1.1 Optical Particle Counter
Aeroqual uses an OEM 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 pulse and the amplitude of the pulse is calibrated
to a particle diameter. The particles are thus assigned on the
basis of size to one of eight channels.
1.1.1 Electrical connections
The connections to the optical particle counter are at the bottom of the unit. There is also a LED which
turns red if there is a fault condition (see Troubleshooting section). The optical unit also requires an
earth wire to be connected between the housing and the 0VDC line on the power bus. Please check
that this is fitted if the unit has been replaced.
1.1.2 Data Outputs
The
Dust Sentry Pro
is configured to display and log particle mass by default. However, there is
also an option to configure the instrument to record particle counts. These can be chosen via the
configuration option in the PC software. Refer to Section 3.1 for more information.
Not used
RS232 serial
LED
Green = Normal
Red = Fault
12 VDC in
Not used
Air out
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.
