SP-LITE Silicon Pyranometer Revision: 7/04 C o p y r i g h t © 1 9 9 8 - 2 0 0 4 C a m p b e l l S c i e n t i f i c , I n c .
Warranty and Assistance The SP-LITE SILICON PYRANOMETER is warranted by CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and workmanship under normal use and service for twelve (12) months from date of shipment unless specified otherwise. Batteries have no warranty. CAMPBELL SCIENTIFIC, INC.'s obligation under this warranty is limited to repairing or replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective products.
SP-LITE Table of Contents PDF viewers note: These page numbers refer to the printed version of this document. Use the Adobe Acrobat® bookmarks tab for links to specific sections. 1. General Description.....................................................1 1.1 Electrical Properties..................................................................................1 1.2 Spectral Properties ....................................................................................2 1.3 Directional/Cosine Response.....
SP-LITE Table of Contents Tables 1. Datalogger Connections for Differential Measurement ............................. 7 2. Datalogger Connections for Single-Ended Measurement.......................... 7 3. Multipliers Required for Flux Density and Total Fluxes ...........................
SP-LITE Silicon Pyranometer The SP-LITE measures incoming solar radiation (sun plus sky radiation) with a photodiode detector. Output from the photodiode is a current, which is converted to voltage by an internal shunt resistor. The SP-LITE can be used in solar energy applications such as plant growth, thermal convection and evapotranspiration. 1. General Description FIGURE 1. SP-LITE Sensor without Leveling Fixture The SP-LITE is used for measuring solar radiation.
SP-LITE Silicon Pyranometer FIGURE 2. SP-LITE Electrical Circuit 1.2 Spectral Properties The spectral properties of the SP-LITE are mainly determined by the spectral response of the photodiode, which is shown in Figure 3, below. FIGURE 3. Spectral Sensitivity of Pyranometers Compared with Solar Radiation The SP-LITE is calibrated for solar radiation under clear sky conditions. The spectrum for these conditions, at sea level, is also shown in Figure 3.
SP-LITE Silicon Pyranometer Both the spectral sensitivity and the photodiode sensitivity of the SP-LITE will change with temperature, and the separate effect of each of these changes cannot be easily determined. 1.3 Directional/Cosine Response A perfect cosine response will show maximum sensitivity at an angle of incidence of zero degrees (perpendicular to the sensor surface) and zero sensitivity at an angle of incidence of 90 degrees (radiation passing over the sensor surface).
SP-LITE Silicon Pyranometer 2. Sensor Specifications Electrical <50 Ω <1 second 10 µV/(W m-2) 0 – 15 mV Nominal Impedance: Response Time: Sensitivity: Expected signal range: (under atmospheric conditions) Stability: Non-linearity: Temperature dependence of sensitivity: <±2% per year <±1% up to 1000 W m-2 <±0.
SP-LITE Silicon Pyranometer 3. Installing the SP-LITE The SP-LITE and PN 14282 base/leveling fixture are attached to a tripod or tower using one of two mounting configurations (see Figures 6 - 7). Mount the sensor on the mounting arm so that no shadow will be cast on it at any time of day, at any time of year, from obstructions such as trees, buildings or the mast or structure on which it is mounted.
SP-LITE Silicon Pyranometer SP-LITE 025STAND 019ALU Crossarm FIGURE 7. 025STAND and 019ALU Crossarm Mount the sensor on the mounting arm at a height of at least 1.5 m above the ground surface to minimize shading effects. PN 14282 mounting bracket has a built-in bubble level that is used to mount the SP-LITE to the 025STAND or 015ARM. Mount and adjust the SP-LITE as follows: 6 1. Attach the mounting arm to the tripod or tower at the required height. 2.
SP-LITE Silicon Pyranometer 4. Wiring The SP-LITE can be measured with a differential or single-ended channel on the datalogger; a differential channel is recommended. Radiation Signal White Signal Reference Green (User supplied jumper wire for differential measurement only) Shield Clear FIGURE 8. SP-LITE to Datalogger Connections TABLE 1.
SP-LITE Silicon Pyranometer 5.1 Datalogger Input Range Codes Normally the 15 mV range for the 21X and CR7, the 25 mV range for the CR10(X), CR500/CR510, and CR1000, and the 50 mV range for the CR23X are suitable. The parameter code for the input range also specifies the measurement integration time. The slow or 60 Hz rejection integration gives a more noisefree reading. A fast integration takes less power and allows for faster throughput.
SP-LITE Silicon Pyranometer EXAMPLE 1. Sample Instructions used to Measure an Average Flux with a CR10X ;{CR10X} ; *Table 1 Program 01: 10 Execution Interval (seconds) 01: Volt (Diff) (P2) 1: 1 Reps 2: 23** ± 25 mV 60 Hz Rejection Range 3: 1* DIFF Channel 4: 1* Loc [ W_m2 ] 5: 100*** Mult 6: 0 Offset ;Set negative values to zero.
SP-LITE Silicon Pyranometer 5.4 Program Example 2, Total Solar Radiation In Example 2 a daily total flux density is found. This total flux density is in MJ m-2 day-1. Negative values are set to zero before they are added to the running total. 5.4.1 Output Format Considerations If the solar radiation is totalized in units of kJ m-2, there is a possibility of overranging the output limits.
SP-LITE Silicon Pyranometer EXAMPLE 2. Sample Instructions used to Measure a Daily Total Flux Density with a CR10X ;{CR10X} ; *Table 1 Program 01: 10 Execution Interval (seconds) 01: Volt (SE) (P1) 1: 1 2: 23** 3: 1* 4: 1* 5: .001*** 6: 0 Offset Reps ± 25 mV 60 Hz Rejection Range SE Channel Loc [ MJ_m2 ] Mult ;Set negative values to zero.
SP-LITE Silicon Pyranometer 5.5 Program Example 3, Average and Total Solar Radiation Wiring for Example 3 Color White Green Jumpered to Clear Function Radiation Signal Signal Reference Example CR1000 Program Channels Used 1H 1L Shield EXAMPLE 3.
SP-LITE Silicon Pyranometer 6. Maintenance The SP-LITE is an ‘all weather’ instrument and is very stable, but should be handled with care. It requires little periodic maintenance, apart from cleaning the sensor surfaces carefully with a soft cloth using water or alcohol. 6.1 Calibration It is recommended that the SP-LITE is checked, and re-calibrated if necessary, every two years.
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