Kestrel 4000 Instruction Manual page 10

Kestrel 4000 Pocket Weather
®
- Ideally, provide an airflow of at least 1 M/S (2.2 MPH), over the temperature sensor—point the
Kestrel Meter into the airflow. If there is no airflow, simply wave the unit back and forth so air
passes over the sensors. With airflow over the temperature sensors and humidity chambers,
readings within specifications will be provided within two to three minutes, even after a large
temperature shift.
- If no airflow can be provided, you must allow sufficient time for the RH value to stabilize. This can
take as long as 20 minutes—the greater the temperature change, the greater the time. You can
use the logging capability of the Kestrel Meter to confirm that the unit has stabilized to
a correct reading: Set the memory options to a relatively short logging interval (20 seconds
works well), select the graphical display of RH, and you can see when the value is no longer
changing significantly. At that point, the RH value is stable and can be relied upon to be within the
accuracy specifications.
Barometric Pressure and Altitude Adjustment
The Kestrel Meter measures "station" pressure—the actual air pressure in the measurement location—and
uses this value to calculate barometric pressure and altitude. Station pressure changes in response to
two things—changes in altitude and changes in the atmosphere. Because the Kestrel Meter is constantly
changing location and altitude, it is important to enter adjustments or "references" when accurate pressure
and altitude readings are needed.
Barometric pressure is station pressure corrected to sea level. In order to make the correction, the Kestrel
Meter needs an accurate reference altitude. Altitude is the height above sea level. In order to correctly
calculate altitude, the unit needs an accurate barometric pressure reference, also known as an "altimeter
setting". Fortunately, you only need to know ONE of these values (current barometric pressure or current
altitude) in order to set your Kestrel Meter up to show accurate readings.
Tracker
®