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).

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.

Max/Avg Wind Speed

One-button clear and restart of Max Wind Gust and Average Wind measurement.

Display

Reflective 3 1/2 digit LCD.  Digit height 0.36 in / 9 mm.

Display Update

1 second.

Display Backlight

Aviation green electroluminescent backlight.

Operational Temperature Range

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.

(LCD and Batteries)

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.