Apogee Instruments SQ-421 User manual

APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA

TEL: (435) 792-4700 | FAX: (435) 787-8268 | WEB: APOGEEINSTRUMENTS.COM

OWNER’S MANUAL

QUANTUM SENSOR

Model SQ-421

Rev: 28-Oct-2020

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............................................................................................................................................. 21

Troubleshooting and Customer Support................................................................................................................................ 23

Return and Warranty Policy................................................................................................................................................... 24

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-421

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, October 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. SQ-421 model sensors output a digital signal using SDI-12

communication protocol.

SENSOR MODELS

This manual covers the SDI-12 communication protocol, original quantum sensor model SQ-421. Additional models

are covered in their respective manuals.

Model

Signal

Calibration

SQ-421

SDI-12

Sunlight and Electric light

SQ-110

Self-powered

Sunlight

SQ-120

Self-powered

Electric light

SQ-311

Self-powered

Sunlight

SQ-321

Self-powered

Electric light

SQ-313

Self-powered

Sunlight

SQ-323

Self-powered

Electric light

SQ-316

Self-powered

Sunlight

SQ-326

Self-powered

Electric light

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-422

ModBus

Sunlight and Electric light

Serial Number 0-2400: Sensor model

number and serial number are located

near the pigtail leads on the sensor cable.

If you need the manufacturing date of

your sensor, please contact Apogee

Instruments with the serial number of your

sensor.

Serial Numbers 2401 and above: 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--421

Input Voltage

Requirement

5.5 to 24 V DC

Current Drain

1.4 mA (quiescent), 1.8 mA (active)

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)

Response Time

0.6 s, time for detector signal to reach 95 % following a step change; fastest data transmission rate

for SDI-12 circuitry is 1 s

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

Serial # 2401 and above

30.5 mm diameter, 37 mm height

Dimensions

Serial # 0-2400

44.0 mm height, 23.5 mm diameter

Mass (with 5 m cable)

Serial # 2401 and above

140 g

Mass (with 5 m cable)

Serial # 0-2400

117 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.

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 green cap should be removed from the sensor. The green 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

Nylon Screw: 10-32 x 3/8

Model AL-120

CABLE CONNECTORS

Apogee sensors offer 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 (blue arrows).

Finger-tighten firmly

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