Factory Recalibration / Certification
The Kestrel should be recalibrated if the Relative Humidity (RH) sensor has shown drift in its RH measurement. The Kestrel RH sensor is specified to develop less than 2% drift over 24 months. You may return your Kestrel meter to Nielson Kellerman (NK) for Factory Recalibration of the relative humidity and the related measurements. Recalibration is available with and without certification of NIST traceability and calibration stickers. NK can recalibrate and certify any of the values measured by your Kestrel meter, including: wind speed / air flow; temperature; barometric pressure and humidity. Please contact NK for more information about Factory Recalibration and certification.
Factory calibration for the Kestrels is done at 32.8% and 75.3%.
For RH Field Calibration, purchase this Calibration Kit, for basically unlimited calibrations with only needing replacement salts.
For Wind Calibration, all you need is a new Impeller. Each impeller is tested in the US factory wind tunnel and get thrown off when dropped, hit by debris, or periods of exposure to dust (in mines).
How often should you calibrate your meter?
Largely it’s dependent on whether it’s industrial use or consumer use. Acousticians recalibrate annually, firefighters annually or semi-annually, and general consumers might recalibrate them every 4 or 5 years or so. The official stance is that a calibration is recommended every 24 months due to the possibility of up to 2% calibration drift over 24 months.
If you're Kestrel Meter is flashing 'E1', this means the humidity sensor needs to be re-calibrated. If the unit is less 30 days old (from the date of purchase) you may send it back to NK for re-calibration under warranty. If it has been more than 30 days from purchase, it can be returned to NK for a humidity calibration for $65 (free return shipping). OR - you can buy this calibration kit and do it yourself.
NIST on an Existing Meter: If you need your meter calibrated and tested and NIST certified, you'll want to visit this NIST Existing Meter page. You will find instructions on how to get this done.
NIST on a New Meter: You can purchase your meter on this site, and then add the NIST certification testing from this NIST New Meter page.