It is critical to measure relative humidity, wind speed and wind direction in order to minimise waste and maximize safety when crop spraying. In hot, dry conditions, expensive chemicals may evaporate into the air rather than onto your crops. Delta T allows you to accurately assess acceptable spraying conditions to ensure you’re within guidelines and help you select the right spray nozzle. The Kestrel 3500 DT is the difference between wet bulb and dry bulb temperatures and is an accurate predictor of chemical evaporation rates. The Kestrel 3500 Delta T incorporates barometric pressure correction in its wet bulb temperature calculation, ensuring accuracy even on low pressure days, at high altitudes, and in very dry weather. No other pocket weather meter offers this feature with this level of accuracy.
Features
• Simple 3-Button Control
• Large easily read LCD display with backlight
• Standard user replaceable CR2032 Coin Cell Battery (Average Life 300 Hours)
• Data Hold Function
• Drop-Tested (MIL-STD-810F)
• Certificate of Conformity
• Neck Lanyard
• Patented Impeller and Sensor Technology (user-replaceable)
• Slip-On/Off Protective Cover
• Time of Day
• Waterproof & Floats
• 5 Year Warranty
Specification
| Primary Measurement | Units | Resolution | Accuracy (+/-) |
Range: Max Operational Specification (if less) |
Notes |
| Wind Speed or Air Velocity |
m/s | 0.1 | Larger of 3% of reading, least significant digit or 20 ft/min | 0.6 to 60.0 m/s 0.6 to 40.0 m/s |
1 inch diameter impeller with precision axle and low-friction Zytel® bearings. Start-up 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 start-up. Off-axis accuracy -1% @ 5° off-axis; -2% @ 10° -3% @ 15°. Calibration drift < 1% after 100 hours use at 16 MPH | 7 m/s. Replacement impeller (NK PN-0801) field installs without tools (US Patent 5,783,753). |
| ft/min | 1 | 18 to 11,811 ft/min 118 to 7,874 ft/min |
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| km/h | 0.1 | 2.2 to 216.0 km/h 2.2 to 144.0 km/h |
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| mph | 0.1 | 1.3 to 134.2 mph 1.3 to 89.5 mph |
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| knots | 0.1 | 1.2 to 116.6 knots 1.2 to 77.8 knots |
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| Beaufort | 1 | 0 to 12 B | |||
| Temperature | °F | 0.1 | 1.8 °F | -49.0 to 257.0 -20.0 to 158.0 |
Air, water or snow temperature. 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 insulation effect. Calibration drift negligible. |
| °C | 0.1 | 1.0 °C | -45.0 to 125.0 -29.0 to 70.0 |
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| Relative Humidity | %RH | 0.1 | 3.0 %RH | 0.0 to 100.0% 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 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 +/- 2% over 24 months. RH may be recalibrated at factory or in field using Kestrel Humidity Calibration Kit (NK PN-0802). |
| Pressure | inHg | 0.01 | typical 0.04 inHg max 0.07 inHg |
0.30 to 32.48 inHg | Air pressure at the location. Adjustable reference altitude allows display of station pressure or barometric pressure corrected to MSL. Monolithic silicon piezoresistive pressure sensor with second-order temperature correction. Pressure sensor may be recalibrated at factory or in field. Kestrel 2500 and 3500 display continuously updating three-hour barometric pressure trend indicator: rising rapidly, rising, steady, falling, falling rapidly. Kestrel 4000 series displays pressure trend through graphing function. |
| hPa (mb) | 0.1 | typical 1.5 hPa max 2.5 hPa |
300.0 to 1100.0 hPa 10.0 to 1100.0 hPa | ||
| Wet Bulb Temperature (Psychrometric) | °F | 0.1 | 3.6 °F | Refer to stated ranges for temp., relative humidity and pressure. | Temperature indicated by a wet bulb psychrometer under forced aspiration. Calculated from temperature, relative humidity and pressure. |
| °C | 0.1 | 2.0 °C | |||
| Dewpoint | °F | 0.1 | 3.6 °F | Refer to stated ranges for temp. and relative humidity. | Temperature to which the air must be cooled at a constant pressure for water vapour to condense into water. Calculated from temperature and relative humidity. |
| °C | 0.1 | 2.0 °C | |||
| Delta T | °F | 0.1 | 5.4 °F | Refer to stated ranges for temp., relative humidity and pressure. | Difference between dry bulb temperature and wet bulb temperature. When spraying, indicates evaporation rate and droplet lifetime. Safe range for pesticide spraying is 4 to 16 °F / 2 to 9 °C. |
| °C | 0.1 | 3.0 °C | |||
| Altitude | ft | 1 | typical 50 ft max 98 ft |
-2,300 to 85,000 ft | Height above Mean Sea Level (“MSL”). Temperature compensated pressure (barometric) altimeter requires accurate reference barometric pressure to produce maximum absolute accuracy. |
| m | 1 | typical 15 m max 30 m |
-700 to 25,900 m | ||
| Max/Avg Wind | One-button clear and restart of Max Wind Gust and Average Wind measurement by powering down and restarting unit. | ||||
| Display & Backlight | Reflective 5 digit LCD. Digit height 0.36 in / 9 mm. Choice of aviation green or visible red (NV models only) electroluminescent backlight. Manual activation with auto-off. | ||||
| Response Time & Display Update | All measurements except those based on relative humidity respond accurately within 1 second. Relative humidity and all measurements which include RH in their calculation may require as long as 1 minute to fully equilibrate to a large change in the measurement environment. Display updates every 1 second. | ||||
| Clock / Calendar | Real-time hours:minutes clock. | ||||
| Operational & Storage Temperature Range | The operational temperature range of the liquid crystal display and batteries is 14° F to 131° F / -10 °C to 55 °C. Measurements beyond the operational range can be taken by briefly exposing unit to extreme conditions such that the display and batteries remain within the operational range. Storage range -22 °F to 140 °F / -30 °C to 60 °C. | ||||
| Auto Shutdown | After 45 minutes of no key presses. | ||||
| Certifications | CE certified, RoHS and WEEE compliant. Individually tested to NIST-traceable standards (written certificate of tests available at additional charge). | ||||
| Battery | CR2032, one, included. Average life, 300 hours. Battery life reduced by backlight use in 2000 to 3500 models. | ||||
| Environmental | Waterproof (IP67 and NEMA-6). MIL-STD-810F, Transit Shock, Method 516.5 Procedure IV; unit only; impact may damage replaceable impeller. | ||||
| Size & Weight | 4.8 x 1.9 x 1.1 in / 12.2 x 4.8 x 2.8 cm, 3.6 oz / 102 g (including slip-on cover). | ||||
| Colour Options | Yellow | ||||
The manufacturer reserves the right to amend the specification and therefore the information in this document may be subject to change.
Documentation
Data sheet
User Instruction Manual
