Leaf and Bud Temperature Sensor

  • Model: E-804-SF-110-SS/E804-SF-421-SS
  • Manufactured by: Apogee


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Product Description:

Provides on-site, real-time warning of radiation frost events

Apogee Instruments’ leaf and bud temperature sensor (formerly called the radiation frost detector) is an innovative temperature sensor designed to mimic leaves and flower/fruit buds, which can sometimes drop well below the ambient air temperature due to long-wave radiation loss on clear, calm nights. Knowing exactly when a radiation frost even is occurring allows you to activate frost protection equipment in time to protect your crops and eliminates starting frost protection too early, which wastes money.

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.

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.

  SF-110 SF-421
Measurement Range -50 to 70 C -50 to 70 C
Measurement Uncertainty 0.1 C (from 0 to 70 C), 0.2 C (from -25 to 0 C), 0.4 (from -50 to -25 C) 0.1 C (from 0 to 70 C), 0.2 C (from -25 to 0 C), 0.4 (from -50 to -25 C)
Measurement Repeatability Less than 0.05 C Less than 0.05 C
Long-term Drift (Non-stability) Less than 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) Less than 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 10 s 10 s
Self-heating Less than 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) Less than 0.01 C
Operating Environment -50 to 70 C; 0 to 100 % relative humidity -50 to 70 C; 0 to 100 % relative humidity
Input Voltage Requirement 2.5 V DC excitation 5.5 to 24 V DC
Output Voltage Range 0 to 2.5 V DC (assuming input excitation of 2.5 V DC) -
Current Draw 0.1 mA DC (per thermistor) at 70 C (maximum, assuming continuous input excitation of 2.5 V DC) 0.6 mA (quiescent), 1.3 mA (active)
Dimensions 570 mm length, 21 mm pipe diameter, 70 mm disk diameter 570 mm length, 21 mm pipe diameter, 70 mm disk diameter
Mass 400g 400g