Kestrel 3500FW Fire Weather Meter

$209.00

Measure weather conditions quickly and easily with the trusted tool of firefighters, now with wetbulb and baro/alt measurements included.

Availability: In stock
SKU
0835FWORA
Please fill out the selections below to help us ensure that you're getting the most accurate product




 FREE US SHIPPING

  • Rugged, simple and accurate wind speed, temperature, humidity, and pressure meter.
  • Calculates relative humidity, temperature, average wind speed, altitude, pressure trends and more.
  • Data hold feature, clock and backlit display for night time use.
  • Includes a waterproof PIG/FDFM reference card. Perfect for taking fire weather observations.

Kestrel 3500FW Fire Weather Meter Overview


Environmental Measures
Altitude (Barometric)
Barometric Pressure
Dew Point Temperature
Heat Stress Index
Relative Humidity
Temperature
Wet Bulb Temperature (Psychrometric)
Wind Chill
Wind Speed/Air Speed
Tips For Taking Accurate Measurements

When fighting wild fires, protecting lives, houses, and property while ensuring safety for everyone involved demands accurate fire behavior predictions based upon good weather observations. Kestrel weather meters have been relied upon by fire fighters for decades to provide fast, accurate measurement of wind speed, temperature and humidity. The Kestrel 3500 Fire Weather Meter has been updated specifically for fire fighting, adding barometric pressure, altitude and wet bulb readings and an easy-to-read Probability of Ignition (PIG) and Fine Dead Fuel Moisture (FDFM) reference card – everything required for a complete weather observation.  This one rugged, handheld instrument easily replaces all of the items included in your Belt Weather Kit, providing consistently accurate measurements without prepping a sling psychrometer or risking the possibility of human error.

IP67 waterproof and Mil-SPEC-810G drop tested, Kestrels are built for the abuse that work on a fire line can dish out. The Kestrel 3500 Fire Weather Meter includes a hard, rubberized slip-on cover that protects the display and impeller, even when tossed in your pack. Kestrel Weather & Environmental Meters are designed & manufactured in the U.S.A and are backed by our 5-year warranty. Each Kestrel 3500 is factory calibrated and comes with a certificate of conformity and may be factory or field recalibrated.

Engraving Note: Please make sure that everything is spelled correctly, as your engraved product cannot be returned. All sales are final on engraved products. Add 2 business days to all engraving orders.

Visit the Kestrel Fire Weather Minisite for a more detailed look at this breakthrough tool.

  • 3-Button Control
  • Backlight blue white
  • Data Hold Function
  • Date & Time
  • Drop-Tested to MIL-STD-810G
  • Field Humidity Calibration/Correction Routine
  • Hard Slip-On Protective Cover
  • High Contrast, Sunlight Readable Monochrome LCD Display
  • Minimum/Maximum/Average Reading
  • Pressure Sensor
  • Relative Humidity Sensor
  • Temperature Sensor (Patented External Isolated)
  • Waterproof to IP67 (3'/1M for 30 minutes)
  • Battery - 1 x CR2032
  • Certificate Of Conformity (Spec Sheet)
  • Instructions
  • Lanyard
  • PIG Reference Card (Waterproof)
SENSORS
SENSORS 1
0
0
0
2
0
0
0
2
5
0
0
3
0
0
0
3
5
0
0
3
5
0
0
D
T
3
5
5
0
F
W
3
5
5
0
A
G
ACCURACY
(+/-)*
RESOLUTION SPEC. RANGE OP. RANGE NOTES
Wind Speed | Air Flow Larger of 3% of reading, least significant digit or 20 ft/min 0.1 m/s
1 ft/min
0.1 km/h
0.1 mph
0.1 knots
1 B*
0.1 F/S*
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*
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*
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 (NK 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 0.9 °F
0.5 °C
0.1 °F
0.1 °C
-20.0 to 158.0 °F
-29.0 to 70.0 °C
14.0.0 to 131.0 °F
-10.0 to 55.0 °C
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.
Relative Humidity 3.0 %RH 0.1 %RH 5 to 95%
non-condensing
0 to 100% 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. Humidity sensor may be recalibrated at factory or in field using Kestrel Humidity Calibration Kit (NK PN-0802).
Pressure 1.5hPa|mbar
0.044 inHg
0.022 PSI
0.1 hPa|mbar
0.01 inHg
0.01 PSI
25°C/ 77°F
750-1100 hPa|mbar
22.15-32.48 inHg
10.88-15.95 PS
0.30 to 48.87 inHg
10.0 to 1654.7
hPa|mbar
0.14 to 24.00 PSI
and
14.0 to 131.0 °F
-10.0 to 55.0 °C
Monolithic silicon piezoresistive pressure sensor with second-order temperature correction. Pressure sensor may be recalibrated at factory or in field. Adjustable reference altitude allows display of station pressure or barometric pressure corrected to MSL. Kestrel 4200 displays station pressure on a dedicated screen. 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. PSI display on Kestrel 4000 series only.
Compass
1/16th Cardinal
Scale
0 to 360° 0 to 360° 2-axis solid-state magnetoresistive sensor mounted perpendicular to unit plane. Accuracy of sensor dependent upon unit's vertical position. Self-calibration routine eliminates magnetic error from batteries or unit and must be run after every full power-down (battery removal or change). Readout indicates direction to which the back of the unit is pointed when held in a vertical orientation. Declination/variation adjustable for True North readout.
CALCULATED MEASUREMENTS
MEASUREMENT 1
0
0
0
2
0
0
0
2
5
0
0
3
0
0
0
3
5
0
0
3
5
0
0
D
T
3
5
5
0
F
W
3
5
5
0
A
G
ACCURACY
(+/-)*
RESOLUTION SPEC. RANGE SENSORS EMPLOYED NOTES
Altitude typical:
23.6ft/7.2m
max:
48.2ft/14.7m
1ft
1m
typical:
750 to 1100 mBar
max:
300 to 750 mBar
Pressure User Input (Reference Pressure) Height above Mean Sea Level ("MSL"). Temperature compensated pressure (barometric) altimeter requires accurate reference barometric pressure to produce maximum absolute accuracy. Both accuracy specs corresponds to a reference pressure anywhere from 850 to 1100 mBar.
Barometric Pressure 0.07 inHg
2.4 hPa|mbar
0.01 inHg
0.1 hPa|mbar
Refer to Ranges for Sensors Employed Pressure User Input (Reference Altitude) Air pressure that would be present in identical conditions at MSL. Station pressure compensated for local elevation provided by reference altitude. Requires accurate reference altitude to produce maximum absolute accuracy
Delta T 3.2 °F
1.8 °C
0.1 °F
0.1 °C
Refer to Ranges for Sensors Employed Temperature
Relative Humidity
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.
Dew Point 3.4 °F
1.9 °C
0.1 °F
0.1 °C
15 to 95 % RH
Refer to Range for Temperature Sensor
Temperature Relative Humidity Temperature that a volume of air must be cooled to at constant pressure for the water vapor present to condense into dew and form on a solid surface. Can also be considered to be the water-to-air saturation temperature.
Heat Index 7.1°F
4.0°C
0.1 °F
0.1 °C
Refer to Ranges for Sensors Employed Temperature Relative Humidity Perceived temperature resulting from the combined effect of temperature and relative humidity. Calculated based on NWS Heat Index (HI) tables. Measurement range limited by extent of published tables
Temperature Humidity Index - THI (NRC) 1.5°F
0.8°C
0.1 °F
0.1 °C
Refer to Ranges for Sensors Employed Temperature Relative Humidity
Temperature Humidity Index - THI (Yousef) 2.3°F
1.3°C
0.1 °F
0.1 °C
Refer to Ranges for Sensors Employed Temperature Relative Humidity
Wet Bulb Temperature - Psychrometric 1.6 °F
0.9 °C
0.1 °F
0.1 °C
Refer to Ranges for Sensors Employed Temperature
Relative Humidity
Pressure
Temperature indicated by a sling psychrometer. Due to nature of the psychrometric ratio for a water-air system, this approximates the thermodynamic wet-bulb temperature. The thermodynamic wet-bulb temperature is the temperature a parcel of air would have if cooled adiabatically to saturation temperature via water evaporating into it.
Wind Chill 1.6 °F
0.9 °C
0.1 °F
0.1 °C
Refer to Ranges for Sensors Employed Wind Speed
Temperature
Perceived temperature resulting from combined effect of wind speed and temperature. Calculated based on 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 10m above ground. Measurement range limited by extent of published tables.
ADDITIONAL SPECIFICATIONS
MEASUREMENT 1
0
0
0
2
0
0
0
2
5
0
0
3
0
0
0
3
5
0
0
3
5
0
0
D
T
3
5
5
0
F
W
3
5
5
0
A
G
NOTES
Display & Backlight Reflective 3 1/2 digit LCD. Digit height 0.36 in / 9 mm. Aviation green electroluminescent backlight. Manual activation with auto-off
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.
Max/Avg Wind One-button clear and restart of Max Wind Gust and Average Wind measurement.
Data Upload & Bluetooth® Data Connect Option Requires optional PC interface (USB or RS-232) or Bluetooth data transfer option and provided software.
Bluetooth Data Transfer Option: Adjustable power consumption and radio range from up to 30 ft | 9 meters. Individual unit ID and 4-digit PIN code preprogrammed for easy identification and data security when pairing and transmitting. Employs Bluetooth Serial Port Protocol for data transmission.
Clock / Calendar Real-time hours:minutes clock.
Auto Shutdown After 45 minutes of no key presses.
Languages English
Certifications CE certified, RoHS and WEEE compliant. Individually tested to NIST-traceable standards (written certificate of tests available at additional charge).
Origin Designed and manufactured in the USA from US and imported components. Complies with Regional Value Content and Tariff Code Transformation requirements for NAFTA Preference Criterion B.
Battery Life CR2032, one, included. Average life, 300 hours. Battery life reduced by backlight use in 2000 to 3500 models.
Shock Resistance MIL-STD-810g, Transit Shock, Method 516.6 Procedure IV; unit only; impact may damage replaceable impeller.
Sealing Waterproof (IP67 and NEMA-6).
Operational Temperature Limits 14° F to 131° F | -10 °C to 55 °C Measurements may be taken beyond the limits of the operational temperature range of the display and batteries by maintaining the unit within the operational range and exposing it to the more extreme environment for the minimum time necessary to take reading.
Storage Temperature -22.0 °F to 140.0 °F | -30.0 °C to 60.0 °C.
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).

* NOTE: Accuracy calculated as uncertainty of the measurement derived from statistical analysis considering the combined effects from primary sensor specifications, circuit conversions, and all other sources of error using a coverage factor of k=2, or two standard deviations (2Σ).

Kestrel Basic (1000-3500) Certificates of Comformity

Certificate of Conformity for the Kestrel 1000-3500DT with SNs above 2262687


Models & SKUs:

  • Kestrel 3500 Fire Weather Meter: 0835FWORA

Click here for the Certificate of Conformity and Full Specifications Chart


Support Documents for all Kestrels

Replacing the Kestrel Impeller

Product Safety and Warranty Kestrel 5000 Series

Kestrel Basic (1000-3500) Certificates of Comformity

Certificate of Conformity for the Kestrel 1000-3500DT with SNs above 2262687

Kestrel Basic (1000-3500) Instruction Manuals

User Guide for the Kestrel 1000, 2000, 2500, 2500NV, 3000, 3500, 3500NV, 3500DT, and 3500FW

Product Questions

"All measurements not available in all units"

Temperature Functions

For best accuracy when taking temperature measurements you must keep the air moving around the temperature sensor and keep the Kestrel out of prolonged, direct sunlight. If there is a strong breeze, just point the Kestrel into the wind. If there is no wind, swing the Kestrel around in a circle on its lanyard or rapidly wave it back and forth in hand. This ensures that the sensor measures the temperature of the air rather than the temperature of the case. Alternatively, if you have time, allow the Kestrel to rest where you want to measure the air temperature (NOT in your hand or in direct sunlight if there is no wind) until the case temperature equalizes with the air temperature. When equalized, the display will read a constant value. Be aware that this could take a few minutes, particularly if there is no wind.

Humidity Functions

One reason your Kestrel may not be reading accurate ambient humidity is because of proximity to humidity sources such as your hand, your body or the ground. Avoid covering the large humidity chamber opening on the case rear with your fingers. Keep all fingers below the finger groove and away from the chamber opening. Do not take reading that rely upon humidity with the Kestrel meter lying flat – raise it into the air vertically or stand it on its base and orient it into the wind or air flow. If a high level of accuracy is required for measurements involving humidity, do not hold the unit while taking measurements. Taking readings with the Kestrel in your hand or over your body can raise relative humidity by 5% or more. A Kestrel vane mount will isolate the Kestrel Meter from erroneous humidity influences and keep it oriented into the wind or air flow while taking measurements. Whenever you move your Kestrel Meter into a new environment wait until the primary sensor values have stabilized (Temperature, Humidity, etc.) before taking measurements that rely upon these values. After a large change in environmental condition, this may take 15 minutes or more, with humidity potentially taking the longest. If the humidity sensor housing (located above the rear label) is wet, the Kestrel cannot take an accurate humidity reading. If the sensor does become wet, shake the unit vigorously to remove the water, and then let it dry completely before use. If the sensor comes in contact with salt water, rinse it thoroughly with clean water, then shake it and allow it to dry. As is typical with humidity sensors, it is possible for the humidity sensor in the Kestrel to drift over time as described in the spec sheet. If your unit has a Humidity recalibration function, it can be returned to the factory or used with the Kestrel RH Calibration Kit to recalibrate its humidity readings.

Wind Meter Functions

Wind speed is highly dependent on surrounding obstructions such as buildings, yourself and the ground, with wind speeding up as it flows around and over obstacles and slowing down as it passes behind them. Even in an open area, Wind speed will be slower near the ground so ensure you are taking measurements at an appropriate height for your application. Hold the back of the unit directly into the wind. Holding the unit off-axis by 5° will reduce accuracy by 1%, 10° will reduce accuracy by 2% and 15° will reduce accuracy by 3%. Using a Kestrel Vane Mount will ensure the unit is correctly oriented into the wind and measuring accurate wind speeds. The Kestrel impeller housing can rotate in the unit. For best accuracy, ensure one of the three “arms” of the impeller housing is pointing straight up. The wind speed displayed by the Kestrel Meter is a 3 second rolling average. This allows the unit to provide a value that is more representative of the typical, ambient conditions but not capture peak speeds for instantaneous blasts of air.

Compass Functions

The compass in the Kestrel Meter is used for direction, crosswind, headwind/tailwind as well as for capturing various user inputs based on direction. When calibrating and when using the compass, it is important to hold the unit as vertically as possible. Any tilt in angle present when the unit is calibrated or when measurements are taken will negatively impact the accuracy of the compass reading. Many users will inadvertently tilt the Kestrel Meter away from themselves slightly when holding the unit. If a high level of accuracy is required, using a Kestrel vane mount on a leveled tripod for calibration and measurement can eliminate error.

Pressure Functions

All pressure and altitude measurements are made using the pressure sensor. Some units have a dedicated “Pressure” screen which shows Station Pressure, the raw pressure reading straight from the sensor. The Barometric Pressure measurement (Baro) displays the local Barometric Pressure using the Station Pressure measurement adjusted to the local altitude using the Reference Altitude value input by the user. The Altitude measurement displays the local altitude using the Station Pressure measurement combined with the Reference Baro value input by the user. To obtain an accurate barometric pressure or altitude readings, you must first know EITHER your location’s current barometric pressure OR your current altitude. If the Reference Altitude value is incorrect, the Barometric Pressure reading will also be incorrect. If the Reference Barometric pressure value is incorrect, the Altitude reading will also be incorrect. Because Barometric Pressure and Altitude are each dependent on the alternate reference value remaining constant, Barometric Pressure and Altitude cannot be accurately measured simultaneously. If your unit has a pressure recalibration function, a new Barometric Pressure calibration value may be input. If this value was not taken from a verified source (a local airport or weather station) with the Kestrel being calibrated at the same location as the reference device, pressure related measurements may be incorrect.

WBGT

When changing environments (such as moving form an air conditioned room to outdoors or removing the unit from your pocket) the unit requires between 8-15 minutes to equilibrate to its surroundings before taking readings. Take measurements at least 3 feet off the ground and in the same wind or air flow conditions as the people you are monitoring. Ensure the Kestrel is oriented into the wind and able to measure the full wind value. A tripod or pole mount and the Kestrel Rotating Vane Mount are ideal for ensuring accurate measurements. Differences in the reflectivity of ground surfaces such as grass or asphalt will impact measurements. Be sure to take measurements in the same solar/radiant heat environment as the people you are monitoring. Unlike best practices for other measurements, WBGT is intended to be taken in direct sunlight. As long as there is occasional wind the Kestrel has software that allows it to maintain an accurate WBGT reading despite being placed in direct sunlight.

Air Flow

Kestrel Professional Meters can calculate air flow through a duct by combining user input information about the size and shape of the duct with the measured air velocity. In addition to reading the instantaneous Air Flow off the main measurement screen, a more accurate result may be obtained by capturing an average air flow on the Min/Ave/Max screen while traversing the duct. Traversing consists of dividing the area of the duct into evenly sized sections and averaging the air flows at the center of all sections. By spending an equal amount of time at each measurement location and quickly moving between measurement locations, the average air flow measurement can provide a more accurate measure of the air flow in the duct. Capturing an average can be particularly helpful when measuring ducts with registers or dimensionally uneven air flow.

Air Flow Diagram

Evaporation Rate

(Kestrel 5200 Professional Environmental Meter) Kestrel Professional Meters can calculate a concrete evaporation rate (ACI 308) by combining a user input concrete temperature with measured air temperature, wind speed and relative humidity. Concrete mix temperature is generally measured with a probe or infrared thermometer and should be read at the time of making the evaporation rate measurement After inputting the mix temperature, hold the unit vertically, approximately 20 inches above the surface of the concrete while facing the rear of the unit directly into the wind. To avoid inaccurate Evaporation Rate readings due to thermal loading it is best to shade the Kestrel. (Be sure the source of shade is not obstructing the wind speed measurement.) The ACI recommends taking a 6-10 second average of the evaporation rate to account for fluctuating wind speeds. To measure an average Evaporation Rate, scroll right from the Evaporation Current Measurement Screen to the Min/Ave/Max Screen and press select to manually start and stop a capture.

... Permalink
  1. Start with a known; either current barometric pressure or current altitude. (NK recommends identifying your current altitude since it is constant.)
  2. Enter this reference altitude on the barometric pressure screen.
    • For K1000-K3500 you would enter this by pressing both outside buttons.
  3. Take note of the updated barometric pressure that is shown.
  4. Use this updated barometric pressure as your reference pressure on the altitude screen.
  5. Now your barometric pressure and altitude are set for your current location/conditions. Important note: If you change altitude the barometric pressure will become inaccurate. If a weather system moves in, the altitude will become inaccurate.

For more info check out our YouTube video on Setting Reference Pressure and Reference Altitude on the Kestrel 4000 series!

... Permalink
  1. Barometric Pressure vs. Station Pressure: What's the Difference? Barometric Pressure vs. Station Pressure: What's the Difference? When it comes to measuring barometric pressure, there is a bit of science going on behind the scenes. Let's take a look at the difference between barometric vs. station pressure and the variables that go into calculating the two readings.
  2. Wildland Fire and Weather Monitoring: Saving Lives with Top Technologies Wildland Fire and Weather Monitoring: Saving Lives with Top Technologies Combating wildland fires isn’t for the faint of heart. According to the National Interagency Fire Center, over 1,100 people have died from wildfires in the last 100 years. In the last 10 years, 34,607 wildlife fires were reported over 2,932,334 acres.
  3. Kestrel Meter Found More Accurate Than Sling Psychrometer in Lab Test Accurate weather readings are essential for the safe and effective management of wildland fires. The ideal weather monitoring tool must be easy to use, extremely accurate, and quick to deploy. Both the sling psychrometer and Kestrel Weather Meter have been used for decades by firefighters to gather environmental conditions. Which device performs at the highest level of accuracy? This question was put to the test in a lab setting by PhysioZing, an
  4. Arizona Wildland Firefighters & Kestrel Meters Firefighters battling the Arizona wildfires are relying on Kestrel Pocket Weather Meters to get the critical environmental data required for fire safety and containment. As wildfires continue to spread across the state, firefighters face extreme and dangerous conditions on the fire line. Kestrel meters instantly and accurately provide all the necessary weather information needed to help to save land, homes, and lives.