OWNER’S MANUAL QUANTUM SENSOR Model SQ-421 (including SS Model) APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA TEL: (435) 792-4700 | FAX: (435) 787-8268 | WEB: APOGEEINSTRUMENTS.COM Copyright © 2019 Apogee Instruments, Inc.
TABLE OF CONTENTS Owner’s Manual ............................................................................................................................................................................... 1 Certificate of Compliance ......................................................................................................................................................... 3 Introduction ..........................................................................................................
CERTIFICATE OF COMPLIANCE EU Declaration of Conformity This declaration of conformity is issued under the sole responsibility of the manufacturer: 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 often expressed as photosynthetic photon flux density (PPFD): photon flux 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).
SENSOR MODELS This manual covers the SDI-12 communication protocol, original quantum sensor model SQ-421. Additional models are covered in their respective manuals.
SPECIFICATIONS SQ--421 Input Voltage Requirement Current Drain Calibration Uncertainty Measurement Repeatability Long-term Drift (Non-stability) Non-linearity Response Time Field of View Spectral Range 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.
Spectral Response Mean spectral response of six SQ original quantum series sensors (error bars represent two standard deviations above and below mean) 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 an attached electric light source.
Cosine Response Directional, or cosine, response is defined as the measurement error at a specific angle of radiation incidence. Error for Apogee SQ original quantum series sensors is approximately ± 2 % and ± 5 % at solar zenith angles of 45° and 75°, respectively. Mean cosine response of twentythree SQ original quantum series sensors (error bars represent two standard deviations above and below mean).
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.
CABLE CONNECTORS Apogee started offering in-line cable connectors on some bare-lead sensors in March 2018 to simplify the process of removing sensors from weather stations for calibration by not requiring the full cable to be uninstalled back to the data logger. The ruggedized M8 connectors are rated IP68, made of corrosion-resistant marine-grade stainless-steel, and designed for extended use in harsh environmental conditions.
OPERATION AND MEASUREMENT The SQ-421 quantum sensor has a SDI-12 output, where shortwave radiation is returned in digital format. Measurement of SQ-421 quantum sensors requires a measurement device with SDI-12 functionality that includes the M or C command. VERY IMPORTANT: Apogee changed the wiring colors of all our bare-lead sensors in March 2018 in conjunction with the release of inline cable connectors on some sensors.
Sensor Calibration All Apogee SDI-12 SQ-400 series quantum sensors have sensor-specific calibration coefficients determined during the custom 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 SQ421 quantum sensors. For questions on the implementation of this protocol, please refer to the official version of the SDI-12 protocol: http://www.
Make Measurement Command: M! The make measurement command signals a measurement sequence to be performed. Data values generated in response to this 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.
where a is the sensor address (“0-9”, “A-Z”, “a-z”, “*”, “?”) and C is an upper-case ASCII character. For example (0 is the address): Command 0C0! 0D0! 0C1! 0D0! 0C2! 0D0! 0C3! 0D0! Sensor Response 000101 0+2000.0 000101 0+400.0 000101 0+2000.0 000101 0+2000.0 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.
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!), and Concurrent Measurement Commands (aC!, aC1! … aC9! , aCC!, aCC1! … aCC9!).
Identify Measurement Parameter Command example: 1IC_001! 1,RW,Watts/meter squared,incoming solar radiation; The Identify Measurement Parameter Command for 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 SQ-421 quantum sensors are calibrated to measure PPFD for both sunlight and electric light.
Radiation weighting factors for PPFD (defined plant response to radiation), YPFD (measured plant response to radiation), and Apogee SQ Series quantum sensors (sensor sensitivity to different wavelengths of radiation).
Underwater Measurements and Immersion Effect When a quantum sensor that was calibrated in air is used to make underwater measurements, the sensor reads low. This phenomenon 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).
MAINTENANCE AND RECALIBRATION Moisture or debris on the diffuser is a common cause of low readings. The sensor has a domed diffuser and housing for improved self-cleaning from rainfall, but materials can accumulate on the diffuser (e.g., dust during periods of low rainfall, salt deposits from evaporation of sea spray or sprinkler irrigation water) and partially block the optical path. Dust or organic deposits are best removed using water or window cleaner and a soft cloth or cotton swab.
Homepage of the Clear Sky Calculator. Two calculators 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.
TROUBLESHOOTING AND CUSTOMER SUPPORT Independent Verification of Functionality If the sensor does not communicate with the datalogger, use an ammeter to check the current drain. It should be near 0.6 mA when the sensor is not communicating and spike to approximately 1.3 mA when the sensor is communicating. Any current drain greater than approximately 6 mA indicates a problem with power supply to the sensors, wiring of the sensor, or sensor electronics.
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.
Authorization (RMA) number from our technical support department by calling (435) 245-8012 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.
