CNR4 Net Radiometer Revision: 9/13 C o p y r i g h t © 2 0 0 0 - 2 0 1 3 C a m p b e l l S c i e n t i f i c , I n c .
Warranty “PRODUCTS MANUFACTURED BY CAMPBELL SCIENTIFIC, INC. are warranted by Campbell Scientific, Inc. (“Campbell”) to be free from defects in materials and workmanship under normal use and service for twelve (12) months from date of shipment unless otherwise specified in the corresponding Campbell pricelist or product manual. Products not manufactured, but that are re-sold by Campbell, are warranted only to the limits extended by the original manufacturer.
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Table of Contents PDF viewers: These page numbers refer to the printed version of this document. Use the PDF reader bookmarks tab for links to specific sections. 1. Introduction .................................................................1 2. Cautionary Statements...............................................1 3. Initial Inspection .........................................................1 3.1 Ships With............................................................................................1 4.
Table of Contents 8. Troubleshooting........................................................30 8.1 8.2 8.3 8.4 Testing the Pyranometer.................................................................... 30 Testing the Pyrgeometer.................................................................... 31 Testing the Thermistor ...................................................................... 31 Testing the Pt-100 ............................................................................. 31 9.
Table of Contents B-2. B-3. B-4. B-5. B-6. B-7. Attaching the CNF4 to CNR4 using pan-head screws and washers .........................................................................................B-4 Making sure the cables are clear from the edges..............................B-5 CNF4 solar shield and four flat-head screws ...................................B-5 Attaching the solar shield to CNF4 using four flat-head screws ......B-6 Affixing the sensor label to CNF4 ......................................
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CNR4 Net Radiometer 1. Introduction The CNR4 is a research-grade net radiometer that measures the energy balance between incoming and outgoing radiation. Our dataloggers measure the CNR4’s output. This net radiometer offers a professional solution for scientific-grade energy balance studies. Before using the CNR4, please study: • • • 2. 3.
CNR4 Net Radiometer 4. Quickstart Please review Section 7, Operation, for wiring and CRBasic programming. Appendix B, CNF4 Heater/Ventilator, provides information about using the CNF4 heater/ventilator. 4.1 4.2 Siting Considerations 1. Mount the sensor so no shadow will be cast on it at any time of day from obstructions such as trees, buildings, or the mast or structure on which it is mounted.
CNR4 Net Radiometer 2. Attach the 26120 mounting bracket to the vertical mounting pipe, or CM200-series crossarm using the provided U-bolt (see FIGURE 4-2). FIGURE 4-2. Attaching the CNR4 onto the mounting rod (pn 26120) using vertical pole or horizontal crossarm 3. CAUTION Insert the sensor’s support arm into the mounting block of the mounting bracket kit. Make sure the sensor points in the direction of the arrows that appear after the word SENSOR on top of the bracket (see FIGURE 4-2).
CNR4 Net Radiometer 4.3 6. Perform the fine leveling using the two spring-loaded leveling screws— one on the front and the other on the back of the bracket. 7. Route the sensor cable to the instrument enclosure. 8. Use the UV-resistant cable ties included with the tripod or tower to secure the cable to the vertical pipe or crossarm and tripod/tower.
CNR4 Net Radiometer 2. Select the datalogger and enter the scan interval. 3. Select CNR4 Net Radiometer, and select the right arrow (in center of screen) to add it to the list of sensors to be measured, and then select Next.
CNR4 Net Radiometer 6 4. Enter the sensitivity values supplied on the manufacturer’s certificate of calibration; these sensitivity values are unique to each sensor. The public variables defaults can typically be used. After entering the information, click on OK, and then select Next. 5. Choose the outputs and then select Finish. 6. In the Save As window, enter an appropriate file name and select Save.
CNR4 Net Radiometer 5. 7. In the Confirm window, click Yes to download the program to the datalogger. 8. Click on Wiring Diagram and wire according to the wiring diagram generated by Short Cut. Overview The CNR4 Net Radiometer consists of a pyranometer pair, one facing upward, the other facing downward, and a pyrgeometer pair in a similar configuration. The pyranometer pair measures short-wave solar radiation, and the pyrgeometer pair measures long-wave far infrared radiation.
CNR4 Net Radiometer and is resistant to a variety of pollutants and UV-radiation. The mounting rod can be unscrewed for transport. An optional ventilation unit with a heater, CNF4, is designed as an extension of the solar shield and can be fitted to the CNR4 or retrofitted later. The heater/ventilation unit is compact and provides efficient air-flow over the domes and windows to minimize the formation of dew and to reduce the frequency of cleaning. The integrated heater can be used to melt frost.
CNR4 Net Radiometer The properties of the CNR4 are mainly determined by the properties of the individual probes. Generally the accuracy of the CNR4 will be higher than that of competitive net-radiometers, because the solar radiation measurement performed by the pyranometer is accurate, and offers a traceable calibration. Also the optionally integrated heater/ventilator unit improves the accuracy.
CNR4 Net Radiometer 6.1 CNR4 Specifications Sensor sensitivities: Four probes with unique sensitivity values. Please refer to the calibration sheets or label on the bottom of the sensor for the sensitivity values. Operating temperature: –40 to +80°C (–40 to 176°F) Operating humidity: 0 to 100% RH Bubble level sensitivity: < 0.
CNR4 Net Radiometer Directional error*: Zero offset due to 0 to -200 W/m2 IR net irradiance*: Zero offset due to temperature change*: Operating temperature: < 20 W/m2 at angle up to 80° with 1000 W/m2 < 15 W/m2 < 3 W/m2 (5 K/hr temperature change) < 1 W/m2 (with CNF4 installed) –40°C to +80°C Field of view 6.
CNR4 Net Radiometer Field of view Upper: 180 degrees Lower: 150 degrees Net-irradiance: –250 to +250 W/m2 Non-stability: < 1% (sensitivity change per year) Window heating offset: < 6 W/m2 (1000 W/m2 solar irradiance) Uncertainty in daily total: < 10% (95% confidence level) indoor calibration Typical signal output for atmospheric application: ±5 mV Temperature sensors Thermistor: 10k Ω Pt-100: DIN class A Instrument calibration: 6.
CNR4 Net Radiometer 7. Operation 7.1 Using the CNR4 in the Four Separate Components Mode In the four separate components mode configuration (measuring two shortwave radiation signals and two long-wave signals), all signals are measured separately. Calculation of net-radiation and albedo can be done online by the datalogger, or offline by the user during post-processing, using the stored raw data. The two pyranometers will measure the short-wave radiation, both incoming and reflected.
CNR4 Net Radiometer For the pyrgeometer only E = V/C + 5.67•10-8•T4 (7-2) In this equation, C is the sensitivity of the sensor. T is in Kelvin, and not in Celsius or Fahrenheit. NOTE The downward-facing pyrgeometer measures the far infrared radiation that is emitted by the ground. The upward-facing pyrgeometer measures the far infrared radiation from the sky. As the sky is typically colder than the instrument, one can expect negative voltage signals from the upward-facing pyrgeometer.
CNR4 Net Radiometer TABLE 7-1. Resistance values versus CNR4’s thermistor temperature in °C.
CNR4 Net Radiometer TABLE 7–2. Resistance values versus CNR4’s Pt–100 temperature in °C. Temperature [°C] –30 –29 –28 –27 –26 –25 –24 –23 –22 –21 –20 –19 –18 –17 –16 –15 –14 –13 –12 –11 –10 –9 –8 –7 –6 –5 –4 –3 –2 –1 Resistance [Ω] 88.22 88.62 89.01 89.40 89.80 90.19 90.59 90.98 91.37 91.77 92.16 92.55 92.95 93.34 93.73 94.12 94.52 94.91 95.30 95.69 96.09 96.48 96.87 97.26 97.65 98.04 98.44 98.83 99.22 99.
CNR4 Net Radiometer Albedo will always be smaller than 1. Checking this can be used as a tool for quality assurance of your data. If you know the approximate albedo at your site, the calculation of albedo can also serve as a tool for quality control of your measured data at a specific site. 7.1.5 Calculation of Net Short-wave Radiation The net short-wave solar radiation is equal to the incoming (downwelling) short-wave radiation minus the reflected (upwelling) short-wave radiation.
CNR4 Net Radiometer 7.1.7 Calculation of Net (Total) Radiation In the four separate components mode, net radiation, Rn, can be calculated using the individual sensor measurement results: Rn = {(E upper Pyranometer) - (E lower Pyranometer)} + {(E upper Pyrgeometer) - (E lower Pyrgeometer)} (7-8) Where E upper/lower pyranometers are calculated according to Equation 7-1, and E upper/lower pyrgeometers are calculated according to Equation 7-2. The terms with T cancel each other out. 7.
CNR4 Net Radiometer FIGURE 7-2. The marks on the end of the CNR4: S for SOLAR cable, and T for TEMP cable The measurement details for Pt-100 sensor, including the wiring diagram and sample program, are explained in Appendix C, CR3000 Program for Measuring Pt-100 Temperature Sensor. The four radiation outputs can be measured using differential or single-ended inputs on the datalogger. A differential voltage measurement is recommended because it has better noise rejection than a single-ended measurement.
CNR4 Net Radiometer FIGURE 7-4. Labels on the pigtail end of the TEMP cable. TABLE 7-3.
CNR4 Net Radiometer 7.3 Datalogger Programming The CNR4 outputs four voltages that typically range from 0 to 15 mV for the pyranometers, and ± 5 mV for the pyrgeometers. A differential voltage measurement is recommended because it has better noise rejection than a single-ended measurement. If differential channels are not available, singleended measurements can be used.
CNR4 Net Radiometer Average short-wave net radiation Average long-wave net radiation Average albedo Average net radiation 'CR1000 Series Datalogger ' 'CNR4 program 'This program measures CNR4 four-component net radiometer 'This program also measures the thermistor inside the CNR4 ' 'User must enter the sensitivity values for all four probes in the program and save/compile 'prior to downloading it to the datalogger. 'Search for the text string "unique" to find places to enter the sensitivity values.
CNR4 Net Radiometer Units Units Units Units Units Units Units Units Units Units Units Units Units Units logger_temp = degC batt_volt = volts short_up = W/m^2 short_dn = W/m^2 long_up = W/m^2 long_dn = W/m^2 cnr4_T_C = deg_C cnr4_T_K = K long_up_corr = W/m^2 long_dn_corr = W/m^2 Rs_net = W/m^2 Rl_net = W/m^2 albedo = W/m^2 Rn = W/m^2 Dim Rs, Vs_Vx 'CNR4 sensitivities: refer to the Certificate of Calibration from Kipp & Zonen 'for each probes, and enter them below. Const pyranometer_up_sensitivity = 15.
CNR4 Net Radiometer Scan (1,Sec,3,0) PanelTemp (logger_temp,250) Battery (batt_volt) 'CNR4 radiation measurements VoltDiff (cnr4(),4,mV20C,1,True ,0,_60Hz,cnr4_mult(),0) 'CNR4 thermistor measurement BrHalf (Vs_Vx,1,mV2500,16,Vx2,1,2500,True ,0,250,1.0,0) Rs = 1000*(Vs_Vx/(1-Vs_Vx)) cnr4_T_C = 1/(1.0295e-3+2.391e-4*LN(Rs)+1.568e-7*(LN(Rs))^3)-273.15 'Convert CNR4 temperature to Kelvin cnr4_T_K = cnr4_T_C+273.15 'Correct the long-wave radiation values from pyrgeometers long_up_corr = long_up+5.
CNR4 Net Radiometer 'CR3000 Series Datalogger ' 'CNR4 program 'This program measures CNR4 four-component net radiometer 'This program also measures the thermistor inside the CNR4 ' 'User must enter the sensitivity values for all four probes in the program and save/compile 'prior to downloading it to the datalogger. 'Search for the text string "unique" to find places to enter the sensitivity values.
CNR4 Net Radiometer Units Units Units Units Units Units long_up_corr = W/m^2 long_dn_corr = W/m^2 Rs_net = W/m^2 Rl_net = W/m^2 albedo = W/m^2 Rn = W/m^2 Dim Rs, Vs_Vx 'CNR4 sensitivities: refer to the Certificate of Calibration from Kipp & Zonen 'for each probes, and enter them below. Const pyranometer_up_sensitivity = 15.35 'unique sensitivity '(microV/W/m^2) Const pyranometer_dn_sensitivity = 15.41 'unique sensitivity '(microV/W/m^2) Const pyrgeometer_up_sensitivity = 8.
CNR4 Net Radiometer 'CNR4 thermistor measurement BrHalf (Vs_Vx,1,mv5000,16,Vx1,1,2500,True ,0,250,1.0,0) Rs = 1000*(Vs_Vx/(1-Vs_Vx)) cnr4_T_C = 1/(1.0295e-3+2.391e-4*LN(Rs)+1.568e-7*(LN(Rs))^3)-273.15 'Convert CNR4 temperature to Kelvin cnr4_T_K = cnr4_T_C+273.15 'Correct the long-wave radiation values from pyrgeometers long_up_corr = long_up+5.67e-8*cnr4_T_K^4 long_dn_corr = long_dn+5.
CNR4 Net Radiometer 'CR5000 Series Datalogger ' 'CNR4 program 'This program measures CNR4 four-component net radiometer 'This program also measures the thermistor inside the CNR4 ' 'User must enter the sensitivity values for all four probes in the program and save/compile 'prior to downloading it to the datalogger. 'Search for the text string "unique" to find places to enter the sensitivity values.
CNR4 Net Radiometer Units Units Units Units Units Units Units cnr4_T_K = K long_up_corr = W/m^2 long_dn_corr = W/m^2 Rs_net = W/m^2 Rl_net = W/m^2 albedo = W/m^2 Rn = W/m^2 Dim Rs, Vs_Vx 'CNR4 sensitivities: refer to the Certificate of Calibration from Kipp & Zonen for sensitivity values 'for each probes, and enter them below. Const pyra_up_sensitiv = 15.35 'unique sensitivity for upper pyranometer (microV/W/m^2) Const pyra_dn_sensitiv = 15.
CNR4 Net Radiometer 'Convert CNR4 temperature to Kelvin cnr4_T_K = cnr4_T_C+273.15 'Correct the long-wave radiation values from pyrgeometers long_up_corr = long_up+5.67e-8*cnr4_T_K^4 long_dn_corr = long_dn+5.67e-8*cnr4_T_K^4 'Compute short-wave net radiation Rs_net = short_up - short_dn 'Compute long-wave net radiation Rl_net = long_up - long_dn 'Compute albedo albedo = short_dn/short_up 'Compute net radiation Rn = Rs_net + Rl_net CallTable cnr4_dat CallTable cnr4_ts NextScan EndProg 8.
CNR4 Net Radiometer voltmeter to its most sensitive range setting. Darken the sensor. The signal should read zero; this response can take up to one minute. Small deviations from zero are possible; this is caused by the thermal effects, such as touching the pyranometer with your hand. This thermal effect can be demonstrated by deliberately heating the pyranometer with your hand. If the zero offset is within specifications, proceed with the third test. In the third test, the sensor should be exposed to light.
CNR4 Net Radiometer 9. Maintenance and Recalibration The CNR4 is weatherproof, and is intended for a continuous outdoor use. The materials used in the pyranometer and the pyrgeometer are robust and require little maintenance. For optimal results, however, proper care must be taken. 9.1 Cleaning Windows and Domes The radiometer readings can be reduced if domes and windows are not clean. The site operator should check the windows and domes of the CNR4 regularly, and clean them as needed.
CNR4 Net Radiometer Drying Cartridge Rubber Gasket FIGURE 9-1. Replacing the drying cartridge 9.4 Replacement Parts The following is the list of replacement parts for the CNR4 and CNF4 (heater/ventilator) available from Campbell Scientific. CSI Part Number Description CNR4CBL1-L Replacement CNR4 Solar Cable CNR4CBL2-L Replacement CNR4 Temperature Cable CNF4CBL-L Replacement CNF4 Cable 26006 Replacement Drying Cartridges 26010 Replacement Fan Filter (Set of 5).
CNR4 Net Radiometer 34
Appendix A. CNR4 Performance and Measurements under Different Conditions TABLE A-1 shows 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 shows 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.
Appendix A. CNR4 Performance and Measurements under Different Conditions Upwelling signal Signal(downward (Downwardfacing) Facing) Pyrgeometer upwelling pyrgeometer 30 Pyrgeometer: U‐emf / sensitivity [W/m²] Temp of instrument [°C] 20 10 0 ‐10 ‐20 ‐30 0:00:00 23:00:00 22:00:00 21:00:00 20:00:00 19:00:00 18:00:00 17:00:00 16:00:00 15:00:00 14:00:00 13:00:00 12:00:00 11:00:00 10:00:00 9:00:00 8:00:00 7:00:00 6:00:00 5:00:00 4:00:00 3:00:00 2:00:00 1:00:00 0:00:00 FIGURE A-3.
Appendix A. CNR4 Performance and Measurements under Different Conditions ⎡ E upper CG3 ⎤ Sky Temperature = ⎢ ⎥ ⎣ 5.67 ⋅10 −8 ⎦ 1/ 4 ⎡ E lower CG3 ⎤ Ground Temperatur e = ⎢ ⎥ ⎣ 5.
Appendix B. CNF4 Heater/Ventilator NOTE Whenever the heater is used, the heating may cause errors in the measurement of the sensor temperature. Under most conditions, the accuracy gained by heating will be larger than the errors introduced by heating. In both the pyranometer and the pyrgeometer, thermal sensors are used, and these sensors, in principle, measure a heat flow. For optimal performance, these sensors should be at thermal equilibrium with the ambient air.
Appendix B. CNF4 Heater/Ventilator Not available 10 watt power available? DO NOT HEAT Available Consider op options tions below Not Available DO NOT HEAT (recommendation) Clock and relay available? Available Heat from 1 hour before sunset until 1 hour after sunrise. The heater power can be controlled using one of the SW12V channels of the Campbell Scientific dataloggers. The heater’s current drain is approximately 850 mA at 12 Vdc (10 watts).
Appendix B. CNF4 Heater/Ventilator B.2 Attaching the Optional CNF4 Heater/Ventilator Unit to CNR4 1. The CNF4 heater/ventilator unit comes with the following: the heater/ventilator, the white solar shield, three pan-head screws with washers, and four flat-head screws as shown in FIGURE B-1. FIGURE B-1.
Appendix B. CNF4 Heater/Ventilator 2. Attach the heater/ventilator unit unto the bottom of the CNR4 sensor, using the three pan-head screws and washers, as shown in FIGURE B-2. Make sure that the pyranometer and the pyrgeometer windows are not scratched during the installation. FIGURE B-2.
Appendix B. CNF4 Heater/Ventilator 3. Make sure the cables are cleared from the edges of the CNF4, as shown in FIGURE B-3, and place the white solar shield over it. Use the four flathead screws provided to complete the solar shield installation to the CNF4, as shown in FIGURE B-4 and FIGURE B-5. FIGURE B-3. Making sure the cables are clear from the edges FIGURE B-4.
Appendix B. CNF4 Heater/Ventilator FIGURE B-5. Attaching the solar shield to CNF4 using four flat-head screws 4. Once the CNF4 heater/ventilator unit is attached to the bottom side of the CNR4, the CNF4 will cover the label that contains the serial number and the sensitivity values for the four sensors. Affix the extra label that came with the sensor to the bottom side of the CNF4’s anodized aluminium base so that the label is in a visible location. See FIGURE B-6 below. FIGURE B-6.
Appendix B. CNF4 Heater/Ventilator B.3 Wiring The following table shows the recommended datalogger wiring for using the CNR4 sensor with the CNF4 heater/ventilator while making the differential measurement. TABLE B-1.
Appendix B. CNF4 Heater/Ventilator B.4 Example B, CR3000 Datalogger Program with Heater/Ventilator Control Example B measures the four radiation outputs, thermistor temperature, and controls the ventilator and heater using SW12V-1 and SW12V-2 channels on the CR3000, respectively. In this example program, the ventilator and heater can be turned on or off by manually setting the flag(1) and flag(2) high or low, respectively.
Appendix B.
Appendix B.
Appendix B. CNF4 Heater/Ventilator 'Compute net radiation Rn = Rs_net + Rl_net 'CNF4 ventilator control - the ventilator will be turned on when flag(1) is set high SW12 (1,flag(1)) 'CNF4 heater control - the heater will be turned on when flag(2) is set high SW12 (2,flag(2)) CallTable cnr4_data CallTable cnr4_ts NextScan EndProg B.5 CNF4 Heater/Ventilator Maintenance B.5.1 Testing the Heater The optional CNF4 consists of a heater and a ventilator.
Appendix B.
Appendix C. CR3000 Program for Measuring Pt-100 Temperature Sensor Example C measures the Pt-100 sensor for the body temperature of the CNR4. This program requires four differential channels to measure the four radiation outputs, one current excitation channel, and one differential channel for Pt-100 measurement. The program measures the sensors every 1 second, performs the online processing of the data, and stores the following processed data to a data table called cnr4_data once every 60 minutes.
Appendix C. CR3000 Program for Measuring Pt-100 Temperature Sensor 'CR3000 Series Datalogger ' 'CNR4 program 'This program measures CNR4 four-component net radiometer 'This program also measures the Pt-100 sensor inside the CNR4 ' 'User must enter the sensitivity values for all four probes in the program and save/compile 'prior to downloading it to the datalogger. 'Search for the text string "unique" to find places to enter the sensitivity values.
Appendix C. CR3000 Program for Measuring Pt-100 Temperature Sensor Units Units Units Units Units Units Units cnr4_T_K = K long_up_corr = W/m^2 long_dn_corr = W/m^2 Rs_net = W/m^2 Rl_net = W/m^2 albedo = W/m^2 Rn = W/m^2 Dim cnr4_prt_R, Rs_R0 'CNR4 sensitivities: refer to the Certificate of Calibration from Kipp & Zonen 'for each probes, and enter them below. Const pyranometer_up_sensitivity = 15.35 'unique sensitivity '(microV/W/m^2) Const pyranometer_dn_sensitivity = 15.
Appendix C. CR3000 Program for Measuring Pt-100 Temperature Sensor 'PRT (Pt-100) temperature measurement Resistance (cnr4_prt_R,1,mV200,8,Ix1,1,1500,True,True,0,_60Hz,1,0) Rs_R0 = cnr4_prt_R/100 PRT (cnr4_T_C,1,Rs_R0,1,0) 'Convert CNR4 temperature to Kelvin cnr4_T_K = cnr4_T_C+273.15 'Correct the long-wave radiation values from pyrgeometers long_up_corr = long_up+5.67e-8*cnr4_T_K^4 long_dn_corr = long_dn+5.
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