Apogee Instruments SQ-642 User manual

APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA
TEL: [phone] | FAX: [phone] | WEB: APOGEEINSTRUMENTS.COM
Copyright © 2021 Apogee Instruments, Inc.
OWNER’S MANUAL
QUANTUM LIGHT POLLUTION
SENSOR
Models SQ-642 and SQ-645
Rev: 4-Oct-2021

TABLE OF CONTENTS
Owner’s Manual ............................................................................................................................................................................... 1
Certificate of Compliance......................................................................................................................................................... 3
Introduction ............................................................................................................................................................................. 4
Sensor Models ......................................................................................................................................................................... 5
Specifications ........................................................................................................................................................................... 6
Deployment and Installation.................................................................................................................................................... 8
Cable Connectors..................................................................................................................................................................... 9
Operation and Measurement ................................................................................................................................................ 10
Maintenance and Recalibration............................................................................................................................................. 13
Troubleshooting and Customer Support................................................................................................................................ 14
Return and Warranty Policy................................................................................................................................................... 15

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: SQ-642, SQ-645
Type: Quantum Light Pollution Sensor
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
2015/863/EU Amending Annex II to Directive 2011/65/EU (RoHS 3)
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 lead (see
note below), mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), polybrominated
diphenyls (PBDE), bis (2-ethylhexyl) phthalate (DEHP), butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), and
diisobutyl phthalate (DIBP). However, please note that articles containing greater than 0.1% lead concentration are
RoHS 3 compliant using exemption 6c.
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 we rely on the information provided to us by our material suppliers.
Signed for and on behalf of:
Apogee Instruments, October 2021
Bruce Bugbee
President
Apogee Instruments, Inc.

INTRODUCTION
Radiation that drives photosynthesis is called photosynthetically active radiation (PAR) and is typically defined as
total radiation across a range of 400 to 700 nm. PAR is almost universally quantified as photosynthetic photon flux
density (PPFD) in units of micromoles per square meter per second (µmol m-2 s-1, equal to microEinsteins per
square meter per second) summed from 400 to 700 nm (total number of photons from 400 to 700 nm). However,
Ultraviolet and far-red photons outside the defined PAR range of 400-700 nm can also contribute to
photosynthesis and influence plant responses (e.g., flowering).
Sensors that measure PPFD are often called quantum sensors due to the quantized nature of radiation. A quantum
refers to the minimum quantity of radiation, one photon, involved in physical interactions (e.g., absorption by
photosynthetic pigments). In other words, one photon is a single quantum of radiation. Sensors that function like
traditional quantum sensors but measure a wider range of wavelengths can be thought of as an ‘extended range’
quantum sensor.
Typical applications of traditional quantum sensors include incoming PPFD measurement over plant canopies in
outdoor environments or in greenhouses and growth chambers and reflected or under-canopy (transmitted) PPFD
measurement in the same environments. The Extended Range PFD Sensor detailed in this manual uses a detector
that is sensitive to radiation up to about 1100 nm, well beyond the range of wavelengths that influence
photosynthesis and plant responses. This means this particular sensor should only be used for photon flux
density measurements under LEDs.
Apogee Instruments SQ-600 series Quantum Light Pollution Sensors consist of a cast acrylic diffuser (filter),
photodiode, and signal processing circuitry mounted in an anodized aluminum housing, and a cable to connect the
sensor to a measurement device. SQ-600 series sensors are designed for continuous photon flux density
measurements in indoor environments under LEDs. The SQ-640 Quantum Light Pollution models output a voltage
that is directly proportional to photon flux density. The voltage output by the sensor is directly proportional to
radiation incident on a planar surface (does not have to be horizontal), where the radiation emanates from all
angles of a hemisphere.

SENSOR MODELS
This manual covers the amplified voltage output models SQ-642 and SQ-645 Quantum Light Pollution Sensor (in
bold below). Additional models are covered in their respective manuals.
Model
Signal
SQ-640
Self-powered
SQ-642
0-2.5 V
SQ-644
4-20 mA
SQ-645
0-5 V
SQ-646
USB
SQ-647
SDI-12
SQ-648
Modbus
A sensor’s model number and serial number are
located on the bottom of the sensor. If the
manufacturing date of a specific sensor is
required, please contact Apogee Instruments
with the serial number of the sensor.

SPECIFICATIONS
Calibration Traceability
Apogee Instruments SQ-600 series quantum light pollution sensors are calibrated through side-by-side comparison
to the mean of four transfer standard quantum light pollution sensors under a reference lamp. The transfer
standard quantum light pollution sensors are recalibrated with a quartz halogen lamp traceable to the National
Institute of Standards and Technology (NIST).
SQ-642-SS
SQ-645-SS
Power Supply
5 to 24 V DC
5.5 to 24 V DC
Current Draw
12 V is 57 µA
Sensitivity
12.5 mV per µmol m-2 s-1
25 mV per µmol m-2 s-1
Calibration Factor
0.08 µmol m-2 s-1 per mV
0.04 µmol m-2 s-1 per mV
Calibration
Uncertainty
± 5 % (see Calibration Traceability below)
Output Range
0 to 2.5 V
0 to 5 V
Measurement
Range
0 to 200 µmol m-2 s-1
Measurement
Repeatability
Less than 0.5 %
Long-term Drift
(Non-stability)
Less than 2 % per year
Non-linearity
Less than 1 % (up to 200 µmol m-2 s-1)
Response Time
Less than 1 ms
Field of View
180°
Spectral Range
340 to 1040 nm ± 5 nm (wavelengths where response is greater than 50 %; see Spectral Response
below)
Directional
(Cosine) Response
± 2 % at 45° zenith angle, ± 5 % at 75° zenith angle (see Directional Response below)
Azimuth Error
Less than 0.5 %
Tilt Error
Less than 0.5 %
Temperature
Response
-0.11 ± 0.04 % per C
Uncertainty in
Daily Total
Less than 5 %
Housing
Anodized aluminum body with acrylic diffuser
IP Rating
IP68
Operating
Environment
-40 to 70 C; 0 to 100 % relative humidity; can be submerged in water up to depths of 30 m
Dimensions
30.5 mm diameter, 37 mm height
Mass (with 5 m of
cable)
140 g
Cable
5 m of two conductor, shielded, twisted-pair wire; TPR jacket; pigtail lead wires; stainless steel (316),
M8 connector
Warranty
4 years against defects in materials and workmanship

Spectral Response
Cosine Response
Directional, or cosine, response is defined as the
measurement error at a specific angle of radiation
incidence. Error for Apogee SQ-600 series Quantum Light
Pollution Sensor is approximately ± 2 % and ± 5 % at solar
zenith angles of 45° and 75°, respectively.
Mean spectral response measurements of
six replicate Apogee SQ-600 series Quantum
Light Pollution Sensors. Spectral response
measurements were made at 10 nm
increments across a wavelength range of
300 to 1100 nm in a monochromator with
an attached electric light source. Measured
spectral data from each quantum light
pollution sensor were normalized by the
measured spectral response of the
monochromator/electric light combination,
which was measured with a
spectroradiometer

DEPLOYMENT AND INSTALLATION
Mount the sensor to a solid surface with the nylon mounting screw provided. To accurately measure photon flux
density incident on a horizontal surface, the sensor must be level. An Apogee Instruments model AL-100 leveling
plate is recommended for this purpose. To facilitate mounting on a cross arm, an Apogee Instruments model AL-
120 mounting bracket is recommended.
To minimize azimuth error, the sensor should be mounted with the cable pointing toward true north in the
northern hemisphere or true south in the southern hemisphere. Azimuth error is typically less than 0.5 %, but it is
easy to minimize by proper cable orientation.
In addition to orienting the cable to point toward the nearest pole, the sensor should also be mounted such that
obstructions (e.g., weather station tripod/tower or other instrumentation) do not shade the sensor. Once
mounted, the blue cap should be removed from the sensor. The blue cap can be used as a protective covering for
the sensor when it is not in use.
Nylon Screw: 10-32 x 3/8
Model: AL-100
Model: AL-120
Nylon Screw: 10-32 x 3/8

CABLE CONNECTORS
Apogee started offering cable connectors 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.
Cable connectors are attached directly to the head.
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 a replacement cable is required, please contact
Apogee directly to ensure ordering the proper
pigtail configuration.
Alignment: When reconnecting a 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
sensor head.
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.
WARNING: Do not tighten the connector by
twisting the black cable or sensor head, only twist
the metal connector (yellow arrows).
Finger-tighten firmly

OPERATION AND MEASUREMENT
Connect the sensor to a measurement device (meter, datalogger, controller) capable of measuring and displaying
or recording a millivolt signal (an input measurement range of approximately 0-2.5 V (SQ-642) or 0-5 V (SQ-645) is
required to cover the entire range of PFD from the sun). To maximize measurement resolution and signal-to-noise
ratio, the input range of the measurement device should closely match the output range of the extended range
PFD sensor. DO NOT connect the sensor to a power source greater than 24 V DC.
Wiring for SQ-642 and SQ-645
White: Positive (signal from sensor)
Red: Input power (SQ-642 5-24 V DC, SQ-645 5.5-
24 V DC)
Black: Ground (for sensor signal and input power)
Clear: Shield/Ground