Apogee Instruments SQ-500 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-500

(including SS model, formerly gold)

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............................................................................................................................................. 17 
Troubleshooting and Customer Support................................................................................................................................ 19 
Return and Warranty Policy................................................................................................................................................... 20 
 

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-500

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, April 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 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-500 series quantum sensors consist of a cast acrylic diffuser (filter), interference 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-500 model quantum sensor outputs a voltage that is directly

proportional to PPFD. 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 unamplified analog output quantum sensor, model SQ-500 (listed in bold below).

Additional models are covered in their respective manuals.

Model

Signal

SQ-500

0-40 mV

SQ-512

0-2.5 V

SQ-515

0-5 V

SQ-520

USB

SQ-521

SDI-12

SQ-522

Modbus

Sensor model number and serial number are

located near the pigtail leads on the sensor cable.

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-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-500-SS

Power Supply

Self-powered

Sensitivity

0.01 mV per µmol m-2 s-1

Calibration Factor

100 µmol m-2 s-1 per mV

Calibration Uncertainty

± 5 % (see Calibration Traceability below)

Measurement Range

0 to 4000 µmol m-2 s-1

Measurement

Repeatability

Less than 0.5 %

Calibrated Output Range

0 to 40 mV

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

Less than 1 ms

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

24 mm diameter, 37 mm height

Mass (with 5 m of cable)

100 g

Cable

5 m of two conductor, shielded, twisted-pair wire; TPR jacket; pigtail lead wires; stainless steel

(316), M8 connector located 25 cm from sensor head

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 AM-110

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 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-110

Model: AL-120

Nylon Screw: 10-32 x 3/8

CABLE CONNECTORS

Apogee started offering in-line cable connectors on

some bare-lead wire sensors in March 2018 to simplify

the process of removing sensors from installations for

recalibration (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

sensor 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 an installation, 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 back for recalibration, only send the

section of cable that is hard-wired to the sensor. The

section of cable with the pigtail is not required.

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, one to two

threads may still be visible.

WARNING: Do not tighten the connector by twisting

the black cable, only twist the metal connector.

Finger-tighten firmly.

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