Kestrel Calibration Guidelines

Kestrel products are calibrated before they leave the factory. Initially all Kestrel products are guaranteed to be within the specifications stated on the Certificate of Conformity that is provided with each unit. To understand the accuracy of your Kestrel once it leaves the factory, please view the Certificate of Conformity related to your Kestrel Device.

Sensor Drift

As the Kestrel unit gets older however, there is the question about whether recalibration is necessary. Below are the stated drifts for each of the sensors found in Kestrel products:

  • Wind Speed - Impeller will drift dependent on usage. Drift will be < 1% at 100 hours of use with 16 mph winds.
  • Temperature - The thermistor should not drift and should not need to be recalibrated for the life of the unit.
  • Pressure - The pressure should not drift and should not need to be recalibrated for the life of the unit.
  • Humidity - The humidity will drift independent of usage. Maximum drift of this sensor will be +/- 0.25% per year. WARNING: Exposure of the humidity sensor to VOCs (Volatile Organic Compounds) can increase the inaccuracy of the humidity sensor and is not covered as "standard drift".
  • Black Globe - The black globe should not drift and should not need to be recalibrated for the life of the unit.
  • Compass - The compass can be field self-calibrated to correct any known errors.

Kestrel Recalibration Recommendations

Wind Speed - Since this is directly dependent on how much the impeller is used, it is hard to recommend an exact timeframe in which it will fall out of calibration. For frequent users, you may want to replace every year. More infrequent users may wait 2-4 years to recalibrate the impeller. To recalibrate the impeller, simply purchase a factory calibrated impeller from our website here: Kestrel Impeller

Humidity - If we assume the maximum drift on the unit per year, the Kestrel would be +/- 1% off after 4 years, regardless of usage. Depending on the customer’s needs, the humidity should be recalibrated every 1 -4 years.

Kestrel Recalibration Options

If you feel that your Kestrel product has a sensor that has deviated outside of the stated range of accuracy (including noted sensor drift), NK will recalibrate your unit at no cost. Please fill out a repair request to facilitate recalibrating this sensor deviation on the Kestrel Service Calibration page or contact techsupport@nkhome.com.

If instead you would like to recalibrate any of the sensors, NK provides several options:

Tune-Up: All factory calibrations relevant to your model are performed, as well as a full functional check, cleaning, and installation of a new impeller and battery. You will receive back a new Certificate of Conformity with the date or service performed. This certificate will just ensure that the unit is again back within factory specifications however test results will not be provided.

Factory Calibration: This is an a la carte option to recalibrate any of the sensors on the unit. This recalibration will not provide any test results but will provide a certificate stating that the sensor in question is back to reading within factory specifications.

NIST Calibration: NK will perform the calibration services and prepare a NIST Calibration Report and Certificate detailing as found and as left values, observed values from the traceable calibration standard, acceptable performance range, and deviation from standard. If required and available for the sensor in question, NK will also restore your unit’s performance to specification by replacing the sensor or entering a calibration adjustment.

Below are more details on the difference between Factory and NIST calibrations.

Measurement NIST Calibration Points Factory Calibration Points Models Correction Included?
Wind Speed / Air Flow ~ 600 fpm
~ 1200 fpm
~ 300 fpm
~ 1200 fpm
All Kestrel Meters Yes - Impeller will be replaced with a new calibrated impeller if required
Temperature -10°C
50°C
1 hour
equilibration
50°C
1 hour
equilibration
2000 and above DROP No - Temperature sensor reading is not correctable. However, it is rare for this sensor to drift out of specification.
Black Globe Temperature -10°C
50°C
1 hour
equilibration
50°C
1 hour
equilibration
4400, 5400 No - Temperature sensor reading is not correctable. However, it is extremely rare for this sensor to drift out of specification.
Humidity ~ 33% Rh
~ 75% Rh
~ 33% Rh
~ 75% Rh
3000 & 3500
4000 Series
Yes - Sensor will be corrected to perform within specification.
5 Series
DROP D2, D3
For the DROPs the humidity sensor is not adjustable. However, it is rare for this sensor to drift out of specification.
Pressure Ambient Pressure
Lower Limit Pressure
  2500 & 3500
4000 Series
5 Series
Yes - Sensor will be corrected.

Warranty Information

All warranties are measured from the date of the product's purchase by the first consumer end user. If no proof of purchase is available, the warranty period will be measured from the manufacture date of the product purchased as determined by serial number.

NK will repair, recalibrate or replace with the same or equivalent product, at NK's option, any defective product or part when notified within the warranty period. NK may use new or reconditioned parts in performing limited warranty repairs and building replacement products. NK will return the product via domestic ground shipping or NK's choice of method of international shipping at no charge. Upgraded shipping is available at customer expense. Repair or replacement under the terms of this limited warranty does not extend or renew the warranty period.

The following do not result from a manufacturing defect and are not covered under this limited warranty:

  • Damage due to improper use or neglect (including corrosion)
  • Damage resulting from impact significantly exceeding stated impact standard, crushing or mechanical harm
  • Damage due to exposure of toxic or corrosive gases - including for example chlorine, ammonia, hydrogen sulfide, etc.
  • Modifications, alterations or attempted repairs by someone other than an authorized NK repair agent
  • Water damage resulting from exposure to water after product enclosure has been visibly damaged and/or failure to return product for service promptly after product enclosure has been compromised.
  • Impeller failure not caused by a manufacturing defect
  • Normal wear and tear
  • Accuracy issues resolvable by recalibration
  • Reduction in capacity of rechargeable batteries or battery packs age normal for their age and/or number of charge/discharge cycles
  • Failed batteries other than an NK rechargeable battery pack and/or damage resulting from corrosion or leakage of any installed batteries other than an NK rechargeable battery pack

Kestrel Calibration