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Apogee Instruments' radiation frost detector is a unique temperature sensor designed to mimic leaves and flower/fruit buds, rather than measure air temperature.


Monitor Radiation Frost Events
On calm, clear nights surface temperature, including leaf and bud temperatures, can drop well below air temperature due to a net loss of longwave radiation to the clear sky. A radiation frost occurs when frost forms at the surface before the air temperature reaches freezing (0 C). Under cloudy and/or windy conditions, radiation frost events do not occur. The Apogee radiation frost detector is a combination of two high accuracy thermistors mounted in a single housing. One sensor is designed to mimic a leaf and sensor is designed to mimic a bud, providing estimates of leaf and bud temperatures and a direct means of monitoring radiation frost events.



Leaf and bud temperature approximations measured with an Apogee SF-110 compared to air temperature (top panel) and wind speed (bottom panel) on the evening of April 28, 2012. Leaf and bud temperatures were both below air temperature after 8 P.M. and reached freezing 6 (leaf) and 4 (bud) hours before the air temperature.


Wide Range, Accurate Measurements
Thermistor accuracy is ± 0.1 C across a range of 0 to 70 C, providing accurate measurements at temperatures near zero where frost damage is likely to occur.


Typical Applications
Applications include leaf and bud temperature estimates in cropped fields, orchards, and vineyards. Leaf and bud temperatures returned by the detector can then be used to alert growers to the potential of frost damage to crops.


Output Options
Analog and digital output options are available. Analog version is an un-amplified voltage output. Digital version is SDI-12 communication protocol.


The AM-220 mounting bracket is designed to orient sensors at varying angles to satisfy all applications. The bracket can be mounted to a mast or pipe, while the sensor bracket will accommodate the sensor.

Warranty and Support
All Apogee products are backed by an industry-leading four year warranty and outstanding customer support.


Need help choosing a sensor?

  Technical Information
Technical Information
Find knowledge base articles, manuals, FAQs, technical support, and more.
+ Which radiation frost detector model do I need?
All radiation frost detectors use the same thermistor. The model number you need depends on which output is compatible with your datalogger. Model numbers are listed below with their output.
SF-110 Analog 0 to 2.5 V
SF-410 Digital SDI-12 Communication Protocol

spec sheets
Specification Sheets




Lecture 6-Radiation Frost