What Makes a Kestrel So Special?
Certified and Guaranteed Accuracy
Every single Kestrel Weather & Environmental Meter 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, NK can even provide a NIST-traceable Certificate of Calibration that specifies exactly which values were measured in each multi-point calibration, and details the calibrated standard used for testing. Our 30-day satisfaction guarantee covers accuracy concerns as well. If a customer questions their unit’s accuracy after purchase, they can contact us and we’ll double-check every calibration to verify the unit meets specifications.
The entire Kestrel line is designed and built in the USA – no other handheld weather meter is. Some electronic components have to be sourced overseas these days, but we buy American wherever we can. We believe US manufacturing is the only way we can ensure that every Kestrel will do its job right, and we also believe it’s important to do our part to keep manufacturing alive and well in the US.
Patented Removable Impeller
The Kestrel impeller measures 1 inch across and is mounted on a nylon bearing. 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 for $19 and popped in without tools, restoring like-new performance. We designed and patented this removable impeller technology, and it keeps Kestrel Meters accurately measuring the wind speed for years.
Patented Dual Temperature Sensor RH Measurement
Relative humidity is tricky to measure – particularly in a sealed product. But, with wildland firefighters among our leading customers, we know it is essential that we get it right. Firefighters 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 achieve its stated accuracy (typically 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.
Patented Temperature Measurement
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.
Pressure Corrected Wet Bulb Temperature
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.
Reliable Delta T
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 new 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.
Leak and Drop Testing
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, we 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 lineup to MIL-STD-810F.
Field and Factory Recalibration
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 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 our almost 30 years of manufacturing Kestrels, we’ve never come across one that needed to be recalibrated.
We offer NIST-traceable Certificates of Calibration for industries that require it.