Thermo Scientific 5030i SHARP, Инструкция по эксплуатации

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Introduction
Principle of Operation
Thermo Fisher Scientific Model 5030 i SHARP Instruction Manual 1-7
events, a rear-panel mounted zeroing solenoid is activated and HEPA-
filtered air is delivered to the nehpelometer, whereby each range is zeroed.
The results of the zeroing are available via display and C-Link read
commands.
At the location where the nephelometer attaches to the 5030 i instrument
case, a radial insulated tube joins the sampling tube to the collection
chamber. The particulate is drawn onto the glass fiber filter tape between
the proportional detector and the
14 C beta source. Here, the beta beam
passes upwards through the filter tape and accumulated particulate layer.
The intensity of the beta beam is attenuated with the increasing mass load
resulting in a reduced beta intensity measured by the proportional detector.
From a continuously integrated count rate the mass on the filter tape is
calculated. During sampling, the mass on the filter spot is always known
and the rate of particulate accumulation is observed.
A continuous measurement of the flow rate determines the sample volume.
A proportional valve is used to maintain the sample flow rate at its nominal
value. From both integrated sample volume and mass detection the
particulate concentration is calculated. At any given time the output signal
delivers the concentration of particulate in actual or standard conditions.
The Model 5030 i outputs particulate matter concentrations to the front
panel display as SHARP, PM, and NEPH, which are the hybrid, beta
attenuation and nephelometer derived particulate concentrations,
respectively. Displayed concentrations, analog outputs, also makes the data
available over the serial or Ethernet connection.
Additionally, the Model 5030 i proportional radiation detector is sensitive
to natural alpha activity of the aerosol passing through the sampling
system. The additional alpha count rate is used to measure the presence of
Radon gas and infer the daughter nuclides of Radon gas. These daughter
nuclides create a small beta emission. This externally sampled beta emission
is perceived by the detector to be a higher count rate and the higher the
count rate, the less apparent mass detected. Therefore, by measuring the
natural alpha activity due to Radon gas, the proportional beta interference
from the daughter nuclide emissions are subtracted from the count rate to
provide a refined mass measurement. This potential error from Radon gas
interference may be (in lower strength radioactive devices; e.g.; <100 μCi)
as high as actual particle concentrations, especially after filter change or
when the natural activity concentration changes. The Model 5030
i has
implemented this procedure to determine separately the natural activity in
the aerosol and to eliminate this error. This procedure further allows the
Model 5030
i to provide a more stable reading at lower ambient particulate
concentrations compared to similar methods. Furthermore, from this
information the activity concentration of the natural noble gas Radon is
derived.