So how cold can you really use your Kestrel Meter?
In looking at the spec sheet, it's cause for some confusion.... It reads 3 different temperature specs! With a recent call from an honorable armed forces guy up in the extremes of Alaska wondering if he could get a reading at 50 below, to essentially set up a portable weather station, I decided to write out some clarification....
The spec sheet 3 temperature definitions:
°F -49.0 to 257.0 °F
°C -45.0 to 125.0 °C
Measures air, water and snow temperature. Thermally isolated, hermetically sealed, precision thermistor mounted externally (US Patent 5,939,645). Calibration drift negligible
Operational Temperature Range (LCD and Batteries)
The operational temperature range of the liquid crystal display and batteries is
°F 14° F to 131 ° F
°C -10°C to 55 °C
Beyond the limits of the operational temperature range, the unit must be maintained within range and exposed for minimum time necessary to take reading.
Storage Temperature All Models
°F -22 °F to 140 °F
°C -30 °C to 60 °C
The short answer:
It will absolutely work, but he can't just leave it outside and expect to walk out on the hour and check it.
The long answer and why:
The operational range is the first section above– the Kestrel can operate within that range (or at least, should be able to operate without compromising the unit), the second section is the range at which the LCD will operate, under 14 F the screen will fade out and over 130ish °F the screen will go completely black (this is a function of all liquid crystal displays). However, if you keep your Kestrel in a place where it is between 14 and 131 F just before exposing it to the temperatures outside of that range that you’d like to measure, it is still possible to obtain measurements. For example, in winter of 2010 we talked with a person from northern Alaska who would keep his Kestrel in his pocket until he wanted to take a reading, then pull it out and wave it around to promote airflow over the sensors and allow the Kestrel to acclimate much more quickly, and he was quite happy with the Kestrel. He mentioned his readings were -40 or -50 degrees or so. The storage temperatures there are probably much more liberal than I would recommend – I would probably recommend keeping it above 15F and below 100F if possible – It would not make much sense to store a Kestrel below the point at which the display stops working for a considerable period of time.