Kestrel Spec Chart

Posted August 26 2013
Measurement
Response Time
Units Operational Range Resolution Accuracy
(+/-)
Specification Range
Wind Speed
1 second  
m/s 0.4 to 60.0 m/s 0.1 Larger of 3% of reading or least significant digit 0.4 to 40.0 m/s
ft/min 59 to 11,948 ft/min 1 59 to 7877 ft/min
km/h 1.0 to 218.0 km/h 0.1 1.0 to 144.0 km/h
mph 0.8 to 135.0 mph 1 0.8 to 89.0 mph
knots 0.6 to 118.3 kt 0.1 0.6 to 78.0 kt
Beaufort 0 to 12 B 0.1 0 to 12 B
1 inch diameter impeller with precision axle and sapphire bearings. Off-axis accuracy -1% @ 5º off-axis; -2% @ 10º; -3% @ 15º.  Calibration drift < 1% after 100 hours use at 16 MPH / 7 m/s. Sustained operation above 60 MPH / 27 m/s will wear impeller rapidly and may cause destruction of impeller.  Replacement impeller (NK PN-0801) may be field-installed without tools (US Patent 5,783,753).
Temperature
1 second
°F -49.0 to 257.0 °F 0.1 1.8 °F -20.0 to 158.0 °F
°C -45.0 to 125.0 °C 0.1 1.0 °C -29.0 to 70.0 °C
Measures air, water and snow temperature.  Thermally isolated, hermetically sealed, precision thermistor mounted externally (US Patent 5,939,645).  Calibration drift negligible.
Relative Humidity
1 minute 
%RH 0.0 to 100.0 % 0.1 3.0 %RH  5.0 to 95.0 % non-condensing
Polymer capacitive humidity sensor mounted in thin-walled chamber external to case for rapid, accurate response (US Patent 6,257,074).  (To achieve stated relative humidity accuracy, unit must be permitted to equilibrate to external temperature when exposed to large, rapid temperature changes and must be kept out of direct sunlight.)  Calibration drift +/- 2% over 24 months. Relative humidity may be recalibrated at factory or in field using Kestrel Humidity Calibration Kit (NK PN-0802).
Pressure  
1 second  
(mb & PSI 4000 model only)
inHg 0.3 to 32.5 inHg 0.01 0.05 inHg At 77.0 °F, 22.1 to 32.5 inHg
hPa / mb 10.0 to 1100.0 hPa / mb 0.1 1.5 hPa / mb At 25.0 °C, 750 to 1100 hPa / mb
PSI 0.15 to 16.0 PSI 0.01 0.02 PSI At 77.0 °F, 10.9 to 16.0 PSI
Monolithic silicon piezoresistive pressure sensor with second-order temperature correction. Maximum error over temperature range 32 to 158 °F (0 to 70°C) , +/- 0.06 inHg / +/-2.0 hPa. Calibration drift typically -0.03 inHg / -1.0 hPa per year. Pressure sensor may be recalibrated at factory or in field.
Altitude  
1 second  
ft -6000 to 30000 ft 1 50 ft At 77.0 °F, <19,700 ft. Max error +/- 98 ft
m -2000 to 9000 m 1 15 m At 25.0 °C, <6,000 m.  Max error +/- 30 m
Temperature compensated pressure (barometric) altimeter. 
Wind Chill 
1 second  
°F 0.7 to 135.0 MPH, -49.0 to 257.0 °F 0.1 1.8 °F 1.8 to 89.0 mph, -50.0 to 50.0 °F
°C 0.4 to 60.0 m/s, -45.0 to 125.0 °C 0.1 1.0 °C 0.4 to 40 m/s, -45.6 to 10.0 °C
Calculated from the primary measurements of wind speed and temperature. Utilizes the NWS Wind Chill Temperature (WCT) Index, revised 2001, with wind speed adjusted by a factor of 1.5 to yield equivalent results to wind speed measured at 10 m above ground.  (Specification temperature limits established by WCT Tables.)
Heat Index  
1 minute  
°F 0.0 to 100.0 %RH, -49.0 to 257.0 °F 0.1 3.6 °F 70.0 to 130.0 °F, 0 to 100% RH
°C 0.0 to 100.0 %RH, -45.0 to 125.0 °C 0.1 2.0 °C 21.1 to 54.4 °C, 0 to 100 %RH
Calculated from the primary measurements of temperature and relative humidity.  Utilizes the NWS Heat Index (HI) tables.  (Specification temperature limits established by HI tables.) 
Dewpoint 
1 minute  
°F 0.0 to 100.0 %RH, -49.0 to 257.0 °F 0.1 3.6 °F -20.0 to 158.0 °F, 20.0 to 95.0% RH
°C 0.0 to 100.0 %RH, -45.0 to 125.0 °C 0.1 2.0 °C -29.0 to 70.0 °C, 20.0 to 95.0 %RH
Calculated from the primary measurements of temperature and relative humidity. Temperature to which the air would need to be cooled at a constant pressure to become saturated.
Wet Bulb Temperature 1 minute   °F -49.0 to 257.0 °F, 0.0 to 100.0 %RH, 8.86 to 32.48 inHg 0.1 3.6 °F 32.0 to 100.0 °F, 5.0 to 95.0% RH, 8.86 to 32.48 inHg, <19700 ft
°C -45.0 to 125.0 °C, 0.0 to 100.0 %RH, 300.0 to 1100.0 hPa 0.1 2.0 °C 0.0 to 37.8 °C, 5.0 to 95.0 %RH, -2000.0 to 9000.0 hPa, <6000 m
Calculated from the primary measurements of temperature, relative humidity and pressure. Temperature indicated by a wet bulb psychrometer.
Max/Avg
Wind Speed
One-button clear and restart of Max Wind Gust and Average Wind measurement.
Pressure Trend Continuously updating three-hour barometric pressure trend indicator:  rising rapidly, rising, steady, falling, falling rapidly.
Display Reflective 4 digit LCD.  Digit height 0.36 in / 9 mm.
Display Update 1 second.
Display Backlight Aviation green electroluminescent backlight.
Clock / Calendar Real-time hours:minutes clock.
Operational Temperature Range
(LCD and Batteries)
The operational temperature range of the liquid crystal display and batteries is 14° F to 131° F / -10 °C to 55 °C. Beyond the limits of the operational temperature range, the unit must be maintained within range and exposed for minimum time necessary to take reading.
Storage Temperature -22 °F to 140 °F / -30 °C to 60 °C.

Auto Shutdown

After 45 minutes of no key presses.
Certifications CE certified. Individually tested to NIST-traceable standards (written certificate of tests available at additional charge).  
Batteries CR2032, one, included. Average life, 300 hours of use, +/-depending on backlight use.
Environmental Waterproof (IP67 standard). Drop-tested (MIL.STD.810F; unit only. Substantial impact may damage replaceable impeller.).
Dimensions Unit 4.8 x 1.7 x 0.7 in / 122 x 42 x 18 mm.  Case 4.8 x 1.9 x 1.1 in / 122 x 48 x 28 mm.
Weight Unit 2.3 oz / 65 g.  Case 1.3 oz / 37 g.