Apogee Instruments SQ-522 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 SENSOR
Model SQ-522
Rev: 2-Aug-2021

TABLE OF CONTENTS
Owner’s Manual ............................................................................................................................................................1
Certificate of Compliance ......................................................................................................................................3
Introduction...........................................................................................................................................................4
Sensor Models .......................................................................................................................................................5
Specifications.........................................................................................................................................................6
Deployment and Installation .................................................................................................................................9
Cable Connectors.................................................................................................................................................10
Operation and Measurement..............................................................................................................................10
Maintenance and Recalibration ..........................................................................................................................20
Troubleshooting and Customer Support .............................................................................................................22
Return and Warranty Policy ................................................................................................................................23

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-522
Type: Quantum 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 rely on the information provided to us by our material suppliers.
Signed for and on behalf of:
Apogee Instruments, January 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), the sum of photons from 400 to 700 nm in units of micromoles per square meter per second (µmol
m-2 s-1, equal to microEinsteins m-2 s-1). While microEinsteins and micromoles are equal (one Einstein = one mole of
photons), the Einstein is not an SI unit, so expressing PPFD as µmol m-2 s-1 is preferred. Daily total PPFD is typically
reported in units of moles of photons per square meter per day (mol m-2 d-1) and is often called daily light integral
(DLI).
The acronym PPF is also used and refers to the photosynthetic photon flux. The acronyms PPF and PPFD refer to
the same variable. Both terms are used because there is not a universal definition of the term flux. Flux is
sometimes defined as per unit area per unit time and sometimes defined as per unit time only. PPFD is used in this
manual.
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.
Typical applications of quantum sensors include measurement of incident PPFD on plant canopies in outdoor
environments or in greenhouses and growth chambers, and reflected or under-canopy (transmitted) PPFD
measurement in the same environments.
Apogee Instruments SQ series quantum 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-500 series quantum sensors are designed for continuous PPFD measurement in indoor or
outdoor environments. The SQ-522 sensors output a digital signal using Modbus RTU protocol over RS-232 or RS-
485.

SENSOR MODELS
This manual covers the Modbus RTU communication protocol, full-spectrum quantum sensor model SQ-522 (in
bold below). Additional models are covered in their respective manuals.
Model
Signal
SQ-522
Modbus
SQ-500
Self-powered
SQ-512
Amplified 0 to 2.5 V signal output
SQ-515
Amplified 0 to 5 V signal output
SQ-520
USB
SQ-521
SDI-12
Sensor model number and serial number are
located on the bottom of the sensor. If you need
the manufacturing date of your sensor, please
contact Apogee Instruments with the serial
number of your sensor.

SPECIFICATIONS
Calibration Traceability
Apogee Instruments SQ-500 series quantum sensors are calibrated through side-by-side comparison to the mean
of four transfer standard quantum sensors under a reference lamp. The reference quantum sensors are
recalibrated with a quartz halogen lamp traceable to the National Institute of Standards and Technology (NIST).
SQ-522
Input Voltage
5.5 to 24 V DC
Average Max Current Draw
RS-232 37 mA;
RS-485 quiescent 37 mA, active 42 mA
Calibration Factor
Custom for each sensor and stored in the firmware
Calibration Uncertainty
± 5 % (see calibration Traceability below)
Measurement Repeatability
Less than 1 % (up to 4000 µmol m-2 s-1)
Long-term Drift
(Non-stability)
Less than 2 % per year
Non-linearity
Less than 1 % (up to 4000 µmol m-2 s-1)
Field of View
180°
Spectral Range
389 to 692 nm ± 5 nm (wavelengths where response is greater than 50 %)
Spectral Selectivity
Less than 10 % from 412 to 682 ± 5 nm (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 (see Temperature Response below)
Uncertainty in Daily Total
Less than 5 %
Detector
Blue-enhanced silicon photodiode
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 shielded, twisted-pair wire; TPR jacket (high water resistance, high UV stability,
flexibility in cold conditions); pigtail lead wires; stainless steel (316), M8 connector

Spectral Response
Temperature Response
Mean temperature response of ten SQ-500
series quantum sensors (errors bars
represent two standard deviations above
and below mean). Temperature response
measurements were made at 10 C intervals
across a temperature range of approximately
-10 to 40 C in a temperature controlled
chamber under a fixed, broad spectrum,
electric lamp. At each temperature set point,
a spectroradiometer was used to measure
light intensity from the lamp and all quantum
sensors were compared to the
spectroradiometer. The spectroradiometer
was mounted external to the temperature
control chamber and remained at room
temperature during the experiment.
Mean spectral response measurements of
six replicate Apogee SQ-100 (original) and
SQ-500 (full-spectrum) series quantum
sensors. Spectral response measurements
were made at 10 nm increments across a
wavelength range of 300 to 800 nm with a
monochromator and an attached electric
light source. Measured spectral data from
each quantum sensor were normalized by
the measured spectral response of the
monochromator/electric light combination,
which was measured with a
spectroradiometer.

Cosine Response
Mean directional (cosine) response of
seven apogee SQ-500 series quantum
sensors. Directional response
measurements were made on the
rooftop of the Apogee building in Logan,
Utah. Directional response was
calculated as the relative difference of
SQ-500 quantum sensors from the mean
of replicate reference quantum sensors
(LI-COR models LI-190 and LI-190R, Kipp
& Zonen model PQS 1). Data were also
collected in the laboratory using a
reference lamp and positioning the
sensor at varying angles.
Directional (cosine) response is defined as the measurement
error at a specific angle of radiation incidence. Error for
Apogee SQ-500 series quantum sensors is approximately ± 2
% and ± 5 % at solar zenith angles of 45° and 75°,
respectively.

Important: Only use the nylon screw provided
when mounting to insulate the non-anodized
threads of the aluminum sensor head from the
base to help prevent galvanic corrosion. For
extended submersion applications, more insulation
may be necessary. Contact Apogee tech support for
details.
DEPLOYMENT AND INSTALLATION
Mount the sensor to a solid surface with the nylon mounting screw provided. To accurately measure PPFD 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 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.
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