AirTest PT9250 Manuale di applicazione - Pagina 3

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The Display
When the sensor is powered up for the first time
CO
concentrations will appear on the upper
2
screen. The lower screen will alternate between
a display of the temperature in ºF or ºC, and the
cubic feet per minute (cfm) per person of outside
air delivered to the space. CO
used to determine fresh air ventilation rates in the
space.
Battery power level is also displayed in the
middle left portion of the display. Three small
bars indicate a full charge.
The LED's underneath the display provide a
quick check of the concentration.
By using the provided PC interface software and
cable you have the ability to customize how
information is to be displayed by the digital
display and LED's.
Upper Display: CO
Reading
2
Carbon dioxide concentrations are displayed in
parts per million (ppm). The PT 9250 will display
concentrations up to 9,999 ppm . Typical outside
levels are 380 to 450 ppm. Typical inside levels
can vary from 400 ppm to as high as 3,000 ppm.
Lower Display: Temperature & Ventilation
Rate
The lower display alternates between displaying
temperature and providing a calculated value of
the cfm/person ventilation rate in the space. By
using the pC program provided with the sensor
you can change both the location and the way
this information is displayed on the screen.
AirTest PT9250 & CO
Application Guide
2
levels can be
2

3. Spot Check Ventilation Rates

Background
The PT9250 not only measures CO
Temperature but it also calculates the outside air
ventilation rate in cfm per person based on the
difference between inside and outside CO
levels.
So how can we determine the cfm per person
ventilation rate from CO
2
is based on a widely recognized engineering
principal. People will produce almost identical
amounts of CO
when at the same level of
2
exertion or activity (e.g. office work).
indoor CO
measurement indicates how much
2
outside air (at low CO
2
introduced to dilute or remove the CO
produced by people in the space. Regardless of
whether there is one or a hundred people in the
space, the CO
level will reflect how much
2
outside air is being delivered for each person.
This is because the calculation of ventilation rate
is based on the
known amount of
CO
produced by
2
each person and the
known quantity of
outside air that is
required to dilute
concentrations to a
particular level of
CO
. The adjacent
2
chart shows this
relationship between
CO
and ventilation
2
rate.
This would
apply for a typical
office space
and
outside
air CO
2
concentrations
of
400 ppm.
In effect,
this chart is built into
the PT9250.
and
2
2
levels? This calculation
So an
concentrations) is being
being
2
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