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

Apogee SF-110 Frost Sensor

The SF-110 Frost Sensor 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-110 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-110 is -40 to +70°C with an accuracy of ± 0.1°C from 0 to +70°C

SF-110 Frost Sensor Features

The SF-110 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-110 provides close approximations to leaf and bud temperatures and can be used for prediction of frost on leaves and buds.

On clear, calm nights, leaf and bud temperature can drop below freezing even if air temperature remains slightly 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 clear sky). Under cloudy and/or windy conditions, radiation frost events do not occur.

The temperature measurement range of the SF-110 is -40 to +70°C with an accuracy of ± 0.1°C from 0 to +70°C. However, the sensor is intended for applications in crop 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: < 0.05°C
Non-stability (Long-term Drift): < 0.02°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
Self-Heating: < 0.01°C (typical, assuming pulsed excitation of 2.5 V DC), 0.08°C at 5°C (maximum, assuming continuous input excitation of 2.5 V DC)
Operating Environment: -50 to 70°C, 0 to 100% relative humidity
Input Voltage Requirement: 2.5 V DC excitation (recommended, see Operation and Measurement section)
Output Voltage Range: 0 to 2.5 V DC (assuming input excitation of 2.5 V DC)
Current Drain: 0.1 mA DC (per thermistor) at 70°C (maximum, assuming continuous input excitation of 2.5 V DC)
Dimensions: 57 cm length, 2.1 cm pipe diameter, 7.0 cm disk diameter
Mass: 400g
Cable: 5m of 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 wire.

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 long wave radiation balance at the surface (more longwave radiation is being emitted from the surface than what the surface is absorbing from the clear sky). Under cloudy and/or windy conditions, radiation frost events do not occur.

Apogee model SF-110 radiation frost detectors are designed to approximate plant leaf and flower bud temperatures for prediction of frost events. SF-110 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 predict or of frost formation. Apogee Instruments SF-110 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-110 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-110 detectors output two analogue voltage signals (when supplied with input voltages) that are related to the resistances of independent thermistors. Resistances are directly related to simulated leaf and bud temperatures.