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)

MAINTENANCE AND RECALIBRATION
Apogee SF-110 radiation frost detectors are weatherproof and are designed to be continuously deployed in
outdoor conditions. When detectors are not is use, it is recommended that they be removed from the
measurement environment, cleaned, and stored. SF-110 detectors deployed in the field should be periodically
cleaned to remove all dust and debris.
Thermistors in SF-110 detectors are not factory calibrated, but come with a generic calibration (see Steinhart-Hart
coefficients in OPERATION AND MEASUREMENT section). A custom calibration can be derived by comparing the
temperature from the simulated leaf and bud thermistors to a reference temperature measurement. Often, a
simple offset can be used to make the measured temperature match the reference temperature.

TROUBLESHOOTING AND CUSTOMER SUPPORT
Independent Verification of Functionality
Apogee SF-110 radiation frost detectors yield two independent resistances that are proportional to simulated leaf
and bud temperatures. A quick and easy check of functionality of the two thermistors can be accomplished with an
ohmmeter.
To check the simulated leaf circuit, connect the lead wires of the ohmmeter to the red and white wires from the
detector. The resistance should read 10 kΩ(10,000 ohms) at 25 C. If detector temperature is less than 25 C,
resistance will be higher. If detector temperature is greater than 25 C, resistance will be lower. Connect the lead
wires of the ohmmeter to the white and black wires from the detector. The resistance should read 24.9 kΩ, and
should not vary. Connect the lead wires of the ohmmeter to the red and black wires from the sensor. The
resistance should be the sum of the resistances measured across the red and white wires, and white and black
wires (e.g., 10 kΩplus 24.9 kΩat 25 C).
To check the simulated bud circuit, connect the lead wires of the ohmmeter to the red and green wires from the
sensor. The resistance should read 10 kΩat 25 C. If detector temperature is less than 25 C, resistance will be
higher. If detector temperature is greater than 25 C, resistance will be lower. Connect the lead wires of the
ohmmeter to the green and blue wires from the detector. The resistance should read 24.9 kΩ, and should not vary.
Connect the lead wires of the ohmmeter to the red and blue wires from the sensor. The resistance should be the
sum of the resistances measured across the red and green wires, and green and blue wires (e.g., 10 kΩplus 24.9
kΩat 25 C).
Compatible Measurement Devices (Dataloggers/Controllers/Meters)
Measurement of thermistor resistance requires an input excitation voltage, where 2.5 V DC is recommended. A
compatible measurement device should have the capability to supply the necessary voltage.
The sensitivity (mV output from thermistor per C) of the temperature measurements vary with the excitation
voltage, and vary as a function of temperature. With an excitation voltage of 2.5 V DC, the sensitivity is lowest near
the ends of the measurement range, -50 and 70 C. A compatible measurement device (e.g., datalogger or
controller) should have resolution of at least 0.6 mV, in order to produce temperature resolution of less than 0.1 C
across the entire temperature measurement range (less than 0.05 C from -35 to 45 C).
An example datalogger program for Campbell Scientific dataloggers can be found on the Apogee webpage at
http://www.apogeeinstruments.com/content/Radiation-Frost-Detection-Sensor.CR1.
Modifying Cable Length
When the detector is connected to a measurement device with high input impedance, detector output signals are
not changed by splicing on additional cable in the field. Tests have shown that if the input impedance of the
measurements device is 1 mega-ohm or higher then there is negligible effect on the SF-110 radiation frost
detector, even after adding up to 100 m of cable. See Apogee webpage for details on how to extend sensor cable
length (http://www.apogeeinstruments.com/how-to-make-a-weatherproof-cable-splice/). For cable extensions,
shielded, twisted pair cable is recommended, in order to minimize electromagnetic interference. This is particularly
important for long lead lengths in electromagnetically noisy environments.
The precision bridge resistors are located at the pigtail end of the cable. Thus, the SF-110 cable should not be
shortened, otherwise the bridge resistor will be removed.

RETURN AND WARRANTY POLICY
RETURN POLICY
Apogee Instruments will accept returns within 30 days of purchase as long as the product is in new condition (to be
determined by Apogee). Returns are subject to a 10 % restocking fee.
WARRANTY POLICY
What is Covered
All products manufactured by Apogee Instruments are warranted to be free from defects in materials and
craftsmanship for a period of four (4) years from the date of shipment from our factory. To be considered for
warranty coverage an item must be evaluated either at our factory or by an authorized distributor.
Products not manufactured by Apogee (spectroradiometers, chlorophyll content meters) are covered for a period
of one (1) year.
What is Not Covered
The customer is responsible for all costs associated with the removal, reinstallation, and shipping of suspected
warranty items to our factory.
The warranty does not cover equipment that has been damaged due to the following conditions:
1. Improper installation or abuse.
2. Operation of the instrument outside of its specified operating range.
3. Natural occurrences such as lightning, fire, etc.
4. Unauthorized modification.
5. Improper or unauthorized repair.
Please note that nominal accuracy drift is normal over time. Routine recalibration of sensors/meters is considered
part of proper maintenance and is not covered under warranty.
Who is Covered
This warranty covers the original purchaser of the product or other party who may own it during the warranty
period.
What We Will Do
At no charge we will:
1. Either repair or replace (at our discretion) the item under warranty.
2. Ship the item back to the customer by the carrier of our choice.
Different or expedited shipping methods will be at the customer’s expense.

How To Return An Item
1. Please do not send any products back to Apogee Instruments until you have received a Return Merchandise
Authorization (RMA) number from our technical support department by calling [phone] or by submitting an
online RMA form at www.apogeeinstruments.com/tech-support-recalibration-repairs/. We will use your RMA
number for tracking of the service item.
2. Send all RMA sensors and meters back in the following condition: Clean the sensor’s exterior and cord. Do not
modify the sensors or wires, including splicing, cutting wire leads, etc. If a connector has been attached to the
cable end, please include the mating connector –otherwise the sensor connector will be removed in order to
complete the repair/recalibration.
3. Please write the RMA number on the outside of the shipping container.
4. Return the item with freight pre-paid and fully insured to our factory address shown below. We are not
responsible for any costs associated with the transportation of products across international borders.
5. Upon receipt, Apogee Instruments will determine the cause of failure. If the product is found to be defective in
terms of operation to the published specifications due to a failure of product materials or craftsmanship, Apogee
Instruments will repair or replace the items free of charge. If it is determined that your product is not covered
under warranty, you will be informed and given an estimated repair/replacement cost.
Apogee Instruments, Inc.
721 West 1800 North Logan, UT
84321, USA
OTHER TERMS
The available remedy of defects under this warranty is for the repair or replacement of the original product, and
Apogee Instruments is not responsible for any direct, indirect, incidental, or consequential damages, including but
not limited to loss of income, loss of revenue, loss of profit, loss of wages, loss of time, loss of sales, accruement of
debts or expenses, injury to personal property, or injury to any person or any other type of damage or loss.
This limited warranty and any disputes arising out of or in connection with this limited warranty ("Disputes") shall
be governed by the laws of the State of Utah, USA, excluding conflicts of law principles and excluding the
Convention for the International Sale of Goods. The courts located in the State of Utah, USA, shall have exclusive
jurisdiction over any Disputes.
This limited warranty gives you specific legal rights, and you may also have other rights, which vary from state to
state and jurisdiction to jurisdiction, and which shall not be affected by this limited warranty. This warranty
extends only to you and cannot by transferred or assigned. If any provision of this limited warranty is unlawful,
void or unenforceable, that provision shall be deemed severable and shall not affect any remaining provisions. In
case of any inconsistency between the English and other versions of this limited warranty, the English version shall
prevail.
This warranty cannot be changed, assumed, or amended by any other person or agreement.
APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA
TEL: [phone] | FAX: [phone] | WEB: APOGEEINSTRUMENTS.COM
Copyright © 2018 Apogee Instruments, Inc.