Kestrel 3000 - Manual (Page 5)

Kestrel® 3000 Pocket Weather® Meter 9
Replacing the Impeller
You may recalibrate the wind speed readings by replacing
the impeller. Press FIRMLY on the sides of the black impeller
housing with your thumbs to remove the entire assembly.
When inserting the new impeller, be sure the arrow is facing
the display side of the unit, and is aligned with the top of
the meter. Press on the sides of the housing rather than the
center.
Taking Accurate Humidity, Heat Stress and Dewpoint Measurements
The patented system for measuring relative humidity allows for extremely fast and accurate
readings. The sensor is located in the large hole on the rear of the unit. Even extreme and
abrupt changes in the surrounding humidity will be measured within several minutes. To
test this, place your hand around the rear of the unit. Within several seconds, the humidity
will increase dramatically. After removing your hand, the humidity will quickly begin to
decrease. Next, place your hand near the rear of the unit and wave the unit back and forth.
The humidity will not change because the air flow is diluting the humidity from your hand.
This example shows the importance of keeping air flow past the sensor while taking a
measurement. If there is no natural air flow past the sensor, wave the unit back and forth.
It is also reasonable to lay the unit down on a solid surface for several minutes to allow the
sensor to adjust.
Replacing the Impeller
Sensors & Calibration
Kestrel Pocket Weather Meters use precision sensors to measure the environment. These
sensors have all been factory calibrated to NIST-traceable standards, and are accurate within
the stated specifications at the time of manufacture.
The wind is measured with the patented user-replaceable impeller. It is mounted on a
sapphire bearing that begins to measure readings in the slightest of breezes.
The patented external temperature sensor is mounted on long, coiled leads that help
to further isolate the bulb from the case. This ensures that the Kestrel is reading the air
temperature and not the case temperature, may be warmer if the unit was in your pocket or
warmed by your hand.
The patented relative humidity sensor is designed to adjust quickly to abrupt changes in
humidity, and maintains this accuracy and speed in extremely low humidity conditions.
The RH sensor is located on the back of the unit and is protected by a membrane. DO NOT
puncture this membrane. It will damage the sensor and require replacement.
For recalibration of the sensors, the unit may be returned to NK for factory calibration. The
wind and humidity sensors can all also be field-calibrated. To recalibrate the wind speed,
simply replace the impeller. Visit www.nkhome.com for information on the RH field-
calibration kit. The temperature sensor does not need to be recalibrated.