Apogee Instruments SU-202 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
ULTRAVIOLET-A SENSOR
Models SU-202 and SU-205
(including SS models)

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............................................................................................................................................. 14
Troubleshooting and Customer Support................................................................................................................................ 15
Return and Warranty Policy................................................................................................................................................... 17

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: SU-202, SU-205
Type: Ultraviolet-A 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, January 2020
Bruce Bugbee
President
Apogee Instruments, Inc.

INTRODUCTION
Ultraviolet (UV) radiation constitutes a portion of the electromagnetic spectrum from 100 to 400 nm and is further
subdivided into three wavelength ranges: UV-A (315 to 400 nm), UV-B (280 to 315 nm), and UV-C (100 to 280 nm).
Much of the UV-B and all of the UV-C wavelengths from the sun are absorbed by Earth’s atmosphere. There are
also multiple artificial UV light sources available.
Most UV sensors designed for sunlight measurements are sensitive to UV radiation in the UV-A or UV-B ranges.
Apogee Instruments SU-200 series UV-A sensors detect UV radiation from 300 to 400 nm and are calibrated in
energy flux density units of watts per square meter (W m-2, equal to Joules per second per square meter). The
output can also be expressed in photon flux density units of micromoles per square meter per second (µmol m-2 s-
1).
Typical applications of UV sensors include incoming UV radiation measurement in outdoor environments or in
laboratory use with artificial light sources (e.g., germicidal lamps).
Apogee Instruments SU-200 series UV-A sensors consist of a cast acrylic diffuser, photodiode, and signal processing
circuitry mounted in an anodized aluminum housing and a cable to connect the sensor to a measurement device.
SU-200 sensors are designed for continuous UV-A radiation measurement in indoor or outdoor environments. The
SU-200 series outputs an analog voltage that is directly proportional to UV-A radiation incident on a planar surface
(does not have to be horizontal) where the radiation emanates from all angles of a hemisphere.

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.
SENSOR MODELS
This manual covers the amplified model SU-202 and SU-205 UV-A sensors (listed below in bold). Additional models
are covered in their respective manuals.
Model
Signal
SU-200
0-10 mV
SU-202
0- 2.5 V
SU-205
0- 5 V

SPECIFICATIONS
Calibration Traceability
Apogee UV series sensors are calibrated through side-by-side comparison to the mean of four transfer standard UV
sensors under UV-enhanced T5 fluorescent tubes. The transfer standard UV sensors are calibrated through side-
by-side comparison to an Apogee model PS-300 spectroradiometer under sunlight (clear sky conditions) in Logan,
Utah. The PS-300 is calibrated with a quartz halogen lamp traceable to the National Institute of Standards and
Technology (NIST).
SU-202-SS
SU-205-SS
Power Supply
3.3 to 24 V DC
5.5 to 24 V DC
Output (sensitivity)
25 mV per W m-2;
8.33 mV per µmol m⁻² s⁻¹
50 mV per W m-2;
16.67 mV per µmol m⁻² s⁻¹
Calibration Factor (reciprocal of
sensitivity)
0.04 W m-2 per mV;
0.12 µmol m⁻² s⁻¹ per mV
0.02 W m-2 per mV;
0.06 µmol m⁻² s⁻¹ per mV
Calibration Uncertainty
± 10 %
Output Range
0 to 2.5 V
0 to 5 V
Measurement Range
0 to 100 W m-2
Measurement Repeatability
Less than 0.5 %
Long-term Drift
Less than 2 % per year
Non-linearity
Less than 1 %
Response Time
Less than 1 ms
Field of View
180°
Spectral Range
300 to 400 nm (wavelengths where response is greater than 10 % of maximum; see
Spectral Response below)
Directional (Cosine) Response
± 2 % at 45°, ± 5 % at 70°
Temperature Response
Less than 0.1 % per C
Operating Environment
-30 to 85 C; 0 to 100 % relative humidity
Dimension
30.5 mm diameter, 37 mm height
Mass (5 m of cable)
140 g
Cable
5 m of shielded, twisted-pair wire; TPR jacket (high water resistance, high UV stability,
flexibility in cold conditions); pigtail lead wires; stainless steel (316), M8 connector

Cosine Response
Cosine Response Graph
Directional, or cosine, response is
defined as the measurement error at
a specific angle of radiation incidence.
Directional error for Apogee SU-200
series UV-A sensors is approximately ±
2 % and ± 5 % at solar zenith angles of
45° and 75°, respectively.
Mean cosine response of four
Apogee UV-A sensors. Cosine
response was calculated as the
relative difference of UV-A
sensors from the mean of
replicate reference UV-A
sensors deployed outdoors.
These data are the average of
the AM and PM response.

Spectral Response
Spectral response
estimate of Apogee SU-
200 UV-A sensors.
Spectral response was
modeled from sensitivity
of the photodetector and
transmittance of the
diffuser.

DEPLOYMENT AND INSTALLATION
Mount the sensor to a solid surface with the nylon mounting screw provided. To accurately measure UV-A 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 black cap should be removed from the sensor. The black cap can be used as a protective covering
for the sensor when it is not in use.
Nylon Screw: 10-32x3/8
Model AL-100
Nylon Screw: 10-32x3/8
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

OPERATION AND MEASUREMENT
Connect the sensor to a measurement device (meter, datalogger, controller) capable of measuring and displaying
or recording a millivolt signal (an input measurement range of approximately 0-2.5 V (SU-202) or 0-5 V (SU-205) is
required to cover the entire range of UV-A from the sun). In order to maximize measurement resolution and signal-
to-noise ratio, the input range of the measurement device should closely match the output range of the UV sensor.
The amplification circuit requires a power supply of 3.3 to 24 V DC (SU-202) or 5.5 to 24 V DC (SU-205). NOTE: to
prevent sensor damage, DO NOT connect the sensor to a power source greater than 24 V DC.
Wiring for SU-202 and SU-205
Black: Negative (signal from sensor)
Red: Power in (3.3-24 V DC or 5.5-24 V DC)
White: Output Signal
Clear: Shield

Sensor Calibration
All Apogee amplified UV sensor models SU-202 and SU-205 have a standard UV calibration factor of exactly:
SU-202: 0.04 W m-2 per mV
SU-205: 0.02 W m-2 per mV
The following example uses the SU-202 calibration factor and expected response under full sunlight:
Calibration Factor (0.04 W m-2 per mV) * Sensor Output Signal (mV) = UV-A (W m-2)
0.04 * 1500 = 60
Example of UV-A measurement with an Apogee SU-202
sensor. Full sunlight yields UV-A radiation on a horizontal
plane at the Earth’s surface of approximately 60 W m-2. This
yields an output signal of 1500 mV. The signal is converted to
UV-A radiation by multiplying by the calibration factor of 0.04
W m-2 per mV.
Sensor Output
1500 mV
Full Sunlight
60 W m-2
UV-A

UV-A Measurements and Spectral Errors
Apogee Instruments model SU-200 UV-A sensors are calibrated to measure ultraviolet radiation from the sun
between 300 and 400 nm in Watts per square meter. In addition to naturally occurring UV-A radiation from the
sun, there are many electric light sources that emit UV-A radiation (e.g., cool white fluorescent, metal halide,
mercury arc, and germicidal lamps). Although the relative wavelengths of UV-A radiation differ among sunlight and
electric lights, the error estimates shown in the table below indicate the SU-200 provides reasonable estimates of
UV-A radiation coming from electric lamps (table provides spectral error estimates for UV-A radiation
measurements from radiation sources other than clear sky solar radiation). For most common lamps, the error is
less than 10 %. The SU-200 is particularly useful for determining the UV-A filtering capacity of the transparent
plastic and glass barriers that are commonly used below electric lamps.
Radiation Source (Error Calculated Relative to Sun, Clear Sky)
SU-200 Series Irradiance Error [%]
Clear Sky
0.0
Overcast
-0.6
Direct Normal
-0.4
Diffused Blue Light
0.5
UV-Enhanced T5 Cool White Fluorescent
-6.4
T5 Cool White Fluorescent
15.0
Metal Halide
-0.6
Mercury Arc
20.5
T12 Fluorescent UV-A Enhanced
12.0

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 SU-200 series UV-A sensors can block the optical path in three common ways:
1. Moisture or debris build-up on the diffuser.
2. Dust during periods of low rainfall.
3. Salt deposit accumulation from evaporation of sea spray or sprinkler irrigation water.
SU-200 series 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.
Never use solvents such as alcohol or acetone to clean the sensor. Use only gentle pressure when cleaning the
diffuser with a cotton swab or soft cloth, to avoid scratching the outer surface. The vinegar should be allowed to
do the cleaning, not mechanical force. Never use an abrasive material or cleaner on the diffuser.
It is recommended that UV-A sensors 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/).

TROUBLESHOOTING AND CUSTOMER SUPPORT
Independent Verification of Functionality
Apogee SU-202 and SU-205 sensors provide an amplified voltage output that is proportional to incident UV-A
radiation. A quick and easy check of sensor functionality can be determined using a DC power supply and a
voltmeter. Power the sensor with a DC voltage by connecting the positive voltage signal to the red wire from the
sensor and the negative (or common) to the black wire from the sensor. Use the voltmeter to measure across the
white wire (output signal) and black wire. Direct the sensor head toward a light source and verify the sensor
provides a signal. Increase and decrease the distance from the sensor head to the light source to verify that the
signal changes proportionally (decreasing signal with increasing distance and increasing signal with decreasing
distance). Blocking all radiation from the sensor should force the sensor signal to zero.
Compatible Measurement Devices (Dataloggers/Controllers/Meters)
SU-202 UV-A sensors are calibrated with a standard calibration factor of 0.04 W m-2 per mV, yielding a sensitivity of
25 mV per W m-2, and the SU-205 UV-A sensors are calibrated with a standard calibration factor of 0.02 W m-2 per
mV yielding a sensitivity of 50 mV per W m-2. Thus, a compatible measurement device (e.g., datalogger or
controller) should have resolution of at least 25 mV or 50 mV to provide a measurement resolution of 1 W m-2
respectively.
An example datalogger program for Campbell Scientific dataloggers can be found on the Apogee webpage at
http://www.apogeeinstruments.com/content/UV-Sensor.CR1.
Zero Offset Error
With the use of certain dataloggers it is possible to measure a non-zero voltage (zero offset) when the sensor
output should be zero (no UV irradiance incident on diffuser). This offset can be corrected by adding or subtracting
the measured offset from the sensor output. However, if the offset is substantial, and your sensor is outputting
unrealistic values then it may need to be recalibrated. In this case, contact Apogee customer support to recalibrate
the sensor.
Cable Length
When the sensor is connected to a measurement device with high input impedance, sensor output signals are not
changed by shortening the cable or splicing on additional cable in the field. Tests have shown that if the input
impedance of the measurements device is greater than 1 mega-ohm there is negligible effect on the calibration,
even after adding up to 100 m of cable. All Apogee sensors use shielded, twisted pair cable to minimize
electromagnetic interference. For best measurements, the shield wire must be connected to an earth ground. This
is particularly important when using the sensor with long lead lengths in electromagnetically noisy environments.
Modifying Cable Length
See Apogee webpage for details on how to extend sensor cable length at
http://www.apogeeinstruments.com/how-to-make-a-weatherproof-cable-splice/.

Unit Conversion
SU-200 series UV-A sensors are calibrated in energy flux units of W m-2. It is possible to convert the energy flux
value to photon flux units of µmol m-2 s-1 using a conversion factor. Below is an example of how to convert energy
flux units to photon flux.
1) Calculate the sensor output in units of J m-2 s-1.
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2) Multiply the energy flux units by the conversion factor. It’s important to note that each light source needs
a specific conversion factor. The conversion factor used in the example equation is the sunlight
conversion factor.s
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RETURN AND WARRANTY POLICY
RETURN POLICY
Apogee Instruments will accept returns within 30 days of purchase as long as the product is in new condition (to be
determined by Apogee). Returns are subject to a 10 % restocking fee.
WARRANTY POLICY
What is Covered
All products manufactured by Apogee Instruments are warranted to be free from defects in materials and craftsmanship
for a period of four (4) years from the date of shipment from our factory. To be considered for warranty coverage an
item must be evaluated either at our factory or by an authorized distributor.
Products not manufactured by Apogee (spectroradiometers, chlorophyll content meters, EE08-SS probes) are covered
for a period of one (1) year.
What is Not Covered
The customer is responsible for all costs associated with the removal, reinstallation, and shipping of suspected warranty
items to our factory.
The warranty does not cover equipment that has been damaged due to the following conditions:
1. Improper installation or abuse.
2. Operation of the instrument outside of its specified operating range.
3. Natural occurrences such as lightning, fire, etc.
4. Unauthorized modification.
5. Improper or unauthorized repair.
Please note that nominal accuracy drift is normal over time. Routine recalibration of sensors/meters is considered part of
proper maintenance and is not covered under warranty.
Who is Covered
This warranty covers the original purchaser of the product or other party who may own it during the warranty period.
What Apogee Will Do
At no charge Apogee will:
1. Either repair or replace (at our discretion) the item under warranty.
2. Ship the item back to the customer by the carrier of our choice.
Different or expedited shipping methods will be at the customer’s expense.
How To Return An Item
1. Please do not send any products back to Apogee Instruments until you have received a Return Merchandise

Authorization (RMA) number from our technical support department by calling [phone] or by submitting an
online RMA form at www.apogeeinstruments.com/tech-support-recalibration-repairs/. We will use your RMA number
for tracking of the service item.
2. Send all RMA sensors and meters back in the following condition: Clean the sensor’s exterior and cord. Do not modify
the sensors or wires, including splicing, cutting wire leads, etc. If a connector has been attached to the cable end, please
include the mating connector –otherwise the sensor connector will be removed in order to complete the
repair/recalibration.
3. Please write the RMA number on the outside of the shipping container.
4. Return the item with freight pre-paid and fully insured to our factory address shown below. We are not responsible for
any costs associated with the transportation of products across international borders.
5. Upon receipt, Apogee Instruments will determine the cause of failure. If the product is found to be defective in terms
of operation to the published specifications due to a failure of product materials or craftsmanship, Apogee Instruments
will repair or replace the items free of charge. If it is determined that your product is not covered under warranty, you
will be informed and given an estimated repair/replacement cost.
Apogee Instruments, Inc.
721 West 1800 North Logan, UT
84321, USA
PRODUCTS BEYOND THE WARRANTY PERIOD
For issues with sensors beyond the warranty period, please contact Apogee at techsup[email protected] to
discuss repair or replacement options.
OTHER TERMS
The available remedy of defects under this warranty is for the repair or replacement of the original product, and Apogee
Instruments is not responsible for any direct, indirect, incidental, or consequential damages, including but not limited to
loss of income, loss of revenue, loss of profit, loss of wages, loss of time, loss of sales, accruement of debts or expenses,
injury to personal property, or injury to any person or any other type of damage or loss.
This limited warranty and any disputes arising out of or in connection with this limited warranty ("Disputes") shall be
governed by the laws of the State of Utah, USA, excluding conflicts of law principles and excluding the Convention for the
International Sale of Goods. The courts located in the State of Utah, USA, shall have exclusive jurisdiction over any
Disputes.
This limited warranty gives you specific legal rights, and you may also have other rights, which vary from state to state
and jurisdiction to jurisdiction, and which shall not be affected by this limited warranty. This warranty extends only to
you and cannot by transferred or assigned. If any provision of this limited warranty is unlawful, void or unenforceable,
that provision shall be deemed severable and shall not affect any remaining provisions. In case of any inconsistency
between the English and other versions of this limited warranty, the English version shall prevail.
This warranty cannot be changed, assumed, or amended by any other person or agreement.
APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA
TEL: [phone] | FAX: [phone] | WEB: APOGEEINSTRUMENTS.COM
Copyright © 2020 Apogee Instruments, Inc.