Thermo Scientific 5028i, Инструкция по эксплуатации

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Thermo Fisher Scientific Model 5028
i
Instruction Manual 1-1
Chapter 1
Introduction
The Model 5028i Continuous Particulate Monitor continuously
measures two mass concentration of suspended and refined particulates
(e.g., TSP, PM
10
, PM
2.5
, and PM
1
) simultaneously by the use of beta
attenuation. In addition, the influence of natural Radon (Rn-222) gas
is corrected for as a mass refinement step allowing better sensitivity at
lower ambient particulate concentrations.
In contrast to other beta attenuation monitors using Carbon-14 (C-
14) as a source of the beta rays, the Model 5028 i particulate sample
collection area is located between both the C-14 source and the
proportional counter. While ambient particulate is being deposited
onto a filter tape sample spot, the dynamic filter loading is measured
simultaneously by the attenuation of the C-14 source beta rays. As a
result of this configuration, a continuous real-time measurement of
airborne particulate is provided. It is not necessary to move the filter
spot from the sample position to a separate detector position for zero
and mass determinations (old step-wise method of beta attenuation
monitors). Therefore, uncertainties associated with step-wise filter
transport are eliminated by the use of this continuous ambient
particulate monitoring method.
The Model 5028
i takes into consideration background interferences
with known beta attenuation methods. When present, the daughter
nuclides of the natural noble gas Radon (Rn-222) attach to airborne
particulates, which are then collected on the sample filter during mass
measurement. Some of the radioactive daughter nuclides are also an
emitter of beta rays interfering with the measurement of the particulate
mass. The effect of the interference is generally greatest during:
l
The first 90 minutes after a filter change until the radiological
equilibrium on the filter is reached
l
Periods of rapidly changing Radon gas levels
l
When the activity of the C-14 source is very low