CEL-712 Microdust Pro Real-time Dust Monitor
33 Casella Measurement
Figure 17 Set the Calibration Insert value
3.12 Calibration for specific particulate types - Gravimetric calibration
The measurement sensitivity of the Microdust Pro Microdust Pro instrument
varies according to properties of the particulate that it is measuring, such as the
aerodynamic size, particle shape, material refractive index and colour. This is a
common characteristic of all instruments that use light scattering methods for
measuring particulate concentration.
The Microdust Pro instrument’s use of a narrow forward scattering angle
minimises these effects, but for optimal accuracy when measuring a specific
particulate type, you should perform gravimetric calibration.
Optional gravimetric and respirable adapters incorporate 37 mm filter cassettes
and provide a convenient method of gravimetrically calibrating the instrument.
Refer to section 7.1 Sampling Adapters beginning on page 46 for information
about these adapters.
Standard gravimetric techniques can be used to provide a cross-check between
the instrument’s real-time readings and a weighed example. This is achieved by
collecting two average measurements over the exposure period – one from the
filter (the gravimetric value) and the other from the instrument’s averaging
function. If there are differences between the gravimetric value and the
instrument’s reading, a user-defined correction factor can be entered for the
relevant particulate type. This correction factor can then be applied
automatically to any measured values to provide optimal measurement
accuracy.
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