Apogee SF-110 User manual

APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA
TEL: [phone] | FAX: [phone] | WEB: APOGEEINSTRUMENTS.COM
Copyright © 2018 Apogee Instruments, Inc.
OWNER’S MANUAL
RADIATION FROST DETECTOR
Model SF-110
Turfschipper 114 | 2292 JB Wateringen | Tel. [phone] | www.catec.nl | [e-mail] 114 | 2292 JB Wateringen | Tel. [phone] | www.catec.nl | [e-mail]
MEE T I NST RUME N TATI E

TABLE OF CONTENTS
Owner’s Manual ............................................................................................................................................................................... 1
Certificate of Compliance......................................................................................................................................................... 3
Introduction ............................................................................................................................................................................. 4
Sensor Models ......................................................................................................................................................................... 5
Specifications ........................................................................................................................................................................... 6
Deployment and Installation.................................................................................................................................................... 7
Cable Connectors..................................................................................................................................................................... 8
Operation and Measurement .................................................................................................................................................. 9
Maintenance and Recalibration............................................................................................................................................. 11
Troubleshooting and Customer Support................................................................................................................................ 12
Return and Warranty Policy................................................................................................................................................... 13

CERTIFICATE OF COMPLIANCE
EU Declaration of Conformity
This declaration of conformity is issued under the sole responsibility of the manufacturer:
Apogee Instruments, Inc.
721 W 1800 N
Logan, Utah 84321
USA
for the following product(s):
Models: SF-110
Type: Radiation Frost Detector
The object of the declaration described above is in conformity with the relevant Union harmonization legislation:
2014/30/EU Electromagnetic Compatibility (EMC) Directive
2011/65/EU Restriction of Hazardous Substances (RoHS 2) Directive
Standards referenced during compliance assessment:
EN 61326-1:2013 Electrical equipment for measurement, control and laboratory use –EMC requirements
EN 50581:2012 Technical documentation for the assessment of electrical and electronic products with respect to
the restriction of hazardous substances
Please be advised that based on the information available to us from our raw material suppliers, the products
manufactured by us do not contain, as intentional additives, any of the restricted materials including cadmium,
hexavalent chromium, lead, mercury, polybrominated biphenyls (PBB), polybrominated diphenyls (PBDE).
Further note that Apogee Instruments does not specifically run any analysis on our raw materials or end products
for the presence of these substances, but rely on the information provided to us by our material suppliers.
Signed for and on behalf of:
Apogee Instruments, May 2018
Bruce Bugbee
President
Apogee Instruments, Inc.

INTRODUCTION
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 (see figure on following page). 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.
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 predictor 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 analog 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.
Simulated leaf (green trace in top panel) and bud (blue trace in top panel) temperatures from an Apogee
model SF-110 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.

SENSOR MODELS
SF-110 radiation frost detectors use the same precision thermistors as Apogee ST series thermistor temperature
sensors, but with the thermistors mounted into a simulated leaf and a simulated bud. SF-110 detectors are rugged
and weatherproof, and are designed to be exposed to ambient environmental conditions.
Sensor model number and serial number are
located on a label near the pigtail lead wires. If
you need the manufacturing date of your sensor,
please contact Apogee Instruments with the
serial number of your sensor.

SPECIFICATIONS
SF-110
Measurement Range
-50 to 70 C
Measurement Uncertainty
0.1 (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
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)
Equilibration Time
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)
Operating Environment
-50 to 70 C; 0 to 100 % relative humidity
Meter Dimension
126 mm length, 70 mm width, 24 mm height
Input Voltage Requirement
2.5 V DC excitation (recommended, see Operation and Measurement section)
Output Voltage
Requirement
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)
Dimensions
570 mm length, 21 mm pipe diameter, 70 mm disk diameter (see diagram below)
Mass
400 g
Cable
5 m of four conductor, shielded, twisted-pair wire; additional cable available in multiples of 5 m; TPR jacket
(high water resistance, high UV stability, flexibility in cold conditions); pigtail lead wires

DEPLOYMENT AND INSTALLATION
Apogee SF-110 radiation frost detectors should be mounted in within, or very near, the plant canopy where frost
detection is desired, so that the simulated leaf and bud are in the same environment as actual leaves and buds.
An Apogee Instruments model AM-210 mounting bracket can be used to mount the detector to a cross arm or
pole. The AM-210 allows adjustment of the angle of the detector. Mounting the detector with a slight downward
slope, or tilt to one side, is recommended to minimize moisture/debris build-up on the simulated leaf.

CABLE CONNECTORS
Apogee started offering in-line cable connectors on
some bare-lead sensors in March 2018 to simplify the
process of removing sensors from weather stations for
calibration (the entire cable does not have to be
removed from the station and shipped with the sensor).
The ruggedized M8 connectors are rated IP68, made of
corrosion-resistant marine-grade stainless-steel, and
designed for extended use in harsh environmental
conditions.
Inline cable connectors are installed 30 cm from the
head
(pyranometer pictured)
Instructions
Pins and Wiring Colors: All Apogee connectors have six
pins, but not all pins are used for every sensor. There
may also be unused wire colors inside the cable. To
simplify datalogger connection, we remove the unused
pigtail lead colors at the datalogger end of the cable.
If you ever need a replacement cable, please contact us
directly to ensure ordering the proper pigtail
configuration.
Alignment: When reconnecting your sensor, arrows on
the connector jacket and an aligning notch ensure
proper orientation.
Disconnection for extended periods: When
disconnecting the sensor for an extended period of time
from a station, protect the remaining half of the
connector still on the station from water and dirt with
electrical tape or other method.
A reference notch inside the connector ensures
proper alignment before tightening.
When sending sensors in for calibration, only send the
short end of the cable and half the connector.
Tightening: Connectors are designed to be firmly
finger-tightened only. There is an O-ring inside the
connector that can be overly compressed if a wrench is
used. Pay attention to thread alignment to avoid cross-
threading. When fully tightened, 1-2 threads may still
be visible.
Finger-tighten firmly

OPERATION AND MEASUREMENT
Connect the detector to a measurement device (meter, datalogger, controller) capable of inputting 2.5 V DC, and
measuring and displaying or recording two millivolt (mV) signals (an input measurement range of 0 to 2500 mV is
required to cover the entire temperature range of the detector). In order to maximize measurement resolution
and signal-to-noise ratio, the input range of the measurement device should closely match the output range of the
thermistors.
VERY IMPORTANT: Apogee changed all wiring colors of our bare-lead sensors in March 2018. To ensure
proper connection to your data device, please note your serial number then use the appropriate wiring
configuration below.
Wiring for SF-110 Serial Numbers range 0-1137
Red: Excitation channel (excitation for leaf thermistor)
Black: Single-ended channel (positive leaf thermistor lead)
Blue: Analog ground (negative leaf thermistor lead)
Clear: Analog ground (shield wire)
White: Excitation channel (excitation for bud thermistor)
Green: Single-ended channel (positive bud thermistor lead)
Orange: Analog ground (negative bud thermistor lead)
Red: Excitation channel (excitation for leaf and bud
thermistor)
Black: Therm 1 (negative leaf thermistor lead)
Clear: Shield/Ground
Green: Therm 2 (positive bud thermistor lead)
Blue: Therm 2 (negative bud thermistor lead)
White: Therm 1 (positive leaf thermistor lead)

Measurement devices (e.g., datalogger, controller) do not measure resistance directly, but determine resistance
from a half-bridge measurement, where an excitation voltage is input across the thermistor and an output voltage
is measured across the bridge resistor (circuit diagram shown below is for simulated leaf thermistor, but the circuit
for the simulated bud thermistor is the same, where Red = Red, White = Green, Black = Blue).
An excitation voltage of 2.5 V DC is recommended to minimize self-heating and current drain, while still
maintaining adequate measurement sensitivity (mV output from thermistor per C). However, other excitation
voltages can be used. Decreasing the excitation voltage will decrease self-heating and current drain, but will also
decrease thermistor measurement sensitivity. Increasing the excitation voltage will increase thermistor
measurement sensitivity, but will also increase self-heating and current drain.
Conversion of Thermistor Resistance to Temperature
The thermistors in the simulated leaf and bud have a resistive element where resistance changes with
temperature. Thermistor resistance (RT, in Ω) is measured with a half-bridge measurement, requiring an excitation
voltage input (VEX) and a measurement of output voltage (VOUT):







 1
V
V
24900R
OUT
EX
T
(1)
where 24900 is the resistance of the bridge resistor in Ω. From resistance, temperature (TK, in Kelvin) is calculated
with the Steinhart-Hart equation and thermistor specific coefficients:
3
TT
K))R(ln(C)Rln(BA 1
T 
(2)
where A = 1.129241 x 10-3, B = 2.341077 x 10-4, and C = 8.775468 x 10-8 (Steinhart-Hart coefficients). If desired,
measured temperature in Kelvin can be converted to Celsius (TC):
15.273TT KC 
(3)