CNR1 Net Radiometer Revision: 1/08 C o p y r i g h t © 2 0 0 0 - 2 0 0 8 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 CNR1 NET RADIOMETER 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.
CNR1 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 2. Sensor Specifications .................................................1 2.1 CNR1 Specifications ................................................................................1 2.2 CM3 Specifications .....................................................
CNR1 Table of Contents Figures 2-1. 3-1. 5-1. 5-2. 6-1. The Dimensions of the CNR1................................................................. 2 CNR1 Mounting Options........................................................................ 4 CNR1 Schematic. ................................................................................... 8 Interfacing the Pt-100 Using the 4WPB100 Module.............................. 9 4WPB100 Module ...................................................................
CNR1 Net Radiometer 1. General Description The CNR1 Net Radiometer is intended for the analysis of the radiation balance of Solar and Far Infrared radiation. The most common application is the measurement of Net (total) Radiation at the earth's surface. The CNR1 design is such that both the upward-facing and the downwardfacing instruments measure the energy that is received from the whole hemisphere (180 degrees field of view). The output is expressed in Watts per square meter.
CNR1 Net Radiometer Cable length: Weight: Mounting arm attached to CNR1: 15 m (each cable) 4 kg 14.5” (37 cm) long 5/8” (1.6 cm) diameter FIGURE 2-1. The Dimensions of the CNR1 2.2 CM3 Specifications Specifications that are part of the ISO classification: 2 Response time 95%: 18 s Non-stability: < 1% change per year Non-linearity: Max. dev. 2.5% (0-1000 W m-2) Directional error: Max. 25 W m-2 at 1000 W m-2 Spectral selectivity: Max. dev.
CNR1 Net Radiometer Tilt response: Max. dev. 2% Overall ISO classification: second class Sensitivity: 10 - 35 µV/(W m-2) Impedance: 125 Ohm nominal Operating temperature: -40°C to +80°C Spectral range: 305-2800 nm (50% points) Expected signal range for atmospheric application: 0 - 15 mV typical Expected accuracy for daily sums: ± 10% Window heating offset: Max. 25 W m-2 at 1000 W m-2 normal incidence solar radiation 2.
CNR1 Net Radiometer Northern Hemisphere this implies that the Net Radiometer should be mounted south of the mast. It is suggested that the CNR1 is mounted at a height of at least 1.5 meters above the surface to avoid shading effects of the instruments on the soil and to promote spatial averaging of the measurement. If the instrument is H meters above the surface, 99% of the input of the lower sensors comes from a circular area with a radius of 10 H. Shadows or surface disturbances with radius < 0.
CNR1 Net Radiometer 4. Using the CNR1 in the Four Separate Components Mode (4SCM) In the 4SCM configuration (measuring two Solar Radiation signals, two Far Infrared signals and, for calculation purposes, one Pt-100 signal), all signals are measured separately. Calculation of Net-Radiation and albedo can be done by the datalogger, or later by the computer from the radiation and temperature data. The two CM3s will measure the solar radiation, both incoming and reflected.
CNR1 Net Radiometer For the CG3 only E = V/C + 5.67 ⋅ 10-8 ∗ T4 (4.2) In this equation C is the sensitivity of the sensor. Please bear in mind that T is in Kelvin, and not in Celsius or Fahrenheit. 4.3 Measuring the CNR1’s Temperature with the Pt-100 The Pt-100 temperature sensor is located in the CNR1 body. It will not measure the exact temperature of the CG3 unless the whole instrument is in thermal equilibrium.
CNR1 Net Radiometer Net Solar radiation = (E upper CM3) - (E lower CM3) (4.4) In this formula E is calculated according to Equation 4.1. Net Solar radiation will always be positive. Checking this can be used as a tool for quality assurance of your measured data. 4.6 Calculation of the Net Infrared Radiation (Net Long-Wave) Net Far Infrared radiation is, like Net Solar radiation, the part that contributes to heating or cooling of the earth's surface.
CNR1 Net Radiometer show wiring for both CNR1 and 4WPB100 modules. Wiring diagrams and Tables 5-1 and 5-2 are applicable only if you bought the CNR1 Net Radiometer from Campbell Scientific, Inc. Use of the CNR1 Net Radiometer, which you bought outside of Campbell Scientific, is possible only on the CR3000 and CR5000 dataloggers. The PT-100 can connect directly to the CR3000 and CR5000 because they have current excitation inputs. Table 5-3 and Program Example 6.2.
CNR1 Net Radiometer DATALOGGER EX1 4WPB100 10K 5H H 100 CNR1 5L L Red G 6H Yellow PT-100 6L Green Blue FIGURE 5-2. Interfacing the Pt-100 Using the 4WPB100 Module The four radiation outputs can be measured using Differential or Single-Ended inputs on the datalogger. A differential voltage measurement (Instruction 2) is recommended because it has better noise rejection than a single-ended measurement.
CNR1 Net Radiometer Pt-100 Temperature Sensor Connections to 4WPB100 and Datalogger Function Color Black Pt-100 Excitation + Pt-100 Excitation Pt-100 Signal + Pt-100 Signal – Red Blue Yellow Green 4WPB100 Wire H L G Datalogger Excitation Differential Input (H) Differential Input (L) (AG CR10X/CR510) Differential Input (H) Differential Input (L) TABLE 5-2.
CNR1 Net Radiometer comparing the results of single-ended and differential measurements made under the same conditions. For the CR3000 and CR5000, one differential channel and a current excitation channel are required to measure the PT-100. For the other dataloggers, two differential channels and the 4WPB100 module are required to measure the Pt-100 temperature sensor. NOTE The 4WPB100 is included with the CNR1 sensor purchased from CSI. FIGURE 6-1. 4WPB100 Module 6.
CNR1 Net Radiometer Array ID Year Julian Day Hour/Minute Avg CM3 Up (shortwave radiation) Avg CM3 Down (shortwave radiation) Avg CG3 Up (longwave radiation) Avg CG3 Down (longwave radiation) Avg CNR1 temperature (degrees C) Avg CNR1 temperature (degrees K) Avg Net shortwave radiation Avg Net longwave radiation Avg Albedo Avg Total Net radiation Avg temperature corrected CG3 Up Avg temperature corrected CG3 Down Wiring for Program Example 1 Color Red Blue White Black Grey or Orange Yellow Brown Green Shield
CNR1 Net Radiometer ;{CR23X} ;Program Example 1 for CR23X datalogger ; ;CNR1 sensitivity for program example = 7.30 uV/W/m^2 ;Multiplier for measurement instructions = 1000/7.30 = 136.99 ; ;*Table 1 Program 01: 2 Execution Interval (seconds) ;Measure CM3 Up and CM3 Down (shortwave radiation) ;Note: Multiplier (Parameter 5) will be different for each CNR1 1: Volt (Diff) (P2) 1: 2 2: 22+ 3: 1* 4: 1* 5: 136.
CNR1 Net Radiometer ;Net CM3 shortwave radiation = CM3 Up - CM3 Down 6: Z=X-Y (P35) 1: 1 2: 2 3: 7 X Loc [ CM3_up ] Y Loc [ CM3_dn ] Z Loc [ Net_Rs ] ;Net CG3 longwave radiation = CG3 Up - CG3 Down 7: Z=X-Y (P35) 1: 3 2: 4 3: 8 X Loc [ CG3_up ] Y Loc [ CG3_dn ] Z Loc [ Net_Rl ] ;Albedo = CM3 Down / CM3 Up 8: Z=X/Y (P38) 1: 2 2: 1 3: 9 X Loc [ CM3_dn ] Y Loc [ CM3_up ] Z Loc [ Albedo ] ;Net total radiation = (CM3 Up + CG3 Up) - (CM3 Down + CG3 Down) 9: Z=X+Y (P33) 1: 1 2: 3 3: 23 X Loc [ CM3_up ] Y L
CNR1 Net Radiometer 15: Z=X*Y (P36) 1: 25 X Loc [ scratch_1 ] 2: 27 Y Loc [ scratch_3 ] 3: 28 Z Loc [ scratch_4 ] 16: Z=X+Y (P33) 1: 3 X Loc [ CG3_up ] 2: 28 Y Loc [ scratch_4 ] 3: 11 Z Loc [ CG3_upCor ] 17: Z=X+Y (P33) 1: 4 X Loc [ CG3_dn ] 2: 28 Y Loc [ scratch_4 ] 3: 12 Z Loc [ CG3_dnCor ] ; ;Output data to final storage every 60 minutes 18: If time is (P92) 1: 0 Minutes (Seconds --) into a 2: 60 Interval (same units as above) 3: 10 Set Output Flag High (Flag 0) 19: Real Time (P77) 1: 0220 Day,Hour/Minu
CNR1 Net Radiometer Wiring for Program Example 2 Color Function Red Blue White Black Grey or Orange Yellow Brown Green Shield CM3 Up Signal CM3 Up Reference CM3 Down Signal CM3 Down Reference CG3 Up Signal CG3 Up Reference CG3 Down Signal CG3 Down Reference Shield Example CR23X Program Channels Used SE1 SE2 SE3 SE4 Pt-100 Temperature Sensor Connections to 4WPB100 and Datalogger Color Function Red Blue Yellow Green Pt-100 Excitation + Pt-100 Excitation Pt-100 Signal + Pt-100 Signal - 4WPB100 H L G
CNR1 Net Radiometer ;Measure CNR1 temperature 3: Full Bridge w/mv Excit (P9) 1: 1 Reps 2: 22 50 mV, 60 Hz Reject, Slow, Ex Range 3: 22 50 mV, 60 Hz Reject, Slow, Br Range 4: 5 DIFF Channel 5: 1 Excite all reps w/Exchan 1 6: 4200 mV Excitation 7: 5 Loc [ Temp_C ] 8: 1 Mult 9: 0 Offset 4: Temperature RTD (P16) 1: 1 Reps 2: 5 R/R0 Loc [ Temp_C 3: 5 Loc [ Temp_C ] 4: 1.0 Mult 5: 0 Offset 5: Z=X+F (P34) 1: 5 2: 273.
CNR1 Net Radiometer Year Julian Day Hour/Minute Avg CM3 Up (shortwave radiation) Avg CM3 Down (shortwave radiation) Avg CG3 Up (longwave radiation) Avg CG3 Down (longwave radiation) Avg CNR1 temperature (degrees C) Avg CNR1 temperature (degrees K) Avg Net shortwave radiation Avg Net longwave radiation Avg Albedo Avg Total Net radiation Avg temperature corrected CG3 Up Avg temperature corrected CG3 Down 'CR1000 'Declare Variables and Units Public Batt_Volt Public CM3Up Public CM3Dn Public CG3Up Public CG3Dn
CNR1 Net Radiometer 'Define Data Tables DataTable(Table1,True,-1) DataInterval(0,60,Min,10) Average(1,CM3Up,FP2,False) Average(1,CM3Dn,FP2,False) Average(1,CG3Up,FP2,False) Average(1,CG3Dn,FP2,False) Average(1,CNR1TC,FP2,False) Average(1,CNR1TK,FP2,False) Average(1,NetRs,FP2,False) Average(1,NetRl,FP2,False) Average(1,Albedo,FP2,False) Average(1,UpTot,FP2,False) Average(1,DnTot,FP2,False) Average(1,NetTot,FP2,False) Average(1,CG3UpCo,FP2,False) Average(1,CG3DnCo,FP2,False) EndTable 'Main Program BeginProg
CNR1 Net Radiometer Year Julian Day Hour/Minute Avg CM3 Up (shortwave radiation) Avg CM3 Down (shortwave radiation) Avg CG3 Up (longwave radiation) Avg CG3 Down (longwave radiation) Avg CNR1 temperature (degrees C) Avg CNR1 temperature (degrees K) Avg Net shortwave radiation Avg Net longwave radiation Avg Albedo Avg Total Net radiation Avg temperature corrected CG3 Up Avg temperature corrected CG3 Down 'CR5000 Series Datalogger 'ANALOG INPUT '1H CM3 UP - downwelling shortwave radiation signal (red) '1L CM3
CNR1 Net Radiometer Units Batt_Volt=Volts Units CM3Up=W/meter² Units CM3Dn=W/meter² Units CG3Up=W/meter² Units CG3Dn=W/meter² Units CNR1TC=Deg C Units CNR1TK=K Units NetRs=W/meter² Units NetRl=W/meter² Units Albedo=W/meter² Units UpTot=W/meter² Units DnTot=W/meter² Units NetTot=W/meter² Units CG3UpCo=W/meter² Units CG3DnCo=W/meter² 'Define Data Tables DataTable(Table1,True,-1) DataInterval(0,60,Min,10) Average(1,CM3Up,FP2,False) Average(1,CM3Dn,FP2,False) Average(1,CG3Up,FP2,False) Average(1,CG3Dn,FP2,Fals
CNR1 Net Radiometer EndProg Albedo=CM3Dn/CM3Up UpTot=CM3Up+CG3Up DnTot=CM3Dn+CG3Dn NetTot=UpTot-DnTot CG3UpCo=CG3Up+5.67*10^-8*CNR1TK^4 CG3DnCo=CG3Dn+5.67*10^-8*CNR1TK^4 'Call Data Tables and Store Data CallTable(Table1) NextScan 7. Calibration The CNR1 should be recalibrated every two years, or as an alternative, by letting a higher standard run parallel to it over a two-day period and then comparing the results. For comparison of pyranometers, one should use a clear day.
CNR1 Net Radiometer zero. Bear in mind that the response takes about one minute. Small deviations from zero are possible; this is caused by thermal effects like touching the pyranometer with your hand. The latter effect can be demonstrated by deliberately heating the CM3 with your hand. Another cause might be the zero offset of the amplifier. When this is the case, the same offset will also be present when the amplifier is short-circuited with a 200 Ohm resistor. This is an amplifier error.
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Appendix A. CNR1 Performance and Measurements under Different Conditions Below, Table A-1, shows an indication of what one might typically expect to measure under different meteorological conditions. The first parameter is day and night. At night, the Solar radiation is zero. The second column indicates if it is cloudy or clear. A cloud acts like a blanket, absorbing part of the Solar radiation, and keeping Net Far Infrared radiation close to zero. The third parameter is ambient temperature.
Appendix A. CNR1 Performance and Measurements under Different Conditions TABLE A-1. Typical output signals of CNR1 under different meteorological conditions. Explanation can be found in the text.
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