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Summary of Contents for Apogee Instruments SQ-422
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Page 1: Owner's Manual
OWNER’S MANUAL QUANTUM SENSOR Model SQ-422 APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA TEL: (435) 792-4700 | FAX: (435) 787-8268 | WEB: APOGEEINSTRUMENTS.COM Copyright © 2020 Apogee Instruments, Inc. -
Page 2: Table Of Contents
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 ............................. 20 Troubleshooting and Customer Support .......................... -
Page 3: Certificate Of Compliance
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. -
Page 4: Introduction
Sensors are potted solid with no internal air space, and are designed for continuous PPFD measurement in indoor or outdoor environments. The SQ-422 model outputs a digital signal using Modbus RTU communication protocol over RS-232 or RS-485. -
Page 5: Sensor Models
SENSOR MODELS This manual covers the Modbus RTU communication protocol, original quantum sensor model SQ-422 (in bold below). Additional models are covered in their respective manuals. Model Signal Calibration Sunlight and Electric SQ-422 Modbus light SQ-110 Self-powered Sunlight SQ-120 Self-powered... -
Page 6: Specifications
SPECIFICATIONS SQ-422 Input Voltage Requirement 5.5 to 24 V DC RS-232 quiescent 36.87 mA, active 37.06 mA; Average Max Current Draw RS-485 quiescent 37.37 mA, active 42.30 mA Calibration Uncertainty ± 5 % (see Calibration Traceability below) Measurement Repeatability Less than 1 %... - Page 7 Spectral Response Mean spectral response of six SQ-100 series quantum sensors (error bars represent two standard deviations above and below mean) compared to defined plant response to photons. Spectral response measurements were made at 10 nm increments across a wavelength range of 300 to 800 nm with a monochromator and an attached electric light source.
- Page 8 Cosine Response Directional (cosine) response is defined as the measurement error at a specific angle of radiation incidence. Error for Apogee SQ-100 series quantum sensors is approximately ± 2 % and ± 5 % at solar zenith angles of 45° and 75°, respectively.
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Page 9: 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. -
Page 10: Cable Connectors
CABLE CONNECTORS Apogee started offering cable connectors on some bare-lead sensors in March 2018 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). -
Page 11: Operation And Measurement
OPERATION AND MEASUREMENT The SQ-422 quantum sensor has a Modbus output, where photosynthetic photon flux density (PPFD) is returned in digital format. Measurement of SQ-422 quantum sensors requires a measurement device with a Modbus interface that supports the Read Holding Registers (0x03) function. - Page 12 Register Index Each register in a sensor represents a value in the sensor, such as a measurement or a configuration parameter. Some registers can only be read, some registers can only be written, and some can be both read and written. Each register exists at a specified index in the table for the sensor.
- Page 13 Read only registers (function code 0x3). Float Registers calibrated output µmol m⁻² s⁻¹ detector millivolts immersed output µmol m⁻² s⁻¹ solar output µmol m⁻² s⁻¹ orientation – angle from vertical (degrees) device status (1 means device is busy, 0 otherwise) firmware version Integer Registers calibrated output µmol m⁻²...
- Page 14 *Registers marked with an asterisk (*) cannot be written to unless a specific procedure is followed. Contact Apogee Instruments to receive the procedure for writing these registers. Write only registers (function code 0x10). Integer Registers Writing to this register resets Coefficients to firmware defaults.
- Page 15 Packet Framing: Apogee sensors use Modbus RTU packets and tend to adhere to the following pattern: Slave Address (1 byte), Function Code (1 byte), Starting Address (2 bytes), Number of Registers (2 bytes), Data Length (1 byte, optional) Data (n bytes, optional) Modbus RTU packets use the zero-based address when addressing registers.
- Page 16 Spectral Error The combination of diffuser transmittance, interference filter transmittance, and photodetector sensitivity yields spectral response of a quantum sensor. A perfect photodetector/filter/diffuser combination would exactly match the defined plant photosynthetic response to photons (equal weighting to all photons between 400 and 700 nm, no weighting of photons outside this range), but this is challenging in practice.
- Page 17 Yield Photon Flux Density (YPFD) Measurements Photosynthesis in plants does not respond equally to all photons. Relative quantum yield (plant photosynthetic efficiency) is dependent on wavelength (green line in figure below) (McCree, 1972a; Inada, 1976). This is due to the combination of spectral absorptivity of plant leaves (absorptivity is higher for blue and red photons than green photons) and absorption by non-photosynthetic pigments.
- Page 18 Correlation between photosynthetic photon flux density (PPFD) and yield photon flux density (YPFD) for multiple different radiation sources. YPFD is approximately 90 % of PPFD. Measurements were made with a spectroradiometer (Apogee Instruments model PS-200) and weighting factors shown in the previous figure were used to calculate PPFD and YPFD.
- Page 19 Immersion Effect Correction Factor When a radiation sensor is submerged in water, more of the incident radiation is backscattered out of the diffuser than when the sensor is in air (Smith, 1969; Tyler and Smith, 1970). This phenomenon is caused by the difference in the refractive index for air (1.00) and water (1.33), and is called the immersion effect.
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Page 20: Maintenance And Recalibration
3. Salt deposit accumulation from evaporation of sea spray or sprinkler irrigation water. Apogee Instruments quantum 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. - Page 21 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.
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Page 22: Troubleshooting And Customer Support
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 37 mA when the sensor is powered. Any current drain significantly greater than approximately 37 mA indicates a problem with power supply to the sensors, wiring of the sensor, or sensor electronics. -
Page 23: Return And Warranty Policy
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... - Page 24 84321, USA 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.
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