The Kestrel impeller IS balanced, and to a very high degree. It APPEARS to be imbalanced because of the tiny magnet incased within the impeller. The force acting on your impeller blade is magnetic, not gravitational. If you want to test this out, simply hold your Kestrel horizontally, and then rotate the entire instrument in the horizontal plane. PIC You will see that the impeller does not rotate. It acts like a compass and remains stationary. This is how it SHOULD act when properly operating.

Looking at the issue more technically, there are no known effects from either the weak or strong forces.  The earth’s magnetic field has a vertical component everywhere but the equator, and this component creates a torque on the magnet mounted on the impeller shaft. Although the earth’s field does provide a weak aligning force, which causes the impeller to oscillate as it comes to a stop, there is NO effect on the accuracy of the windspeed reading. This is because the force acting on the impeller is “conservative” – it has no effect on the rotation speed. The conservative force causes acceleration of the impeller in equal and opposite measure to the deceleration every time the impeller completes an entire rotation.

Rest Assure that any new impeller from NK has been calibrated and tested to be well within the specified accuracy of plus/minus 3% (our recent test have been much closer to ±2%). The impeller needs NO ADJUSTMENT.  If your Kestrel® application involves hours of intense high-speed use, you may want to consider purchasing a replacement impeller ($19.00) once a year to ensure that your Kestrel maintains factory specified accuracy.

To take an immediate measurement, you must keep the air moving around the temperature sensor.  If there is a strong breeze, just point the Kestrel into the wind. If there is no wind, swing the Kestrel® around in a circle on its lanyard or rapidly wave it back and forth in hand. This ensures that the sensor measures the temperature of the air rather than the temperature of the case.

Alternatively, if you have time, allow the Kestrel to rest where you want to measure the air temperature (NOT in your hand) until the case temperature equalizes with the air temperature. When equalized, the display will read a constant value.  Be aware that this could take as long as twenty minutes.

If the humidity sensor housing (located above the rear label) is wet, the Kestrel cannot take an accurate humidity reading. If the sensor does become wet, shake the unit vigorously to remove the water, and then let it dry completely before use. If the sensor comes in contact with salt water, rinse it thoroughly with clean water, then shake it and allow it to dry.

The humidity sensor has been factory calibrated to be accurate to within ±3%. If your Kestrel appears to no longer meet this specification, it may need to be recalibrated. NK now offers a Relative Humidity Calibration Kit for your home use.