OWNER’S MANUALQUANTUM SENSOR
Model JSQ-421(including SS Model)

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TABLE OF CONTENTS
Owner’s Manual ................................................................................................................................................................................................................ 1
Certificate of Compliance .................................................................................................................................................................................... 3
Introduction ............................................................................................................................................................................................................. 4
Sensor Models ......................................................................................................................................................................................................... 5
Specifications........................................................................................................................................................................................................... 6
Deployment and Installation .............................................................................................................................................................................. 9Operation and Measurement ........................................................................................................................................................................... 11久德電子

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CERTIFICATE OF COMPLIANCE
EU Declaration of Conformity

for the following product(s):Models: JSQ-421
Type: Quantum Sensor
The object of the declaration described above is in conformity with the relevant Union harmonization legislation:
2014/30/EU
2011/65/EU

Electromagnetic Compatibility (EMC) Directive
Restriction of Hazardous Substances (RoHS 2) Directive

Standards referenced during compliance assessment:
EN 61326-1:2013
EN 50581:2012

Electrical equipment for measurement, control and laboratory use – EMC requirements
Technical documentation for the assessment of electrical and electronic products with respect to therestriction 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 cadmium, hexavalent chromium, lead,
mercury, polybrominated biphenyls (PBB), polybrominated diphenyls (PBDE).
Further note that Apogee Instruments does not specifically run any analysis on our raw materials or end products for thepresence of these substances, but rely on the information provided to us by our material suppliers.

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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 fluxin 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 (oneEinstein = 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 thesame 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 thismanual 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 sameenvironments.
Apogee Instruments JSQ 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. JSQ-421 model sensors output a digital signal using SDI-12 communication protocol.

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SENSOR MODELSThis manual covers the SDI-12 communication protocol, original quantum sensor model JSQ-421. Additional models arecovered in their respective manuals.

Model

SignalCalibration

JSQ-421

SDI-12Sunlight and Electric light

JSQ-110

Self-powered

Sunlight

JSQ-120

Self-powered

Electric light

JSQ-311

Self-powered

Sunlight

JSQ-321

Self-powered

Electric light

JSQ-313

Self-powered

Sunlight

JSQ-323

Self-powered

Electric light

JSQ-316

Self-powered

Sunlight

JSQ-326

Self-powered

Electric light

JSQ-2120-2.5 V

Sunlight

JSQ-2220-2.5 VElectric light

JSQ-214

4-20 mA

Sunlight

JSQ-224

4-20 mA

Electric light

JSQ-215

0-5 V

Sunlight

JSQ-225

0-5 V

Electric light

JSQ-420

USB

Sunlight and Electric light

JSQ-422

ModBusSunlight and Electric light

Sensor model number and serial number are locatednear the pigtail leads on the sensor cable. If you
need the manufacturing date of your sensor, pleasecontact Apogee Instruments with the serial numberof your sensor.

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SPECIFICATIONSJSQ--421
Input Voltage Requirement
Current Drain
Calibration Uncertainty
Measurement Repeatability
Long-term Drift(Non-stability)
Non-linearity
Response Time
Field of View
Spectral Range
Directional (Cosine) Response

5.5 to 24 V DC
0.6 mA (quiescent), 1.3 mA (active)± 5 % (see Calibration Traceability below)
Less than 1 %Less than 2 % per year
Less than 1 % (up to 4000 µmol m-2 s-1)
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
180º
410 to 655 nm (wavelengths where response is greater than 50% of maximum; see Spectral Response
below)± 5 % at 75º 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
Mass
Cable

44.0 mm height, 23.5 mm diameter
117 g (with 5 m cable)
5 m of two conductor, shielded, twisted-pair wire, additional cable available in multiples of 5 m;
santoprene rubber jacket (high water resistance, high UV stability, flexibility in cold conditions); pigtail
lead wires

Calibration Traceability
Apogee JSQ original quantum sensor series are calibrated through side-by-side comparison to the mean of four Apogeemodel JSQ-110 or JSQ-120 transfer standard quantum sensors under high output T5 cool white fluorescent lamps. The transfer
standard quantum sensors are calibrated through side-by-side comparison to the mean of at least three LI-COR model LI190R reference quantum sensors under high output T5 cool white fluorescent lamps. The reference quantum sensors arerecalibrated on a biannual schedule with a LI-COR model 1800-02 Optical Radiation Calibrator using a 200 W quartz halogen
lamp. The 1800-02 and quartz halogen lamp are traceable to the National Institute of Standards and Technology (NIST).

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7Spectral Response

Mean spectral response of six JSQ original
quantum series sensors (error bars represent
two standard deviations above and belowmean) compared to PPFD weighting function.
Spectral response measurements were made at
10 nm increments across a wavelength range of
300 to 800 nm in a monochromator with anattached electric light source. Measured spectral
data from each quantum sensor were normalized
by the measured spectral response of themonochromator/electric light combination,
which was measured with a spectroradiometer.

Temperature Response

Mean temperature response of eight JSQ original
quantum series sensors (errors bars represent
two standard deviations above and belowmean). Temperature response measurements
were made at 10 C intervals across a temperature
range of approximately -10 to 40 C in atemperature controlled chamber under a fixed,
broad spectrum, electric lamp. At eachtemperature set point, a spectroradiometer wasused to measure light intensity from the lamp
and all quantum sensors were compared to thespectroradiometer. The spectroradiometer was
mounted external to the temperature control
chamber and remained at room temperatureduring the experiment.

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8Cosine Response

Directional, or cosine, response is defined as themeasurement error at a specific angle of radiation
incidence. Error for Apogee JSQ original quantum series
sensors is approximately ± 2 % and ± 5 % at solar zenith
angles of 45° and 75°, respectively.

Mean cosine response of twenty-three JSQ
original quantum series sensors (error
bars represent two standard deviations
above and below mean). Cosine response
measurements were made by direct sideby-side comparison to the mean of fourreference thermopile pyranometers, withsolar zenith angle-dependent factors
applied to convert total shortwave
radiation to PPFD. Blue points represent
the AM response and red points represent
the PM response.

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DEPLOYMENT AND INSTALLATION
Mount the sensor to a solid surface with the nylon mounting screw provided. To accurately measure PPFD incident on ahorizontal 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.

Nylon Screw: 10-32 x 3/8

Nylon Screw: 10-32 x 3/8

Model AL-100

Model AL-120

To minimize azimuth error, the sensor should be mounted with the cable pointing toward true north in the northernhemisphere or true south in the southern hemisphere. Azimuth error is typically less than 1 %, but it is easy to minimize byproper 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, thegreen 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.

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Cable Connectors
Apogee started offering in-line cable connectors on somebare-lead sensors in March 2018 to simplify the process ofremoving sensors from weather stations for calibration by
not requiring the full cable to be uninstalled back to the datalogger.
The ruggedized M8 connectors are rated IP67, made ofcorrosion-resistant marine-grade stainless-steel, anddesigned for extended use in harsh environmental
conditions.

Inline cable connectors are installed 30 cm from the head(pyranometer pictured)

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 data logger end of the cable.
If you ever need a replacement cable, please contact us
directly to ensure ordering the proper pigtail configuration.
Alignment: When reconnecting your sensor, arrows on theconnector 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 thestation from water and dirt with electrical tape or othermethod.

Tightening: Connectors are designed to be firmly fingertightened only. There is an o-ring inside the connector thatcan be overly compressed if a wrench is used. Pay attention
to thread alignment to avoid cross-threading. When fullytightened, 1-2 threads may still be visible.

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A reference notch inside the connector ensuresproper alignment before tightening.

When sending sensors in for calibration, only send the shortend of the cable and half the connector.

Finger-tighten firmly

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OPERATION AND MEASUREMENTThe JSQ-421 quantum sensor has a SDI-12 output, where shortwave radiation is returned in digital format. Measurement of
JSQ-421 quantum sensors requires a measurement device with SDI-12 functionality that includes the M or C command.

VERY IMPORTANT: Apogee changed all wiring colors of our bare-lead sensors in March 2018 in conjunction
with the release of inline cable connectors on some sensors. To ensure proper connection to your data device,please note your serial number or if your sensor has a stainless-steel connector 30 cm from the sensor head thenuse the appropriate wiring configuration below.
Wiring for JSQ-421 Serial Numbers within the range 0-2052

Red: Power In (4.5-24 V DC)
Black: SDI-12 Data Line
Clear: Ground (shield wire)

Wiring for JSQ-421 Serial Numbers 2053 and above or with a cable connector

Black: Ground
Red:

Power In (5.5-24 V DC)

White: SDI-12 Data Line
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Sensor Calibration
All Apogee SDI-12 JSQ-400 series quantum sensors have sensor-specific calibration coefficients determined during thecustom calibration process. Coefficients are programmed into the microcontrollers at the factory.
SDI-12 Interface
The following is a brief explanation of the serial digital interface SDI-12 protocol instructions used in Apogee JSQ-421
quantum sensors. For questions on the implementation of this protocol, please refer to the official version of the SDI-12
protocol: http://www.sdi-12.org/specification.php (version 1.4, August 10, 2016).
Overview
During normal communication, the data recorder sends a packet of data to the sensor that consists of an address and acommand. Then, the sensor sends a response. In the following descriptions, SDI-12 commands and responses are enclosed inquotes. The SDI-12 address and the command/response terminators are defined as follows:
Sensors come from the factory with the address of “0” for use in single sensor systems. Addresses “1 to 9” and “A toZ”, or “a to z”, can be used for additional sensors connected to the same SDI-12 bus.
“!” is the last character of a command instruction. In order to be compliant with SDI-12 protocol, all commands must be
terminated with a “!”. SDI-12 language supports a variety of commands. Supported commands for the Apogee Instruments
JSQ-421 quantum sensors are listed in the following table (“a” is the sensor address. The following ASCII Characters are valid
addresses: “0-9” or “A-Z”).
Supported Commands for Apogee Instruments JSQ-421 Quantum Sensors

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Instruction Name
Acknowledge Active Command

Instruction Syntaxa!

Send Identification CommandaI!

Responds with sensor information

Measurement Command
Measurement Command w/ Check
Character
Change Address Command

aM!
aMC!

Concurrent Measurement CommandaC!

Concurrent Measurement Command w/
Check Character

aCC!

Address Query Command?!

Get Data Command

aD0!

Tells the sensor to take a measurement
Tells the sensor to take a measurement and return itwith a check character
Changes the sensor address from a to b
Used to take a measurement when more than one
sensor is used on the same data line
Used to take a measurement when more than one
sensor is used on the same data line. Data is returned
with a check character.
Used when the address is unknown to have the sensor
identify its address, all sensors on data line respond
Retrieves the data from a sensor

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aAb!

Description
Responds if the sensor with address a is on the line

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13Make Measurement Command: M!
The make measurement command signals a measurement sequence to be performed. Data values generated in response tothis command are stored in the sensor's buffer for subsequent collection using “D” commands. Data will be retained in sensor
storage until another “M”, “C”, or “V” command is executed. M commands are shown in the following examples:
CommandaM! or aM0!
aM1!
aM2!
aM3!

Response
a0011<cr><If>a0011<cr><If>a0011<cr><If>a0011<cr><If>

aMC0!
aMC1!
aMC2!
aMC3!

a0011<cr><If>a0011<cr><If>a0011<cr><If>a0011<cr><If>

Response to 0D0!
Returns µmol m-2 s-1 using electric light calibration
Returns millivolt output
Returns µmol m-2 s-1 using sunlight calibration
Returns immersed µmol m-2 s-1 for underwater measurements with electric lightcalibration
Returns µmol m-2 s-1 using electric light calibration w/CRC
Returns millivolt output w/ CRC
Returns µmol m-2 s-1 using sunlight calibration w/ CRC
Returns immersed µmol m-2 s-1 for underwater measurements with electric lightcalibration w/ CRC

where a is the sensor address (“0-9”, “A-Z”, “a-z”) and M is an upper-case ASCII character.
The data values are separated by the sign “+”, as in the following example (0 is the address):
Command
0M0!
0D0!
0M1!
0D0!
0M2!
0D0!
0M3!
0D0!

Sensor Response
00011<cr><lf>
0+2000.0<cr><lf>00011<cr><lf>
0+400.0<cr><lf>00011<cr><If>
0+2000.0<cr><If>00011<cr><If>
0+2000.0<cr><If>

Sensor Response when data is ready0<cr><lf>0<cr><lf>0<cr><If>
0<cr><If>where 2000.0 is µmol m-2 s-1 and 400.0 is mV.
Concurrent Measurement Command: aC!
A concurrent measurement is one which occurs while other SDI-12 sensors on the bus are also making measurements. This
command is similar to the “aM!” command, however, the nn field has an extra digit and the sensor does not issue a service
request when it has completed the measurement. Communicating with other sensors will NOT abort a concurrent
measurement. Data values generated in response to this command are stored in the sensor's buffer for subsequent collection
using “D” commands. The data will be retained in the sensor until another “M”, “C”, or “V” command is executed:
CommandaC! or aC0!
aC1!
aC2!
aC3!

Response
a00101<cr><lf>a00101<cr><lf>a00101<cr><lf>a00101<cr><lf>

aCC! or aCC0!
aCC1!
aCC2!
aCC3!

a00101<cr><lf>a00101<cr><lf>a00101<cr><lf>a00101<cr><lf>

Response to 0D0!
Returns µmol m-2 s-1 using electric light calibration
Returns millivolt output
Returns µmol m-2 s-1 using sunlight calibration
Returns immersed µmol m-2 s-1 for underwater measurements with electric
light calibration
Returns µmol m-2 s-1 using electric light calibration w/CRC
Returns millivolt output w/CRC
Returns µmol m-2 s-1 using sunlight calibration w/CRC
Returns immersed µmol m-2 s-1 for underwater measurements with electric
light calibration w/CRC

where a is the sensor address (“0-9”, “A-Z”, “a-z”, “*”, “?”) and C is an upper-case ASCII character.

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For example (0 is the address):
Command
0C0!
0D0!
0C1!
0D0!
0C2!
0D0!
0C3!
0D0!

Sensor Response
000101<cr><lf>
0+2000.0<cr><lf>000101<cr><If>
0+400.0<cr><If>000101<cr><lf>
0+2000.0<cr><lf>000101<cr><If>
0+2000.0<cr><If>

where 2000.0 is µmol m-2 s-1 and 400.0 is mV.
Change Sensor Address: aAb!
The change sensor address command allows the sensor address to be changed. If multiple SDI-12 devices are on the samebus, each device will require a unique SDI-12 address. For example, two SDI-12 sensors with the factory address of 0 requires
changing the address on one of the sensors to a non-zero value in order for both sensors to communicate properly on thesame channel:
CommandaAb!

Responseb<cr><lf>Description
Change the address of the sensor

where a is the current (old) sensor address (“0-9”, “A-Z”), A is an upper-case ASCII character denoting the instruction forchanging the address, b is the new sensor address to be programmed (“0-9”, “A-Z”), and ! is the standard character to executethe command. If the address change is successful, the datalogger will respond with the new address and a <cr><lf>.
Send Identification Command: aI!
The send identification command responds with sensor vendor, model, and version data. Any measurement data in thesensor's buffer is not disturbed:
Command"aI!"

Response
a13Apogee JSQ-421vvvxx…xx<cr><lf>

Description
The sensor serial number and other identifying values are
returned

where a is the sensor address (“0-9”, “A-Z”, “a-z”, “*”, “?”), 421 is the sensor model number, vvv is a three character field
specifying the sensor version number, and xx...xx is serial number.

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Metadata Commands
Identify Measurement Commands
The Identify Measurement Commands can be used to view the command response without making a measurement. The
command response indicates the time it takes to make the measurement and the number of data values that it returns. It
works with the Verification Command (aV!), Measurement Commands (aM!, aM1! … aM9!, aMC!, aMC1! … aMC9!), andConcurrent Measurement Commands (aC!, aC1! … aC9! , aCC!, aCC1! … aCC9!).
The format of the Identify Measurement Command is the address, the capital letter I, the measurement command, and thecommand terminator (“!”), as follows:<address>I<command>!
The format of the response is the same as if the sensor is making a measurement. For the Verification Command andMeasurement Commands, the response is atttn<CR><LF>. For the C Command, it is atttnn<CR><LF>. For the High Volume
Commands, it is atttnnn<CR><LF>. The address is indicated by a, the time in seconds to make the measurement is indicatedby ttt, and the number of measurements is indicated by n, nn, and nnn. The response is terminated with a Carriage Return(<CR>) and Line Feed (<LF>).
Identify Measurement Command example:
3IMC2!

The Identify Measurement Command for sensor address 3, M2 command, requesting a CRC.

30032<CR><LF>

The response from sensor address three indicating that the measurement will take threeseconds and two data values will be returned.

Identify Measurement Parameter Commands
The Measurement Parameter Commands can be used to retrieve information about each data value that a command returns.
The first value returned is a Standard Hydrometeorological Exchange Format (SHEF) code. SHEF codes are published by the
National Oceanic and Atmospheric Administration (NOAA). The SHEF code manual can be foundat http://www.nws.noaa.gov/oh/hrl/shef/indexshef.htm. The second value is the units of the parameter. Additional fields
with more information are optional.
The Measurement Parameter Commands work with the Verification Command (aV!), Measurement Commands (aM!, aM1! …
aM9!, aMC!, aMC1! … aMC9!), and Concurrent Measurement Commands (aC!, aC1! … aC9! , aCC!, aCC1! … aCC9!).
The format of the Identify Measurement Parameter Command is the address, the capital letter I, the measurement command,the underscore character (“_”), a three-digit decimal number, and the command terminator (“!”). The three-digit decimal
indicates which number of measurement that the command returns, starting with “001” and continuing to “002” and so on,
up to the number of measurements that the command returns.
<address>I<command>_<three-digit decimal>!
The format of the response is comma delimited and terminated with a semicolon. The first value is the address. The second
value is the SHEF code. The third value is the units. Other optional values may appear, such as a description of the data value.
The response is terminated with a Carriage Return (<CR>) and Line Feed (<LF>).

a,<SHEF Code>,<units>;<CR><LF>

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Identify Measurement Parameter Command example:
1IC_001!
1,RW,Watts/meter squared,incoming solar radiation;<CR><LF>

The Identify Measurement Parameter Commandfor sensor address 1, C command, data value 1.
The response from sensor address 1, SHEF code
RW, units of Watts/meter squared, and additional
information of incoming solar radiation.

Sunlight and Electric light Calibration
Apogee JSQ-421 quantum sensors are calibrated to measure PPFD for both sunlight and electric light. The difference between
the calibrations is 12 %. The electric light calibration (calibration source is T5 cool white fluorescent lamps) will readapproximately 12 % low in sunlight. The aM!, aMC!, aC!, or aCC! commands return the sensor PPFD measurement with electric
light calibration. The aM2!, aMC2!, aC2!, or aCC2! commands return the sensor PPFD measurement with sunlight calibration.
Spectral Errors and Yield Photon Flux Measurements
In addition to PPFD measurements, Apogee JSQ series quantum sensors can also be used to measure yield photon flux
density (YPFD): photon flux density weighted according to plant photosynthetic efficiency (McCree, 1972) and summed.
YPFD is also expressed in units of µmol m-2 s-1, and is similar to PPFD, but has been reported to be more closely correlated tophotosynthesis than PPFD in some studies. PPFD is usually measured and reported because the PPFD spectral weighting
function (equal weight given to all photons between 400 and 700 nm; no weight given to photons outside this range) is
easier to define and measure, and as a result, PPFD is widely accepted. The calibration factor for YPFD is 4.50 and 4.45 µmol
m-2 s-1 per mV for sunlight and electric light measurements, respectively.
The weighting functions for PPFD and YPFD are shown in the graph below, along with the spectral response of Apogee JSQ
series quantum sensors. The closer the spectral response matches the defined PPFD or YPFD spectral weighting functions,the smaller spectral errors will be. The table below provides spectral error estimates for PPFD and YPFD measurements fromlight sources different than the calibration source. The method of Federer and Tanner (1966) was used to determine spectral
errors based on the PPFD and YPFD spectral weighting functions, measured sensor spectral response, and radiation source
spectral outputs (measured with a spectroradiometer). This method calculates spectral error and does not consider
calibration, cosine, and temperature errors.
Federer, C. A., and C. B. Tanner, 1966. Sensors for measuring light available for photosynthesis. Ecology 47:654-657.
McCree, K. J., 1972. The action spectrum, absorptance and quantum yield of photosynthesis in crop plants. Agricultural
Meteorology 9:191-216.

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17

Radiation weighting factors for PPFD (defined plant
response to radiation), YPFD (measured plant
response to radiation), and Apogee JSQ Series
quantum sensors (sensor sensitivity to different
wavelengths of radiation).
JSQ Series

Spectral Errors for PPFD and YPFD Measurements with Apogee JSQ Series Quantum Sensors
Radiation Source (Error Calculated Relative to Sun, Clear Sky)Sun (Clear Sky)Sun (Cloudy Sky)
Reflected from Grass Canopy
Reflected from Deciduous Canopy
Reflected from Conifer Canopy
Transmitted below Grass Canopy
Transmitted below Deciduous Canopy
Transmitted below Conifer Canopy
Radiation Source (Error Calculated Relative to Cool White Fluorescent, T5)
Cool White Fluorescent (T5)
Cool White Fluorescent (T8)
Cool White Fluorescent (T12)Compact Fluorescent
Metal Halide
Ceramic Metal Halide
High Pressure Sodium
Blue LED (448 nm peak, 20 nm full-width half-maximum)
Green LED (524 nm peak, 30 nm full-width half-maximum)
Red LED (635 nm peak, 20 nm full-width half-maximum)
Red, Blue LED Mixture (85 % Red, 15 % Blue)
Red, Green, Blue LED Mixture (72 % Red, 16 % Green, 12 % Blue)
Cool White Fluorescent LED
Neutral White Fluorescent LED
Warm White Fluorescent LED

PPFD Error [%]
0.0
1.4
5.7
4.9
5.5
6.4
6.8
5.3

YPFD Error [%]
0.0
1.6
-6.3
-7.0
-6.8
-4.5
-5.4
2.6

0.0
-0.3
-1.4
-0.5
-3.7
-6.0
0.8
-12.7
8.0
4.8
2.4
3.4
-4.6
-6.7
-10.9

0.0
-1.2
-2.0
-5.3
-3.7
-6.4
-7.2
8.0
26.2
-6.2
-4.4
0.2
-0.6
-5.2
-13.0

Quantum sensors can be a very practical means of measuring PPFD and YPFD from multiple radiation sources, but spectral
errors must be considered. The spectral errors in the table above can be used as correction factors for individual radiation
sources.
Underwater Measurements and Immersion Effect
When a quantum sensor that was calibrated in air is used to make underwater measurements, the sensor reads low. Thisphenomenon is called the immersion effect and happens because the refractive index of water (1.33) is greater than air(1.00). The higher refractive index of water causes more light to be backscattered (or reflected) out of the sensor in water
than in air (Smith,1969; Tyler and Smith,1970). As more light is reflected, less light is transmitted through the diffuser to thedetector, which causes the sensor to read low. Without correcting for this effect, underwater measurements are only relative,
which makes it difficult to compare light in different environments.

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TEL:+886-4-23729418

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18
The JSQ-400 series sensors have an immersion effect correction factor of 1.08. The immersion effect correction factor is
automatically applied to the sensor measurement when using the aM3!, aMC3!, aC3!, and aCC3! commands. These
commands return an electric light calibration PPFD value that has been multiplied by the immersion effect correction factorof 1.08. The immersion effect correction factor will need to be multiplied to all other measurement and concurrent
commands when the sensor is used for underwater measurements.

久德電子

TEL:+886-4-23729418

FAX:+886-4-23724011 (40349)台中市西區福人街11號

www.jetec.com.tw