Kestrel 4250 User Manual
4250
Racing Weather Tracker
with Backlight
In a hurry?
Be sure to read pages
5-7 to ensure that
your Kestrel is setup
properly!
Instruction Manual for Kestrel 4250
Racing Weather Tracker
1
www.kestrelweather.com 800.784.4221
Revised 07/29/10
Revised 09/07
Kestrel® 4250 Racing Weather® Tracker
3
MANUAL MEMORY
BUTTON Press to manually
store current conditions to
memory.
MEASUREMENT BUTTONS
Press to scroll between
screens: Date/Time,
Measurements, User
Dened Screens
POWER/SETUP BUTTON
Hold to turn power on or
o. Press to enter and exit
Main Setup Menu.
IMPELLER Zytec™
V-bearings on a userreplaceable impeller.
IMPELLER COVER Swivel
cover protects impeller
when not in use.
BACKLIGHT BUTTON
Press to activate
backlight for 1 minute.
MODE BUTTONS Press
to change mode of
measurements: Current,
Min/Max/Avg, Chart.
COMMAND BUTTON
In Chart Screens, press
to view data points. In
Setup Menus, press to
FRONT BACK
make selection.
DATA UPLOAD OPTICAL
COUPLER Software and
serial port interface sold
separately.
BATTERY DOOR Sealed
with o-ring to keep
product watertight.
TEMPERATURE SENSOR
Hermetically sealed precision
thermistor coiled to isolate
from case temperature.
HUMIDITY SENSOR Capacitive
sensor with secondary
thermistor to improve
accuracy and response.
SERIAL NUMBER
PRESSURE SENSOR Monolithic
silicon piezoresistive sensor.
Do NOT insert any objects
into this hole.
AAA BATTERIES
Kestrel® 4250 Racing Weather® Tracker
TABLE OF CONTENTS
GETTING STARTED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
NAVIGATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SPECIAL FUNCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
MAIN SETUP MENU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
APPLICATION EXAMPLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
MEMORY CAPABILITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
DEFAULT SETTINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
FREQUENTLY ASKED QUESTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
CUSTOMER SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Congratulations on the purchase of your Kestrel 4250 Racing Weather Tracker! The Kestrel 4250 is our newest
and most comprehensive Racing-specic instrument. It not only measures EVERY major environmental
condition easily, accurately and right in the palm of your hand, but now also automatically calculates Density
Altitude and Water Grains (Humidity Ratio).
While the Kestrel 4250 is user-friendly and simple to use, reading the instruction manual is recommended in
order to use the Kestrel 4250 to its fullest potential.
NK, manufacturer of Kestrel Pocket Weather Meters, is available to answer questions
and provide support. Contact NK by phone: 610.447.1555, fax: 610.447.1577, email:
info@nkhome.com, or web: www.kestrelweather.com.
5
GETTING STARTED
Pouch and Lanyards
Wrist and neck lanyards and a small pouch have been provided. To install the lanyard,
feed the thin end of the lanyard around the metal post on the battery door (as shown
in diagram). Feed the thick end of the lanyard through the loop on the thin end. Using
tweezers can help.
Battery Installation
Use only AAA batteries. Install batteries as indicated on the battery door. After installing the batteries, the
Kestrel 4250 will automatically start in the Date and Time Setting mode. (See Date and Time Setup below.)
Custom settings and chart data will be saved during a battery change; only the date/time and MMA values
will be lost.
Turning the Kestrel Meter ON and OFF
To turn the Kestrel Meter ON, press the button. To turn the Kestrel Meter OFF, hold the button for two
seconds. Or, press the button, then press the button with the word OFF highlighted. (Note: your unit
will continue to automatically store data when the power is turned o.) When rst turned on, the Kestrel
Meter will display a splash screen displaying the model number, the battery indicator, and the code version.
This battery indicator will indicate the percentage of battery life remaining, which is helpful in preventing
unexpected dead batteries.
Date and Time Setup
The rst time that you turn on your Kestrel Meter, as well as after a battery change, you will need to set the
date and time. The Introduction Screen will appear for 3 seconds, followed by the Date/
Time Setup Screen. Press the and buttons to scroll through the settings. Press the
and buttons to scroll through the setting options. After entering the date and time,
press the button to exit the Date/Time Setup. Then press the button again to exit
the Main Setup Menu.
Kestrel® 4250 Racing Weather® Tracker
7
Measurements use and
Wind Speed
Temperature
Humidity
Water Grains /Moisture
Dew Point
Station
Pressure
Density Altitude
Air
Density
Relative Air Density
Hidden Functions:
Wind Chill
Heat Index
Wet Bulb
Barometric Pressure
Altitude
See measurements section on p.14
to activate hidden functions
NAVIGATION
The Kestrel 4250 is set up to display 9 Measurements (some are
calculations) in 3 Modes.
The Measurements are listed here with their corresponding screen
icon. In addition to these Measurements and Modes, there are also 3
User Screens (one is hidden in default mode), which simultaneously
show 3 current measurements, and the Date & Time Screen. Use
the and buttons to scroll through the various Measurements,
followed by the 2 default User Screens and the Date/Time Screen. Any
of these screens can be turned o so that you can customize your
Kestrel Meter to show the screens that your application requires.
Additional measurements are available. (See the Measurements
section in the Main Menu.)
The Modes are displayed below. Use the and buttons to scroll
through the various Modes. From any mode, you may still scroll to a
dierent Measurement by pressing the and buttons.
Current - Displays the instantaneous reading.
Min/Max/Avg - Displays the Minimum/Maximum/Average readings
from stored data. If there is no stored data, the values will be displayed
as --.-.
Chart - Displays a graphical representation of up to 2000 stored data points for each measurement. If there
is no stored data, the axis will appear, but the chart will be blank. (See the following section for information
on Chart Navigation.) Modes use and
Navigation of Charts
The Kestrel 4250 is capable of storing up to 2000 data points for each measurement. To review the data, press
the button while viewing a chart. A cursor will appear on the most recent data point. Press the and
buttons to scroll through the data points. The date and time at which the data was stored will be displayed at
the bottom of the screen, and the data value will be displayed at the top of the screen. Hold down the or
button to scroll quickly through the data points.
Press the or button to review the data for the other measurements. Please note that the cursor will
remain at the same date and time. If new data is stored while viewing chart data, the entire chart will shift left
with the new data point charted on the right. The cursor will not shift with the chart.
Press the button to return to the Chart Mode.
Value
Chart
Cursor
Date & Time
Kestrel® 4250 Racing Weather® Tracker
9
SPECIAL FUNCTIONS
Customizable User Screens
The Kestrel Meter has three User Screens that can be customized to display three current
measurements simultaneously. These screens can also be turned o. (See the Main Menu
section for setup instructions.)
Max/Avg for Wind Speed & Wind Chill
The Max/Avg values for the wind speed and wind chill values are measured independently from the stored
and charted data.
This allows the user to start and stop the averaging period in the most appropriate manner for their
application. Averaging on all wind-related values (Wind Speed and Wind Chill) will be started and
stopped together.
While viewing the Min/Max/Avg screen for any of these measurements, hold the unit into the wind, and
press the button when the screen displays “--average” to begin collecting data for all measurements, and
again when the screen displays “--stop” to stop collecting data and hold the values on the display. Press the
button when the screen displays “--clear” to clear the data. This routine will work simultaneously for all
measurements, regardless of which one is displayed while the routine is run. The Max/Avg for these wind
values will not aect any other Min/Max/Avg or stored data.
Manual Data Storage
To manually store data, press the button. One of the following will appear: Data Stored (data has been
captured and will appear on chart), Full (Overwrite is o and data log is full), or O (Manual Store button has
been disabled). (See the Main Setup Menu section for more information on memory.)
Backlight
The Kestrel Meter has a high-visibility green backlight, which makes the display easily read in low-light
conditions.
Press the
button within one minute to deactivate the light manually.
Relative Humidity
The Kestrel Meter is capable of measuring RH to a high accuracy: +/– 3% RH between 5 and 95%. To ensure
operation within these specications, please follow these recommendations:
• Avoid taking measurements in direct sunlight, which will heat the air inside the humidity sensor enclosure
• If your circumstances force you to expose the Kestrel Meter to a large temperature swing prior to taking
button to activate the backlight. The light will remain activated for one minute. Press the
and cause inaccurate readings.
a relative humidity reading (such as when taking a Kestrel Meter stored inside at 70° F outside to a
temperature of 40° F), you will need to take additional steps to ensure that the Kestrel Meter’s external
temperature sensor is in thermal equilibrium.
- Ideally, provide an wind speed of at least 1 M/S (2.2 MPH), over the temperature sensor—point the
Kestrel Meter into the wind. If there is no wind, simply wave the unit back and forth so air passes
over the sensors. With airow over the temperature sensors and humidity chambers, readings within
specications will be provided within two to three minutes, even after a large temperature shift.
- If no airow can be provided, you must allow sucient time for the RH value to stabilize. This can take
as long as 20 minutes—the greater the temperature change, the greater the time. You can use the
logging capability of the Kestrel Meter to conrm that the unit has stabilized to a correct reading: Set
the memory options to a relatively short logging interval (20 seconds works well), select the graphical
Kestrel® 4250 Racing Weather® Tracker
11
display of RH, and you can see when the value is no longer changing signicantly. At that point, the RH
value is stable and can be relied upon to be within the accuracy specications.
Station Pressure, Barometric Pressure and Altitude Adjustment
The Kestrel 4250 Meter measures “station” pressure — the actual air pressure in the measurement
location. Station (Absolute) Pressure is what is shown on the “Pressure” screen. Station pressure
changes in response to two things — changes in altitude and changes in the atmosphere.
* If your racing software program asks for Station Pressure or Absolute Pressure, then use the “Pressure”
screen displayed on the Kestrel.
* If your racing software program asks for Barometric Pressure and Altitude, see below.
Barometric pressure is station pressure corrected to sea level. In order to make the correction, the Kestrel
Meter needs an accurate reference altitude. Altitude is the height above sea level. In order to correctly
calculate altitude, the unit needs an accurate barometric pressure reference, also known as an “altimeter
setting”. Fortunately, you only need to know ONE of these values (current barometric pressure or current
altitude) in order to set your Kestrel Meter up to show accurate readings.
Starting with the known barometric pressure for your location
You can obtain your current barometric pressure by checking an internet weather site for
a nearby location, or contacting a local airport. Set this value as your reference pressure
on the ALTITUDE screen to determine your correct altitude: Press the button to enter
the reference setting mode. Press the button to increase the reference pressure or the
button to decrease the reference pressure. You will notice that the altitude will change with changes in
the reference pressure. Press the button to exit the adjustment mode. Set your Kestrel Meter down on a
table and allow the altitude reading to stabilize. (Note: very small changes in pressure generate noticeable
changes in altitude. In order to provide meaningful readings for activities where altitude changes quickly,
the Kestrel Meter features rapid altitude response. This is why the altitude readings tend to uctuate by a
few feet.) After obtaining a current altitude from the ALTITUDE screen, move to the BARO screen and enter
this value as your reference altitude by following the same procedure. Both readings will now be accurate.
Starting with a known altitude for your location
You can obtain your altitude from a topographical map or local landmark. Google Earth
is an excellent free program that provides the exact altitude for any given address: www.
earth.google.com/. Set this value as your reference altitude on the BARO screen to
determine your barometric pressure: Press the button to enter the reference setting mode. Press the
button to increase the reference altitude or the button to decrease the reference altitude. You will notice
that the barometric pressure will change with changes in the reference altitude. Press the button to exit
the adjustment mode. Again, allow the Kestrel Meter to stabilize, then enter the value from the BARO screen
as your reference pressure on the ALTITUDE screen by following the same procedure. Both readings are now
accurate.
When reviewing stored data, remember that changes in pressure AND changes in location/altitude will aect
the stored values. When tracking pressure changes relative to weather, set the reference altitude on the BARO
screen and keep the Kestrel Meter in one location. Your graph history will now show trends in barometric
pressure. Your altitude as shown on the ALTITUDE screen will change as the weather changes, but you can
ignore this screen for this purpose.
If you are planning a day hike would like to track your altitude, you’ll need to enter the correct reference
pressure on the ALTITUDE screen as described above in “starting with the known barometric pressure.”
You can now track the altitude changes as you hike. In this instance, you should ignore the values on the
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