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Aeroqual AQM60 User Guide
5.
Third Party Sensors
5.1. Particle Monitor
The particle monitor is an optional device that can be installed in the AQM60 to provide reliable real time
indicative particulate measurement of TSP, PM10, PM2.5 or PM1 using a well proven near forward light
scattering nephelometer and high precision sharp cut cyclone.
5.1.1. Nephelometer
Aeroqual uses a nephelometer optical sensor from Met One Instruments. The optical sensor uses light
scattering from particulate matter to provide a continuous real-time measurement of airborne particle mass.
The light source is a visible laser diode and scattered light is measured in the near forward angle using a
focusing optics and a photo diode.
The sensor has an on-board temperature sensor which is corrected for thermal drift, sheath air filter to keep
the optics clean, automatic baseline drift correction and a fibre optic span system to provide a check of the
optical components.
The electrical connections to the nephelometer are summarised below:
Wire colour
Function
Orange (x2)
Fibre optic solenoid
Red
5V (power in)
Black
Ground
White
Signal out (0-5 V)
Black/white
Signal Ground
Yellow
Laser current monitor ( 10mV = 1 mA laser current)
Grey
Temperature output
5.1.2. Inlet heater
The nephelometer uses a 12 V heater on the sample inlet tube to reduce the humidity of sampled air to
prevent particle growth and fogging of the nephelometer optics in high RH conditions.
5.1.3. Inbuilt filters
The nephelometer contains two filters which should be replaced at specified intervals
. The “Sample” filter is a
coarse filter designed to protect the sample pump from excessive particle build-
up. The “Purge” filter is a fine
filter which filters the sheath air flow and also produces particle-free air during the auto-zero cycle.
5.2. Profiler
5.2.1. Optical Particle Counter
Aeroqual uses an optical particle counter from Met One Instruments. The particle counter uses scattered
light to measure and count particles. Light from a laser diode is collimated to illuminate the aerosol sample
flow. When a particle is present it scatters the incident laser light which is detected using a 60
o
solid angle
elliptical mirror at right angles to the laser beam. The amount of scattered light is converted to a voltage
Safety: This sensor is considered a Class I laser product. Class I laser products are not
considered to be hazardous. There are no user serviceable parts inside the cover of the
sensor. The device contains a laser operating at 670 nm which is visible to the eye and can
cause damage to the eye if directly exposed. Only trained service personnel should
attempt servicing or repair of the sensor.
Summary of Contents for AQM60
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