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Enabling better global research outcomes in soil, plant & environmental monitoring.

SF-410: SDI-12 Radiation Frost Detector

The SF-410 is a combination of two temperature sensors (precision thermistors) in a single housing. One sensor is designed to mimic a plant leaf and the other a flower bud. The SF-410 provides close approximations to leaf and bud temperatures and can be used for prediction of frost on leaves and buds.

The temperature measurement range of the SF-410 is -50 to +70°C with an accuracy of ± 0.1°C from 0 to +70°C. However, the sensor is intended for applications in cropped fields and orchards when temperatures will be near freezing, and where air temperature measurements are not a good predictor of frost formation.

Measurement Range -50 to 70°C
Measurement Uncertainty 0.1°C (from 0 to 70°C);
0.2°C (from -25 to 0°C);
0.4°C (from -50 to -25°C)
Measurement Repeatability Less than 0.05°C
Non-Stability
Long-Term Drift
Less than 0.2°C per year (when used in non-condensing environments where the annual average temperature is less than 30°C; continuously high temperatures or continuously humid environments increase drift rate)
Equilibration time 10s
Response Time Fastest data transmission rate for SDI-12 circuitry is 1s.
Self-Heating Less than 0.01
Operating Environment -50 to 70°C; 0 to 100% Relative Humidity
Input Voltage Requirement 4.5 to 24 V DC
Current Drain 0.6 mA (quiescent); 1.3mA (active).
Dimensions 57cm length; 2.1cm pipe diameter; 7.0cm disk diameter.
Mass 400g
Cable 5m of two conductor, shielded, twisted-pair wire; additional cable available in multiples of 5m; santoprene rubber jacket (high water resistance, high UV stability, flexibility in cold conditions); pigtail lead wires

SF-410 Dimensions

Frost damage to plants can have large impacts on crop yield and quality. Protection of crops during frost events is dependent on the accuracy of plant temperature predictions. Often, air temperature is not a reliable predictor of timing, duration and severity of frost events because plant canopy temperatures can be significantly different than air temperature under certain environmental conditions.

On clear, calm nights, plant leaf and flower bud temperatures can drop below freezing even if air temperature remains above 0°C. This is called a radiation frost and is due to the lack of air mixing (wind) near the surface, and a negative net longwave radiation balance at the surface (more longwave radiation is being emitted from the surface than what the surface is absorbing from the lear sky. Under cloudy and/or windy conditions, radiation frost events do not occur.

Apogee model SF-410 radiation frost detectors are designed to approximate plant leaf and flower bud temperatures for prediction of frost events. SF-410 radiation frost detectors are intended for applications in cropped fields and orchards when air temperatures will be near freezing, and where air temperature measurements are not a good predictor of frost formation.

Apogee Instruments SF-410 radiation frost detectors consist of two precision thermistors, one combined with a simulated leaf and the other a simulated bud, in a single housing. The leaf sensor is designed to mimic a plant leaf and the bud sensor is designed to mimic a flower bud. SF-410 radiation frost detectors provide close approximations to leaf and bud temperatures and can be used for prediction of frost on leaves and buds. Detectors are weatherproof and are designed for continuous temperature measurement in the same environmental conditions plants are exposed to. SF-410 detectors output both the leaf and bud temperatures in SDI-12 format.

SF-410 Response

Simulated leaf (green trace in top panel) and bud (blue trace in top panel) temperatures from an Apogee model SF-410 radiation frost detector compared to air temperature (black trace in top panel) during a clear (net longwave radiation is plotted in middle panel), calm (wind speed is plotted in bottom panel) night during spring in Logan, Utah. Simulated leaf and bud temperatures reached the freezing point approximately 5.5 and 3.0 hours before air temperature, respectively.