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Alphasense OPC-N3

Wide-Ranging, Airborne Particulate Sensor

March 24, 2018
New-design optical particle counter adds automatic range-switching capability

ALPHASENSE launched a new version of its OPC-N3 optical particle counter, with all of the advantages of the predecessor model plus automatic range-switching capability covering PM10, PM2.5, and PM1. With an expanded measuring range (0.38 to 40 μm), the OPC-N3 is able to measure the particulate fractions of most interest; from the finest of particles up to larger particles such as pollen. “This is an extremely important development for manufacturers of air-quality monitoring instrumentation,” says Alphasense Director, Arthur Burnley.

Over the past 60 years, developed countries have instituted air-quality standards and regulations to reduce smoke pollution, involving particlates that could be seen by the human eye. Cleaner forms of heating, including electricity and gas, significantly lowered levels of particulate and sulphur dioxide pollution.

Today, the particulate fractions of greatest concern are the finer particles (PM2.5 and now PM1) that cannot be seen by the eye and have to be measured instrumentally. These particles have a major impact on health because they are able to travel deeper into the lungs.

According to the European Commission, in the EU 27 some 500,000 people die prematurely every year, mainly due to exposure to high levels of fine particulate matter (atmospheric microparticles or ‘dust’ of a diameter of less than 2.5 microns) originating from residential heating, transport (diesel cars and trucks, ships and planes), agriculture, industrial processes and power generation.

Several studies have demonstrated that smaller particles appear to be more toxic than larger particles. Research is focused on understanding the surface chemistry of smaller particulates and their toxic effect on health. Arthur says: “The ability of the OPC-N3 to measure across a wide range of particle sizes, and to auto-range, is therefore very important because it means that accuracy and reliability is retained irrespective of the particle size fraction being measured.”

The OPC-N2 was originally developed at the Centre for Atmospheric and Instrumentation Research at the University of Hertfordshire. Over the following five years, the product was refined through a collaboration between the University and Alphasense. The sensor has also been proven in the field, including for example, the capture of more than 150 million readings at London’s Heathrow airport. The OPC-N3 measures particulates accurately, repeatedly, and with minimal maintenance using a patented design, providing both particulate matter readings and real-time particle size histograms. As such, the sensor competes in performance with existing analytical units but at a fraction of the cost.

With the OPC-N3, Alphasense has offers a more rugged design of the OPC-N2, with the same dimensions and power/ interface as the N2. The OPC-N3 now measures from 0.35 μm to 40 μm, sorting into 24 size bins.

Features include improved aerodynamics with reduction of particle deposition; better low-end performance; extended upper size measurements and high/low flow-rate digital selection. The OPC-N3 can measure from clean rooms to pollution levels to 2,000 μg/m3 with the novel feature of being able to size speciate pollen.
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