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Kestrel 3550AG Agriculture Weather Meter Sensor Specifications

Sensor Specifications

Wind Speed
Units of Measure: mph | kt | B | m/s | ft/min / km/h 
Specification Range:
  • 0.6 to 40.0 m/s
  • 118 to 7,874 ft/min
  • 2.2 to 144.0 km/h
  • 1.3 to 89.5 mph
  • 1.2 to 77.8 knots
  • 0 to 12 B*
  • 2-131.2 F/S*
Operational Range:
  • 0.6 to 60.0 m/s
  • 118 to 11,811 ft/min
  • 2.2 to 216.0 km/h
  • 1.3 to 134.2 mph
  • 1.2 to 116.6 knots
  • 0 to 12 B*
  • 2-196.9 F/S*
Resolution:
  • 0.1 m/s
  • 1 ft/min
  • 0.1 km/h
  • 0.1 mph
  • 0.1 knots
  • 1 B
Accuracy (+/-): Larger of 3% of reading, least significant digit or 20 ft/min
Notes: 1 inch|25 mm diameter impeller with precision axle and low-friction Zytel® bearings. Startup speed stated as lower limit, readings may be taken down to 0.4 m/s | 79 ft/min | 1.5 km/h | .9 mph | .8 kt after impeller startup. Off-axis accuracy -1% @ 5º off-axis; -2% @ 10º; -3% @ 15º. Calibration drift < 1% after 100 hours use at 16 MPH | 7 m/s. Replacement impeller (PN-0801) field installs without tools (US Patent 5,783,753). Wind speed calibration and testing should be done with triangle on impeller located at the top front face of the Kestrel. *F/S only in Ballistics units. Beaufort not available in Ballistics units.

Ambient Temperature
Units of Measure: Fahrenheit, Celsius
Specification Range:
  • -20.0 to 158.0 °F
  • -29.0 to 70.0 °C
Operational Range:
  • 14.0.0 to 131.0 °F
  • -10.0 to 55.0 °C
Resolution:
  • 0.1 °F
  • 0.1 °C
Accuracy (+/-):
  • 0.9 °F
  • 0.5 °C
Notes: Hermetically sealed, precision thermistor mounted externally and thermally isolated (US Patent 5,939,645) for rapid response. Airflow of 2.2 mph|1 m/s or greater provides fastest response and reduction of insolation effect. Calibration drift negligible. Thermistor may also be used to measure temperature of water or snow by submerging thermistor portion into material -- remove impeller prior to taking submerged measurements and ensure humidity sensor membrane is free of liquid water prior to taking humidity-based measurements after submersion.

Pressure
Units of Measure: inHg, hPA, mb
Specification Range:
  • 25°C/ 77°F
  • 750-1100 hPa|mbar
  • 22.15-32.48 inHg
  • 10.88-15.95 PS
Operational Range:
  • 0.30 to 48.87 inHg
  • 10.0 to 1654.7 hPa|mbar
  • 0.14 to 24.00 PSI
  • 14.0 to 131.0 °F -10.0 to 55.0 °C
Resolution:
  • 0.1 hPa|mbar
  • 0.01 inHg
  • 0.01 PSI
Accuracy (+/-):
  • 1.5 hPa|mbar
  • 0.044 inHg
  • 0.022 PSI
Notes: Monolithic silicon piezo-resistive pressure sensor with second-order temperature correction. Between 1100–1600 mbar, unit will operate with reduced accuracy. Sensor may not operate above 1600 mbar and can be damaged above 6,000 mbar or below 10 mbar. Calibration drift is negligible for the life of the product.

Relative Humidity
Units of Measure: %
Specification Range: 5 to 95% 25°C non-condensing
Operational Range: 0 to 100% 
Resolution: 0.1 %RH
Accuracy (+/-): 3%RH
Notes: To achieve stated accuracy, unit must be permitted to equilibrate to external temperature when exposed to large, rapid temperature changes and be kept out of direct sunlight. Calibration drift is typically less than ±0.25% per year.

Calculated Measurements

Wind Chill
Accuracy (+/-):
  • 1.6 °F
  • 0.9 °C
Resolution:
  • 0.1 °F
  • 0.1 °C
Sensors employed:
  • Wind Speed
  • Temperature

Barometric Pressure
Accuracy (+/-):
  • 0.07 inHg
  • 2.4 hPa|mbar
  • 0.03 PSI
Resolution:
  • 0.01 inHg
  • 0.1 hPa|mbar
  • 0.01 PSI
Sensors employed:
  • Pressure
  • User Input (Reference Altitude)

Altitude
Accuracy (+/-):
  • typical: 23.6 ft/7.2 m
  • from 750 to 1100 mBar
  • max: 48.2 ft/14.7 m
  • from 300 to 750 mBar
Resolution:
  • 1ft
  • 1m
Sensors employed:
  • Pressure
  • User Input (Reference Pressure)

Dew Point
Accuracy (+/-):
  • 3.4 °F
  • 1.9 °C
  • 15-95% RH.
  • Refer to Range
    for Temperature Sensor
Resolution:
  • 0.1 °F
  • 0.1 °C
Sensors employed:
  • Temperature
  • Relative Humidity

Wet Bulb Temperature - Psychrometric
Accuracy (+/-):
  • 3.2 °F
  • 1.8 °C
Resolution:
  • 0.1 °F
  • 0.1 °C
Sensors employed:
  • Wind Speed
  • Temperature

Delta T
Accuracy (+/-):
  • 3.2 °F
  • 1.8 °C
Resolution:
  • 0.1 °F
  • 0.1 °C
Sensors employed:
  • Temperature
  • Relative Humidity
  • Pressure

THI (NRC)*
Accuracy (+/-):
  • 1.5 °F
  • 0.8 °C
Resolution:
  • 0.1 °F
  • 0.1 °C
Sensors employed:
  • Temperature
  • Relative Humidity
Notes: * The NRC THI equation is defined as: *THI = (1.8 X Tdb +32) – [(.55 - .0055 X RH) X (1.8 X Tdb-26)] (National Research Council, 1971) where Tdb is dry bulb temperature in °C and RH is relative humidity expressed as a %. This is the equation referenced by Ontario Ministry of Agriculture, Food, and Rural affairs; Journal of Dairy Science; and the University of Arizona. The YOUSEF THI equation is defined as: THI = Tdb + (0.36 × Tdp) + 41.2 (Yousef, 1985) where Tdb is dry bulb temperature in °C and Tdp is dew point temperature in °C. This is the equation referenced by Dairy Australia, University of Missouri, and USDA.

THI (Yousef)*
Accuracy (+/-):
  • 2.3 °F
  • 1.3 °C
Resolution:
  • 0.1 °F
  • 0.1 °C
Sensors employed:
  • Temperature
  • Relative Humidity
Notes: * The NRC THI equation is defined as: *THI = (1.8 X Tdb +32) – [(.55 - .0055 X RH) X (1.8 X Tdb-26)] (National Research Council, 1971) where Tdb is dry bulb temperature in °C and RH is relative humidity expressed as a %. This is the equation referenced by Ontario Ministry of Agriculture, Food, and Rural affairs; Journal of Dairy Science; and the University of Arizona. The YOUSEF THI equation is defined as: THI = Tdb + (0.36 × Tdp) + 41.2 (Yousef, 1985) where Tdb is dry bulb temperature in °C and Tdp is dew point temperature in °C. This is the equation referenced by Dairy Australia, University of Missouri, and USDA.

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