Vaisala AQT400, User Manual

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5. Measurements
5.1. Stabilization Period
When AQT400 is switched on, let the unit stabilize for at least 24 hours before using the
measurement results. To ensure optimal measuring accuracy, Vaisala recommends a
stabilization period of 48 hours. The units take measurements during the stabilization
period, but they are marked as invalid.
5.2. Measured Variables
The measured variables have been configured to AQT400 at the factory. When the air
quality transmitter is on, it continuously takes measurements, regardless of how often the
measurements are sent to the database or printed out from the serial port. The
measurements of the particle counter are based on the number of particles sampled over a
period of sixty seconds. You can set the measuring interval to 1 ... 1440 minutes for both gas
and particle measuring.
5.3. Measuring Units
AQT400 reports the gas measurements as parts per million and the particles in µg/m
3
. The
temperature readings are in degrees, Celsius (°C) or Fahrenheit (°F). The air pressure is
represented in mbar. To change the reported units, use AQT Configuration Tool.
5.4. Impact of Ambient Conditions
The ambient conditions (temperature and relative humidity) can influence and distort the
measuring results. AQT400 includes a sophisticated compensation feature for eliminating
the distortion in a non-condensing environment. If the conditions change very fast (for
example, the relative humidity suddenly drops), there may be some measuring inaccuracy
that temporarily exceeds the specifications.
Chapter 5 – Measurements
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