Apogee Instruments SQ-422 User manual

APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA
TEL: [phone] | FAX: [phone] | WEB: APOGEEINSTRUMENTS.COM
Copyright © 2020 Apogee Instruments, Inc.
OWNER’S MANUAL
QUANTUM SENSOR
Model SQ-422

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 ................................................................................................................................................ 11
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-422
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, June 2020
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 often expressed as photosynthetic photon flux density
(PPFD): photon flux 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). While
Einsteins 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.
The acronym PPF is also widely used and refers to the photosynthetic photon flux. The acronyms PPF and PPFD
refer to the same parameter. The two terms have co-evolved because there is not a universal definition of the
term “flux”. Some physicists define flux as per unit area per unit time. Others define flux only as per unit time.
We have used PPFD in this manual because we feel that it is better to be more complete and possibly redundant.
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 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.
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. Sensors are potted solid with no internal air space, and are designed for continuous PPFD
measurement in indoor or outdoor environments. The SQ-422 model outputs a digital signal using Modbus RTU
communication protocol over RS-232 or RS-485.

SENSOR MODELS
This manual covers the Modbus RTU communication protocol, original quantum sensor model SQ-422 (in bold
below). Additional models are covered in their respective manuals.
Model
Signal
Calibration
SQ-422
Modbus
Sunlight and Electric
light
SQ-110
Self-powered
Sunlight
SQ-120
Self-powered
Electric light
SQ-311
Self-powered
Sunlight
SQ-313
Self-powered
Sunlight
SQ-316
Self-powered
Sunlight
SQ-212
0-2.5 V
Sunlight
SQ-222
0-2.5 V
Electric light
SQ-214
4-20 mA
Sunlight
SQ-224
4-20 mA
Electric light
SQ-215
0-5 V
Sunlight
SQ-225
0-5 V
Electric light
SQ-420
USB
Sunlight and Electric
light
SQ-421
SDI-12
Sunlight and Electric
light
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 SQ series quantum sensors are calibrated through side-by-side comparison to the mean of transfer
standard quantum sensors under a reference lamp. The reference quantum sensors are recalibrated with a 200 W
quartz halogen lamp traceable to the National Institute of Standards and Technology (NIST).
SQ-422
Input Voltage Requirement
5.5 to 24 V DC
Average Max Current Draw
RS-232 quiescent 36.87 mA, active 37.06 mA;
RS-485 quiescent 37.37 mA, active 42.30 mA
Calibration Uncertainty
± 5 % (see Calibration Traceability below)
Measurement Repeatability
Less than 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
410 to 655 nm (wavelengths where response is greater than 50% of maximum; see Spectral
Response below)
Directional (Cosine) Response
± 5 % at 75° zenith angle (see Cosine Response below)
Temperature Response
0.06 ± 0.06 % per C (see Temperature Response below)
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 diameter
Mass (with 5 m of cable)
140 g
Cable
5 m of two conductor, 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 eight SQ-100
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 of six SQ-100 series
quantum sensors (error bars represent two
standard deviations above and below
mean) compared to defined plant response
to photons. 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.
Slope = 0.06 %

Cosine Response
Mean directional (cosine) response of
six apogee SQ-100 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-100
series quantum sensors is approximately ± 2
% and ± 5 % at solar zenith angles of 45° and
75°, respectively.

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 to level the sensor when used on a flat surface or being mounted to surfaces such as wood. To
facilitate mounting on a mast or pipe, the Apogee Instruments model AL-120 Solar Mounting Bracket with Leveling
Plate 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 1 %, 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: 10-32x3/8
Nylon Screw: 10-32x3/8
Model AL-100
Model AL-120
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.

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 connection to a measurement
device, the unused pigtail lead wire colors are
removed.
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 (blue arrows).
Finger-tighten firmly