Kestrel 3500 Delta T Pocket Weather Meter Kestrel 3500 Delta T Pocket Weather Meter
5-Year Warranty on all Kestrels

Kestrel 3500 Delta T Pocket Weather Meter

Product code: K3500DT - 0835DT

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• Designed specifically for farmers and the agricultural market & is used to determine acceptable spraying conditions
• Small, pocket-sized electronic rotating vane type of anemometer
• Built-in temperature, humidity & barometric pressure sensors
• Uses high precision Zytel® bearings & a light weight impeller to provide accurate air flow measurements even at low speeds
• Impeller assembly is replaceable by the user in the case of damage

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• 24 hour order processing Mon-Fri on all in-stock models
• If you're not 100% satisfied return your order within 21 days
• Free standard delivery. Next day delivery available

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This specialist weather meter, for those in the agricultural industry involved in crop spraying, includes the measurement of Delta T. Delta T is the spread between the wet bulb temperature and the dry bulb temperature (in degrees C).

Delta T offers a quick guide to determining acceptable spraying conditions. For example, it is not recommended to apply pesticides when Delta T is above 10 - a range of 2 to 8 is ideal. With the Kestrel 3500 Delta T, the calculation is done for you, accurately and simply.

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 when Delta T monitoring is important. No other pocket weather meter offers this feature with this level of accuracy.

By also measuring other critical conditions, such as relative humidity and wind speed, the kestrel 3500 delta T helps ensure safe and effective spraying.

A trend arrow displays whether the pressure is rising, stable or falling, this trend is calculated over a 3-hour period. The pressure is monitored even when the 3500 Delta T is switched off.

The humidity sensor compensates for temperature changes and is designed for stability and accuracy.

The liquid crystal display has large 9mm high digits and is backlit for a clear readout in low light conditions. Power is from an easily replaceable standard lithium coin type cell, which will typically give up to 300 hours of operation. The instrument automatically switches off if no keys are pressed for 45 minutes.

The Kestrel 3500 Delta T Pocket Weather Meter is made from high impact injection moulded plastic and corrosion resistant materials with the electronics fully sealed. It will float if accidentally dropped into water. There is a hard cover for protection when not in use and a lanyard is provided for added security.

Primary Measurement Units Resolution Accuracy
(if less)
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
km/h 0.1 2.2 to 216.0 km/h
2.2 to 144.0 km/h
mph 0.1 1.3 to 134.2 mph
1.3 to 89.5 mph
knots 0.1 1.2 to 116.6 knots
1.2 to 77.8 knots
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
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.

Case Study
Our following Case Studies give an overview of how this product applies to different sectors.
Please click on the title below to read the full case study.

Emergency Services
Fire Fighting
Health & Safety
Marine, Ships & Harbours
Outdoor Sports
Sport Windsystems
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