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Apogee Instruments SQ-514, Owner'S Manual, Page: 11 / 20

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Apogee Instruments SQ-514 Owner'S Manual Download Page 11

OPERATION AND MEASUREMENT 

Connect the sensor to a measurement device (meter, datalogger, controller) capable of measuring and displaying a 
4-20 mA signal. To maximize measurement resolution and signal-to-noise ratio, the input range of the 
measurement device should closely match the output range of the quantum sensor. 

DO NOT connect the sensor 

to a power source greater than 24 V DC. 
 

 

 

 

 

 

 

Sensor Calibration 

Apogee SQ-514 sensors have a standard PPFD calibration factor of exactly: 

250.0 µmol m

-2

 s

-1

 per mA

 

Multiply this calibration factor by the measured mA signal to convert to PPFD in units of µmol m

-2

 s

-1

: 

Calibration Factor (250 µmol m

-2

 s

-1

 per mA) * Sensor Output Signal (mA) = PPFD (µmol m

-2

 s

-1

) 

      250                            *                      (12    

–

    4) 

             =            2000 

  

 

 

 

 

 

 

 

Example of PPFD measurement with an Apogee SQ-514 
quantum sensor. Full sunlight yields a PPFD on a horizontal 

plane at the Earth’s surface of approximately 2000 µmol 

  

m

-2

 s

-1

. This yields an output signal of 12 mA. The signal is 

converted to PPFD by subtracting the 4.0 mA offset and 
then multiplying by the calibration factor of 250 µmol        
m

-2

 s

-1

 per mA. 

 

Sensor Output 

12 mA 

White: 4-20 mA signal output 

Red: Input power (7-24 V DC) 

Black: Ground (for sensor signal and input power) 

Clear: Shield/Ground 

Full Sunlight 

(2000 µmol m

-2

s

-1

) 

Summary of Contents for SQ-514

Page 1: ...STRUMENTS INC 721 WEST 1800 NORTH LOGAN UTAH 84321 USA TEL 435 792 4700 FAX 435 787 8268 WEB APOGEEINSTRUMENTS COM Copyright 2021 Apogee Instruments Inc OWNER S MANUAL QUANTUM SENSOR Model SQ 514 Rev 28 Oct 2020 ...

Page 2: ...e of Compliance 3 Introduction 4 Sensor Models 5 Specifications 6 Deployment and Installation 9 Cable Connectors 10 Operation and Measurement 10 Maintenance and Recalibration 16 Troubleshooting and Customer Support 18 Return and Warranty Policy 19 ...

Page 3: ...ctrical 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 di...

Page 4: ...unit time only PPFD is used in this manual Sensors that measure PPFD are often called quantum sensors due to the quantized nature of radiation A quantum refers to the minimum quantity of radiation one photon involved in physical interactions e g absorption by photosynthetic pigments In other words one photon is a single quantum of radiation Typical applications of quantum sensors include measureme...

Page 5: ...ed voltage output quantum sensor model SQ 514 listed in bold below Additional models are covered in their respective manuals Model Signal SQ 514 4 20 mA SQ 500 Self powered SQ 512 0 2 5 V SQ 515 0 5 V SQ 520 USB SQ 521 SDI 12 SQ 522 Modbus Serial Number 0 3353 Sensor model number and serial number are located near the pigtail leads on the sensor cable If you need the manufacturing date of your sen...

Page 6: ...al Range 389 to 692 nm 5 nm wavelengths where response is greater than 50 Spectral Selectivity Less than 10 from 412 to 682 5 nm see Spectral Response below Directional Cosine Response 2 at 45 zenith angle 5 at 75 zenith angle see Directional Response below Azimuth Error Less than 0 5 Tilt Error Less than 0 5 Temperature Response 0 11 0 04 per C see Temperature Response below Uncertainty in Daily ...

Page 7: ... all quantum sensors were compared to the spectroradiometer The spectroradiometer was mounted external to the temperature control chamber and remained at room temperature during the experiment Mean spectral response measurements of six replicate Apogee SQ 100 original and SQ 500 full spectrum series quantum sensors Spectral response measurements were made at 10 nm increments across a wavelength ra...

Page 8: ... quantum sensors from the mean of replicate reference quantum sensors LI COR models LI 190 and LI 190R Kipp Zonen model PQS 1 Data were also collected in the laboratory using a reference lamp and positioning the sensor at varying angles Directional cosine response is defined as the measurement error at a specific angle of radiation incidence Error for Apogee SQ 500 series quantum sensors is approx...

Page 9: ...ng 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...

Page 10: ... 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...

Page 11: ... calibration factor by the measured mA signal to convert to PPFD in units of µmol m 2 s 1 Calibration Factor 250 µmol m 2 s 1 per mA Sensor Output Signal mA PPFD µmol m 2 s 1 250 12 4 2000 Example of PPFD measurement with an Apogee SQ 514 quantum sensor Full sunlight yields a PPFD on a horizontal plane at the Earth s surface of approximately 2000 µmol m 2 s 1 This yields an output signal of 12 mA ...

Page 12: ...ric lamps cool white fluorescent metal halide high pressure sodium but larger errors for different mixtures of light emitting diodes LEDs for the SQ 100 series sensors Spectral errors for the SQ 500 series sensors are smaller than those for SQ 100 series sensors because the spectral response of SQ 500 series sensors is a closer match to the defined plant photosynthetic response Quantum sensors are...

Page 13: ...s grown in growth chambers was similar but there were differences particularly at shorter wavelengths less than 450 nm There was also some variability between species McCree 1972a Inada 1976 McCree 1972b found that equally weighting all photons between 400 and 700 nm and summing the result defined as photosynthetic photon flux density PPFD in units of mol m 2 s 1 was well correlated to photosynthe...

Page 14: ... M D Clegg 1971 Photosynthesis light sensor and meter Ecology 52 125 131 Federer C A and C B Tanner 1966 Sensors for measuring light available for photosynthesis Ecology 47 654 657 Inada K 1976 Action spectra for photosynthesis in higher plants Plant and Cell Physiology 17 355 365 McCree K J 1972a The action spectrum absorptance and quantum yield of photosynthesis in crop plants Agricultural Meteo...

Page 15: ...factors can be derived by making measurements in air and at multiple water depths at a constant distance from a lamp in a controlled laboratory setting Apogee SQ 500 series quantum sensors have an immersion effect correction factor of 1 32 This correction factor should be multiplied by PPFD measurements made underwater to yield accurate PPFD Further information on underwater measurements and the i...

Page 16: ... every two years although you can often wait longer according to your particular tolerances To determine if a specific sensor needs recalibration the Clear Sky Calculator www clearskycalculator com website and or smartphone app can be used to indicate PPFD incident on a horizontal surface at any time of day at any location in the world It is most accurate when used near solar noon in spring and su...

Page 17: ...rs are available one for quantum sensors PPFD and one for pyranometers total shortwave radiation Clear Sky Calculator for quantum sensors Site data are input in blue cells in middle of page and an estimate of PPFD is returned on right hand side of page ...

Page 18: ...ive a maximum load of 500 Ω RL 12 V 2 V 0 02 A 500 Ω The output voltage from the sensor is calculated by adding the wire resistance to the input resistance of the data collection system and then multiplying by 0 02 A Cable Length Shortening or splicing on additional cable in the field is generally not a problem for the current output of the SQ 514 However adding cable will result in a greater resi...

Page 19: ...r 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 o...

Page 20: ...anship 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 PRODUCTS BEYOND THE WARRANTY PERIOD For issues with sensors beyond the warranty period please contact Apogee at techsupport apogeeinstruments com to discuss repair or replacement options OTH...

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