Apogee Instruments SP-420 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
USB PYRANOMETER
Models SP-420

TABLE OF CONTENTS
Owner’s Manual ............................................................................................................................................................................... 1
Certificate of Compliance......................................................................................................................................................... 3
Introduction ............................................................................................................................................................................. 4
Sensor Models ......................................................................................................................................................................... 5
Specifications ........................................................................................................................................................................... 6
Deployment and Installation.................................................................................................................................................... 9
Software Installation.............................................................................................................................................................. 10
Operation and Measurement ................................................................................................................................................ 11
Windows Software................................................................................................................................................................. 13
MAC software ........................................................................................................................................................................ 18
Maintenance and Recalibration............................................................................................................................................. 24
Troubleshooting and Customer Support................................................................................................................................ 26
Return and Warranty Policy................................................................................................................................................... 27

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: SP-420
Type: Pyranometer
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
Solar radiation at Earth’s surface is typically defined as total radiation across a wavelength range of 280 to 4000
nm (shortwave radiation). Total solar radiation, direct beam and diffuse, incident on a horizontal surface is defined
as global shortwave radiation, or shortwave irradiance (incident radiant flux), and is expressed in Watts per square
meter (W m-2, equal to Joules per second per square meter).
Pyranometers are sensors that measure global shortwave radiation. Apogee SP series pyranometers are silicon-cell
pyranometers, and are only sensitive to a portion of the solar spectrum, approximately 350-1100 nm
(approximately 80 % of total shortwave radiation is within this range). However, silicon-cell pyranometers are
calibrated to estimate total shortwave radiation across the entire solar spectrum. Silicon-cell pyranometer
specifications compare favorably to specifications for World Meteorological Organization (WMO) moderate and
good quality classifications and specifications for International Organization of Standardization (ISO) Class C
classification, but because of limited spectral sensitivity, they do not meet the spectral specification necessary for
WMO certification.
Typical applications of silicon-cell pyranometers include incoming shortwave radiation measurement in
agricultural, ecological, and hydrological weather networks, and solar panel arrays.
Apogee Instruments SP series pyranometers 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 total
shortwave radiation measurement on a planar surface in outdoor environments. The SP-420 outputs a signal that
is directly proportional to total shortwave radiation from the sun. The voltage signal from 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 USB smart sensor model SP-420. Additional models are covered in their respective
manuals.
Model
Signal
SP-420
USB
SP-110
Self-powered
SP-230*
Self-powered
SP-212
0-2.5 V
SP-214
4-20 mA
SP-215
0-5 V
SP-421
SDI-12
SP-422
Modbus
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.

SPECIFICATIONS
Calibration Traceability
Apogee Instruments SP series pyranometers are calibrated through side-by-side comparison to the mean of four
Apogee model SP-110 transfer standard pyranometers (shortwave radiation reference) under high intensity
discharge metal halide lamps. The transfer standard pyranometers are calibrated through side-by-side comparison
to the mean of at least two ISO-classified reference pyranometers under sunlight (clear sky conditions) in Logan,
Utah. Each of four ISO-classified reference pyranometers are recalibrated on an alternating year schedule (two
instruments each year) at the National Renewable Energy Laboratory (NREL) in Golden, Colorado. NREL reference
standards are calibrated to the World Radiometric Reference (WRR) in Davos, Switzerland.
SP-420
ISO 9060:2018
Class C (previously known as second class)
Resolution
0.1 W m-2
Calibration Factor
Custom for each sensor and stored in firmware
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 1750 W m-2)
Response Time
Software updates every second
Field of View
180°
Spectral Range
360 to 1120 nm (wavelengths where response is 10 % of maximum;
see Spectral Response below)
Directional (Cosine) Response
± 5 % at 75° zenith angle (see Cosine Response below)
Temperature Response
0.04 ± 0.04 % 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
24 mm diameter, 33 mm height
Mass
Sensor head weighs 90 g
USB Cable
4.5 m (15 ft)
Current Draw (when Logging)
61 mA

Spectral Response
Temperature Response
Mean temperature response of four
Apogee silicon-cell pyranometers.
Temperature response measurements
were made at approximately 10 C
intervals across a temperature range of
approximately -10 to 50 C under
sunlight. Each pyranometer had an
internal thermistor to measure
temperature. At each temperature set
point, a reference blackbody
pyranometer was used to measure solar
intensity.
Spectral response estimate of Apogee
silicon-cell pyranometers. Spectral
response was estimated by multiplying
the spectral response of the
photodiode, diffuser, and adhesive.
Spectral response measurements of
diffuser and adhesive were made with a
spectrometer, and spectral response
data for the photodiode were obtained
from the manufacturer.

Cosine Response
Mean cosine response of eleven Apogee
silicon-cell pyranometers (error bars
represent two standard deviations
above and below mean). Cosine
response measurements were made
during broadband outdoor radiometer
calibrations (BORCAL) performed during
two different years at the National
Renewable Energy Laboratory (NREL) in
Golden, Colorado. Cosine response was
calculated as the relative difference of
pyranometer sensitivity at each solar
zenith angle to sensitivity at 45° solar
zenith angle. The blue symbols are AM
measurements, the red symbols are PM
measurements.
Directional, or cosine, response is
defined as the measurement error at
a specific angle of radiation incidence.
Error for Apogee silicon-cell
pyranometers 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.

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.

OPERATION AND MEASUREMENT
Spectral Errors for Measurements with Silicon-cell Pyranometers
Apogee SP series pyranometers are calibrated under electric lamps in a calibration laboratory. The calibration
procedure simulates calibration under clear sky conditions at a solar zenith angle of approximately 45°. However,
due to the limited spectral sensitivity of silicon-cell pyranometers compared to the solar radiation spectrum (see
graph below), spectral errors occur when measurements are made in conditions that differ from conditions the
sensor was calibrated under (e.g., the solar spectrum differs in clear sky and cloudy conditions, thus measurements
in cloudy conditions result in spectral error because sensors are calibrated in clear sky conditions).
Silicon-cell pyranometers can still be used to measure shortwave radiation in conditions other than clear sky or
from radiation sources other than incoming sunlight, but spectral errors occur when measuring radiation with
silicon-cell pyranometers in these conditions. The graphs below show spectral error estimates for Apogee silicon-
cell pyranometers at varying solar zenith angles and varying atmospheric air mass. The diffuser is optimized to
minimize directional errors, thus the cosine response graph in the Specifications section shows the actual
directional errors in practice (which includes contributions from the spectral shift that occurs as solar zenith angle
and atmospheric air mass change with time of day and time of year). The table below provides spectral error
estimates for shortwave radiation measurements from shortwave radiation sources other than clear sky solar
radiation.
Spectral response of Apogee SP series
pyranometers compared to solar
radiation spectrum at Earth’s surface.
Silicon-cell pyranometers, such as
Apogee SP series, are only sensitive to
the wavelength range of
approximately 350-1100 nm, and are
not equally sensitive to all
wavelengths within this range. As a
result, when the spectral content of
solar radiation is significantly different
than the spectrum that silicon-cell
pyranometers were calibrated to,
spectral errors result.

Spectral error for Apogee SP series
pyranometers as a function of
atmospheric air mass, assuming
calibration at an air mass of 1.5.
Spectral error for Apogee SP series
pyranometers as a function of solar
zenith angle, assuming calibration at
a zenith angle of 45°.

WINDOWS SOFTWARE
When the SP-420 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 shortwave
radiation 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.

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 value of the light source is
required to complete a recalibration.
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 shortwave readiation
reading to settle at zero. Click OK.
Click the ‘Settings’ icon to display the software
options. Note ‘Light Source’ is not a setting for the SP-
420.

Uncover the sensor and wait for the shortwave
radiation 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
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.
‘Manage Field Logging’ is used to setup the SP-420 for
use in the field. When the SP-420 is supplied power from
a USB power source 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.

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 saved data. This can’t be
undone.
To use additional SP-420 devices, open additional ApogeeConnect 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.

MAC SOFTWARE
When the SP-420 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
shortwave radiation 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 setting option for the SP-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 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 shortwave
radiation reading to settle at zero. Click OK.
Uncover the sensor and wait for the shortwave
radiation 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’.