This is a pretty popular question! As the Kestrel specification sheet shows, the temperature sensor limits for Kestrel Meter’s is -20.0 to 158.0 °F | -29.0 to 70.0 °C. The operational range for Kestrel Meters is 14° F to 131° F | -10 °C to 55 °C. The operational range is where the Meter’s LCD screen is guaranteed to function properly. As with all LCD displays, they do not like long term exposures to extremely cold temperatures as the LCD display will start to slow down and eventually white out. Many of our customers use their meters outside of the operational range to take readings within the specification range though. 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 then exposing it to the more extreme environment for the minimum time necessary to take readings. Basically, If you wish to take a temperature reading when it is extremely cold outside, keep the meter with you inside your dwelling or keep the meter on you if you are outside like in your jacket pocket. When ready to take your temperature reading, take the meter out and swing it around a little until the temperature stabilizes or if it’s windy, just hold the meter in the wind until the temperature stabilizes (See how to take accurate readings below). Then put the meter back in its happy place until you are ready to take the next reading. Just to prove a point, as you can see in the pictures, we placed a Kestrel 5500 meter with Bluetooth (LiNK) in a bowl full of water and placed it in a freezer for 24 hours. We were able to take temperature readings real-time while the meter was frozen in a block of ice at zero degrees Fahrenheit using an iPhone with the Kestrel LiNK app. We were also able to download data results from its entire time in the freezer. We could barely see the LCD display on the meter as it was covered by ice but we could see the display was on and functioning. While the Kestrel held up perfectly, we do not recommend freezing your Kestrel in a block of ice.
Special note: The temperature operational range was originally developed using the older Kestrel 4 series meters. The newer 5 series meters screen is more advanced and durable and we believe can be left in colder temperatures and function properly. We will test this theory during the winter of 2016-2017.
How to take an accurate temperature reading with my Kestrel
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.