balloon launch were small, the latter required the rapid development of small aerosol optical particle counters (OPCs) that were cheap enough to be 'one-shot' devices.

CACP's Particle Instruments group therefore undertook this development and produced batches of very cheap OPCs that were capable of counting up to ~10,000 particles per second and sorting them into five size bins covering the range 1µm – 16 µm

Volcanic ash probes

准备一个气球发射

Sonde Graph Data

其气球上升超过科威特期间由粒子传感器中的一个产生的气溶胶尺寸数据的一个例子。

Figure 1 Dust Cloud

火山灰检测

An unforeseen application for the low-cost  optical particle counters arrived following the eruption in April 2010 of the Eyjafjallajökull volcano in Iceland.

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The UK Met Office therefore commissioned from CACP further batches of the low-cost particle sensors that could be assembled with radio transmitters and launched by balloon to try to detect the presence of ash in the upper atmosphere.

These completed radiosondes were subsequently launched from various locations and provided the data (see example below) that proved the presence and high density of the ash layer.

This type of data not only fully justified the grounding of commercial flights but also allowed verification of the Met Office's theoretical predictions of how the ash cloud would spread across Europe.

: An example of the detection of the Icelandic volcanic ash cloud by CAIR's low cost OPCs.  Measurement taken in April 2010.

An example of the detection of the Icelandic volcanic ash cloud by CACP's low cost OPCs. Measurement taken in April 2010.

传感器网络的空气质量(snaq)在希思罗机场

A further development of CACP's low-cost particle detection technology came in 2011 with the commencement of the NERC project 'High density sensor network system for air quality studies at Heathrow airport' (NE/I007296/1; visit http://www.snaq.org/ ).

This project, led by Cambridge University, sought to deploy a large network (60+) of so-called 'SNAQ' sensor modules around Heathrow airport in order to acquire detailed information on the spatial and temporal behaviour of airborne pollutants.

The modules already had advanced detectors for various  gases including NO, NO2, CO, O3, CO2, hydrocarbons, and SO2, but also wanted the ability to continuously measure aerosol concentrations over long periods.  CACP's role therefore was to design and produce these low-cost aerosol spectrometers, and subsequently assist analysis of the data they produced.

Unlike the DREAME particle counters above, the particle counters produced for the SNAQ modules employed a novel design which obviated the need for an air-pump and associated particle filters.

Instead, an 'open-path' design based around custom fabricated elliptical mirrors and dual-element photodiode detectors allow simple and robust particle detectors to be produced.

The SNAQ particle detectors have been designed to run continuously for several months, reporting aerosol concentrations to the network host computer over 200 ms intervals several times each minute.

的数据是在16块大小直方图覆盖的尺寸范围0.38-17μm,如在下面的例子中的形式。

SNAQ particle detector

在生产过程中snaq粒子检测器模块。

Example of ambient aerosol size distribution as measured over 200ms by one of the SNAQ Heathrow OPCs designed and built by CAIR.

Example of ambient aerosol size distribution as measured over 200ms by one of the SNAQ Heathrow OPCs designed and built by CACP.

在snaq希思罗机场的测量将持续到2012年和2013年初,其次是详细的分析和报告。