Apogee Instruments SQ-626 User manual

APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA
TEL: [phone] | FAX: [phone] | WEB: APOGEEINSTRUMENTS.COM
Copyright © 2021 Apogee Instrument, Inc.
OWNER’S MANUAL
EXTENDED RANGE PFD SENSOR
Model SQ-626
Rev: 30-August-2021

TABLE OF CONTENTS
Owner’s Manual ............................................................................................................................................................................... 1
Certificate of Compliance............................................................................................................................................................. 3
Introduction.................................................................................................................................................................................. 4
Sensor Models.............................................................................................................................................................................. 5
Specifications................................................................................................................................................................................ 6
Deployment and Installation ........................................................................................................................................................ 8
Software Installation .................................................................................................................................................................... 9
Windows Software ..................................................................................................................................................................... 10
Mac Software ............................................................................................................................................................................. 15
Maintenance and Recalibration ................................................................................................................................................. 20
Troubleshooting and Customer Support .................................................................................................................................... 21
Return and Warranty Policy ....................................................................................................................................................... 22

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-626
Type: Extended Range PFD 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, August 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 Extended Range PFD Sensors consist of a cast acrylic diffuser (filter),
photodiode, and signal processing circuitry mounted in an anodized aluminum housing. A cable to connect the
sensor to a measurement device is also included. SQ-600 series Extended Range PFD Sensors are designed for
continuous photon flux density measurements in indoor environments under LEDs.

SENSOR MODELS
This manual covers the USB quantum sensor, model SQ-626 (listed in bold below). Additional models are covered
in their respective manuals.
Model
Signal
SQ-620
Self-powered
SQ-622
0-2.5 V
SQ-624
4-20 mA
SQ-625
0-5 V
SQ-626
USB
SQ-627
SDI-12
SQ-628
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 PFD sensors are calibrated through side-by-side comparison to the mean of four
transfer standard PFD sensors under a reference lamp. The transfer standard PFD sensors are recalibrated with a
quartz halogen lamp traceable to the National Institute of Standards and Technology (NIST).
SQ-626
Resolution
0.1 µmol m-2 s-1
Calibration Factor
Custom for each sensor and stored in the firmware
Calibration Uncertainty
± 5 % (see calibration Traceability below)
Measurement Range
0 to 4000 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 4000 µmol m-2 s-1)
Response Time
Software updates every second
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 Cosine Response below)
Temperature Response
-0.11± 0.04 % per C
Azimuth Error
Less than 0.5 %
Tilt Error
Less than 0.5 %
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
USB Cable
4.5 m (15 ft)
Current Draw (when Logging)
61 mA

Spectral Response
Cosine Response
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.
Directional, or cosine, response is defined as the
measurement error at a specific angle of radiation
incidence. Error for Apogee SQ-600 series Extended Range
PFD 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 Extended
Range PFD 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 PFD 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

SOFTWARE INSTALLATION
The most recent version of ApogeeConnect software can be downloaded at
http://www.apogeeinstruments.com/downloads/.
Installing the software on a PC (Windows compatible, XP and later)
1. Double click on the installer package:
2. On the ‘Welcome’ screen, please click ‘Next’ to continue.
3. Select the radio button next to “I Agree” to the UELA… and click ‘Next’ to continue.
4. On the ‘Ready to Install the Program’ screen, click ‘Install’ to continue.
5. Click ‘Finish’ to complete the installation. There are shortcuts on your desktop and in your start bar.
Installing the software on a Mac (Mac compatible, 10.10 and later)
1. Double click on the installer package
2. On the ‘Introduction’ screen, please click ‘Continue’ to proceed.
3. Select ‘Continue’ on the ‘Read Me’ screen to continue, this screen contains a history of updates made to
the ApogeeConnect software versions.
4. Select ‘Continue’ on the ‘License’ screen to receive a prompt to agree to the terms of the software license
agreement. Click ‘Agree’ to continue once you receive the prompt.
5. On the ‘Installation Type’ screen, click ‘Install’ to install the software. You can change the location the
software installs to by clicking ‘Change Install Location…’. *Note: You may be prompted for an
administrator password at this time. If you are, proceed by entering your respective password and clicking
‘Install Software’.
6. Once you receive the message “The installation was successful.” on the ‘Summary’ screen click ‘Close’.
Your software is now ready to be used.

WINDOWS SOFTWARE
When the SQ-626 sensor is not plugged into the USB
port, the software will display a message in the lower left
corner, “Device Not Connected,” indicating it cannot
establish communication with the sensor.
Plug the sensor into a USB port and allow some time
for the sensor to automatically establish
communication with the software. Once established,
the message in the lower left corner will display
“Device Connected-Model: SN ####” and real-time PFD
readings will update on the screen. Moving the sensor
closer to a light source should increase the readings,
while blocking all light from the sensor should drop the
reading to zero.

Click the ‘Settings’ icon to display the software
options.
Note ‘Light Source’ is not a selectable option. The SQ-
626 is calibrated for use under LED light sources;
therefore, this function is not necessary for the SQ-
626. The function is designed to give increased
accuracy for the SQ-420.
Clicking ‘Calibration’ will display the factory calibrated
multiplier and offset values. These values are saved in
firmware and can be recovered by clicking the
‘Recover Original’ button. Deriving a new calibration
multiplier and offset is accomplished by clicking the
‘Recalibrate’ button. This is applicable if users want to
calibrate the sensor to their own specific light source.
Note that a reference PFD value of the light source is
required to complete a recalibration.
Note the ‘Immersion Setting’ function is necessary for
the SQ-626. Apply an immersion effect correction
factor of 1.25 to the sensor measurements when the
sensor is being used to take measurements
underwater.

After clicking the ‘Recalibate’ button the user will be
prompted to cover the sensor. Place a dark cap over the
sensor and wait for the real-time PFD reading to settle
at zero. Click OK.
Uncover the sensor and wait for the PFD reading to
settle before entering the reference value. Click OK.
The multiplier and offset values will automatically
calculate and update in the appropriate field. Be sure to
click ‘Save’ to retain the new multiplier and offset.
Clicking ‘Data Logging’ will allow the user to log interval
measurements in a csv file while the software is open
and communicating with the sensor.
Click ‘Setup’ and the Setup Logging window appears.
Click the ‘Browse’ button to create or select a csv file.
Select the desired sampling interval. Note that 1 second
is the minimum interval allowed. Click ‘Start’.

The about screen tells you the software and firmware
versions. These can be used to help troubleshoot if
problems arise.
The data logging window will start to update at the
specified sampling interval and display the Timestamp,
Light Source, and Data Value. At the same time, data will
be written to the csv file. Note that if the csv file is open
in another program new data will not be saved to it.
The data logging window can be closed without affecting
logged data by clicking the ‘Data Logging’ button. The
‘Stop’ button must be clicked to end data logging.
‘Manage Field Logging’ is used to setup the SQ-626 for
use in the field. When the SQ-626 is supplied power
from a USB power source (plug or select batteries) it will
log data which you can retrieve. Choose the interval that
data is saved as well as the interval that data is sampled
and the light source used. The shortest sampling interval
is 1 second. The longest sampling or logging interval is
1440 minutes (1 day). Click ‘Load Settings’ to see current
settings and ‘Save Settings’ to save the settings you want
to the sensor. Note: If you don’t click save the sensor
won’t change the settings.

Click ‘Get Logged Data’ to save the data to your computer.
You will be asked where you want to save the data.
Click ‘Erase Data’ to erase all the saved data. This can’t be
undone.
Before clicking ‘Get Logged Data’ it is important to set the
time of the last logged data point. This is used to back
calculate the timestamps for the remaining data points. If
you just unplugged the sensor and plugged it into the
computer the preloaded day and time should be
sufficient.
Set the sampling interval in minutes or seconds. The
sampling interval is how often a measurement is taken
and logging interval is how often the data is saved. The
logged data is the average of the samples. The logging
interval must be evenly divided by the sampling interval.
For example if the logging interval is 5 minutes and the
sampling interval is 2 minutes it causes an error. But a
sampling interval of 1 minute is acceptable.
To use additional SQ-626 devices, open additional SQ-626 software windows. The device serial number will
display in the lower left hand corner of the corresponding software window. Devices may be selected by serial
number in the tool bar.
When the software is open and logging data from sensor
model SQ-626, it will calculate daily light integral (DLI) in
moles and Dark Hours in hours each day at 12:00 AM
using PFD values collected during the previous 36 hours.
The Dark Hours value is calculated using the “Darkness
Threshold” setting. The number of continuously logged
PFD values less than the Darkness Threshold are counted
and multiplied by the logging interval to calculate the
number of Dark Hours. This represents the longest
continuous duration of darkness, not the total duration of
darkness.

MAC SOFTWARE
When the SQ-626 sensor is not plugged into the USB
port, the software will display a message in the lower left
corner, “Device Not Connected,” indicating it cannot
establish communication with the sensor.
Plug the sensor into a USB port and allow some time
for the sensor to automatically establish
communication with the software. Once established,
the message in the lower left corner will display
“Device Connected SN: ####” and real-time PFD
readings will update on the screen. Moving the sensor
closer to a light source should increase the readings,
while blocking all light from the sensor should drop the
reading to zero.

Note the ‘Immersion Setting’ function is necessary for
the SQ-626. Apply an immersion effect correction
factor of 1.25 to the sensor measurements when the
sensor is being used to take measurements
underwater.
Click the ‘Settings’ icon to display the software options.
Note the ‘Light Source’ function is not necessary for
the SQ-626. The SQ-626 is calibrated for use under LED
light sources; therefore, this function is not necessary
for the SQ-626. The function is designed to give
increased accuracy for the SQ-420.

Clicking ‘Calibration’ will display the factory calibrated
multiplier and offset values. These values are saved in
firmware and can be recovered by clicking the
‘Recover Original’ button. Deriving a new calibration
multiplier and offset is accomplished by clicking the
‘Recalibrate’ button. This is applicable if users want to
calibrate the sensor to their own specific light source.
Note that a reference PFD value of the light source is
required to complete a recalibration.
After clicking the ‘Recalibrate’ button the user will be
prompted to cover the sensor. Place a dark cap over
the sensor and wait for the real-time PFD reading to
settle at zero. Click OK.
Uncover the sensor and wait for the PFD reading to
settle before entering the reference value. Click OK.
The multiplier and offset values will automatically
calculate and update in the appropriate field. Be sure
to click ‘Save’ to retain the new multiplier and offset.

Clicking ‘Data Logging’ will allow the user to log
interval measurements in a csv file while the software
is open and communicating with the sensor.
Click ‘Setup’ and the Setup Logging window appears.
Click the ‘Browse button to create or select a csv file.
Select the desired sampling interval. Note that 1
second is the minimum interval allowed. Click ‘Start’.
The data logging window will start to update at the
specified sampling interval and display the Timestamp,
Light Source, and Data Value. At the same time, data
will be written to the csv file. Note that if the csv file is
open in another program new data will not be saved to
it.
The data logging window can be closed without
affecting logged data by clicking the ‘Exit’ button. The
‘Stop’ button must be clicked to end data logging.
The about screen tells you the software and firmware
versions. These can be used to help troubleshoot if
problems arise.

To use additional SQ-626 devices, open additional SQ-626 software windows. The device serial number will
display in the lower left hand corner of the corresponding software window. Devices may be selected by serial
number in the tool bar.
‘Manage Field Logging’ is used to setup the SQ-626 for the use
in the field. When the SQ-626 is supplied power from a USB
power source (plug or select batteries) it will log data which you
can retrieve. Choose the interval the data is saved as well as the
interval that data is sampled and the light source used. The
shortest sampling interval is 1 second. The longest sampling or
logging interval is 1440 minutes (1 day). Click ‘Load Settings’ to
see current settings and ‘Save Setting’ to save the settings you
want to the sensor. Note: If you don’t click save the sensor
won’t change the settings.
Set the sampling interval in minutes or seconds. The sampling
interval is how often a measurement is taken and logging
interval is how often the data is saved. The logged data is the
average of the samples. The logging interval must be evenly
divided by the sampling interval. For example if the logging
interval is 5 minutes and the sampling interval is 2 minutes it
causes an error. But a sampling interval of 1 minute is
acceptable.
Before clicking ‘Get Logged Data’ it is important to set the
time of the last logged data point. This is used to back
calculate the timestamps for the remaining data points. If you
just unplugged the sensor and plugged it into the computer
the preloaded day and time should be sufficient.
Click ‘Get Logged Data’ to save the data to your computer.
You will be asked where you want to save the data.
Click ‘Erase Data’ to erase all the save data. This can’t be
undone.
When the software is open and logging data from sensor
model SQ-626, it will calculate daily light integral (DLI) in
moles and Dark Hours in hours each day at 12:00 AM using
PFD values collected during the previous 36 hours. The
Dark Hours value is calculated using the “Darkness
Threshold” setting. The number of continuously logged
PFD values less than the Darkness Threshold are counted
and multiplied by the logging interval to calculate the
number of Dark Hours. This represents the longest
continuous duration of darkness, not the total duration of
darkness.

MAINTENANCE AND RECALIBRATION
Blocking of the optical path between the target and detector can cause low readings. Occasionally, accumulated
materials on the diffuser of the upward-looking sensor can block the optical path in three common ways:
1. Moisture or debris on the diffuser.
2. Dust during periods of low rainfall.
3. Salt deposit accumulation from evaporation of sea spray or sprinkler irrigation water.
Apogee Instruments upward-looking sensors have a domed diffuser and housing for improved self-cleaning from
rainfall, but active cleaning may be necessary. Dust or organic deposits are best removed using water, or window
cleaner, and a soft cloth or cotton swab. Salt deposits should be dissolved with vinegar and removed with a cloth
or cotton swab. Salt deposits cannot be removed with solvents such as alcohol or acetone. Use only gentle
pressure when cleaning the diffuser with a cotton swab or soft cloth to avoid scratching the outer surface. The
solvent should be allowed to do the cleaning, not mechanical force. Never use abrasive material or cleaner on the
diffuser.
It is recommended that two-band radiometers be recalibrated every two years. See the Apogee webpage for
details regarding return of sensors for recalibration (http://www.apogeeinstruments.com/tech-support-
recalibration-repairs/).