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Home > Products > Kestrel Hand-held Weather Meters > Unique Kestrel Features
click image above for details of the Kestrel Weather Meter's unique features
At Richard Paul Russell Ltd and Nielsen-Kellerman, weather is serious business!
RPR Ltd have been involved with the Kestrel wind and weather instruments since the conception and design of the original Kestrel 1000 hand-held wind meter back in 1994. NK have been researching, designing, manufacturing and distributing the Kestrel Meters ever since.
NK's founders and lead engineers, Richard Kellerman and Paul Nielsen, are determined to make the most accurate and reliable hand-held weather devices available. They have developed four patented measurement technologies for the Kestrel family and continue to research ways to improve the Kestrel line and create new products to meet their customers' needs.
While it may not be obvious when you look at a Kestrel side-by-side with a competitor's weather meter, there are very important differences that make Kestrel the best choice for almost every application.
Every single Kestrel manufactured at NK is calibrated for every single value, either directly against NIST-traceable standards or against an intermediary standard calibrated daily. (The National Institute of Standards and Technologies is the federal technology agency that works with industry to develop and apply technology, measurements, and standards.)
Every unit is shipped with a FREE Certificate of Conformity that states what calibrations were performed, and the certified performance specifications.
What does that mean for the customer? They can be absolutely sure that their weather readings are accurate to the stated specifications. Some competing weather instruments claim the same specifications as Kestrel, but only Kestrel certifies their accuracy.
For an additional charge, RPR Ltd can provide a Certificate of Calibration that specifies exactly which values were measured in each multi-point calibration, and provides traceability of measurements to recognised National Standards.
The Kestrel impeller measures 1 inch across and turns on a Swiss precision pivot mounted on low-friction Zytel® bearings. Its large size ensures accurate readings even if pointed off-angle from the wind, and its very low start-up speed allows measurement of the lightest puffs of wind. Units with smaller impellers simply can't match the Kestrel's performance at low wind speeds.
If damaged, a new calibrated impeller can be purchased and popped in without tools, restoring like-new performance. NK designed and patented this removable impeller technology, and it keeps Kestrel Meters accurately measuring the wind speed for years.
Relative humidity is tricky to measure - particularly in a sealed product. But, with wild land fire-fighters among Kestrel's leading customers, NK know it is essential to get it right.
Fire-fighters typically work in extreme conditions with very low humidity levels, and their lives literally depend on accurate readings. Accurate temperature measurement is critical to calculating relative humidity.
That's why NK developed the patented Kestrel dual temperature sensor configuration. It is not necessary to wait the 20 to 40 minutes that would normally be required for the unit temperature to equilibrate to the air temperature after a temperature shift. So long as airflow over the temperature sensor is maintained, either by holding it into a breeze or waiving it in the air, the external temperature sensor will provide instant and accurate readings of the outside air temperature, while the second sensor in the humidity chamber provides the critical information about the internal unit temperature (even if different).
The Kestrel then performs the calculations necessary to yield relative humidity accuracy of +/- 3%RH from 5 to 95% (both impressive statistics usually only found in units costing hundreds of dollars more).
The humidity sensor in the Kestrel has been selected for long-term stability and reliable performance even at very low and very high humidity conditions. Every Kestrel is calibrated against NIST-traceable standards, and can be recalibrated in the field with the Kestrel RH kit.
Unlike most watches and other products with a temperature measurement, the Kestrel sensor is outside the case to ensure it measures the air, not your hand or pocket. The "curls" serve to further isolate the temperature sensor from the effects of the case temperature. Again, simply wave the Kestrel back and forth a few times and you'll have accurate air temperature readings in seconds.
And, since the Kestrel is completely waterproof, you can actually take water temperature and snow temperature readings - simply submerge the sensor in the water or snow. Just ask the US Biathlon team - they used Kestrel 4000's in the 2006 Winter Olympics to measure air and snow temperature to determine the appropriate wax to use on their skis.
Meters that provide wet bulb temperature readings without a pressure sensor assume standard atmospheric conditions, leading to highly inaccurate readings on low-pressure days, at high altitudes, or in any other "non-standard" situation. Kestrel meters only offer wet bulb temperature readings on our pressure-sensor equipped units, ensuring accuracy in all conditions.
Delta T is a reading commonly used in dry climates to provide a quick guide to acceptable spraying conditions. It's the spread between the wet bulb temperature and the dry bulb temperature. For example, it is not recommended to apply pesticides when Delta T is above10 - a range of 2 to 8 is ideal.
With the Kestrel 3500 Delta T, the calculation is done for you, accurately and simply. Because the wet/dry bulb spread can be quite small, even a small error in either temperature reading will generate a large percentage of error in Delta T. The Kestrel 3500 Delta T does correct for pressure, ensuring that Delta T is measured accurately.
NK specifies IP-67 sealing for every Kestrel. This means that a Kestrel is totally protected from dust and can be submerged in water to 1 m (3ft) for up to 30 minutes without any leakage.
To ensure that each Kestrel meets this standard, NK subject each one to a vacuum leak test after final assembly. We've heard of one Kestrel product tester who sank it in a lake for a full day of fishing, then pulled it out and put it back to work (that's dedication!), and the appearance of Kestrel meters employed in underground coal mines is testimony to their dust-resistance. We have also drop-tested the Kestrel line-up to MIL-STD-810F.
Not only is every Kestrel guaranteed accurate when it leaves the factory, but accuracy can be ensured by field and factory recalibration for years of reliable performance.
Many highly technical applications require that measurement tools be recalibrated on a regular schedule. Relative humidity, wind, and barometric pressure measurements on each Kestrel can be calibrated in the field, no matter how old the Kestrel.
To restore the wind speed calibration, the user need simply replace the impeller.
To calibrate the relative humidity, the customer can employ the Kestrel Field Calibration Kit or send their unit back to us for return to NK for factory recalibration.
Recalibration of the barometric pressure is also possible so long as the user has a source of an accurate pressure reading. (Instructions are posted on our web site or the unit can be returned for factory calibration.)
The only sensor that cannot be recalibrated is the temperature sensor, but in more than 10 years of manufacturing Kestrels, NK have never come across one that needed to be recalibrated.
Kestrels are sold with a 30-day satisfaction guarantee, and a 5-year warranty. NK's track record speaks for itself - the return rate for the entire Kestrel line for any reason is 0.002%.
Even after the regular warranty expires, NK cover every Kestrel FOR LIFE with their Customer Care Warranty Program, which allows users to trade in a used or damaged Kestrel for a new one at a considerable discount. For any such unit purchased in the UK from RPR Ltd a replacement unit may be offered at a 45% discount off our current retail price.
If you ever have a problem or question about your Kestrel, you can come straight to us at RPR Ltd in the UK or NK in the USA.
The Bluetooth® word mark and logos are registered trademarks owned by Bluetooth SIG, Inc. and any use of such marks by Richard Paul Russell Ltd is under license. Kestrel, Kestrel Tracker, Pocket Wind, Pocket Weather and the Kestrel logos are trademarks owned by Neilsen Kellerman. Other trademarks and trade names are those of their respective owners.
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