NR01 Four-Component Net Radiation Sensor Revision: 8/11 C o p y r i g h t © 2 0 0 8 - 2 0 1 1 C a m p b e l l S c i e n t i f i c , I n c .
Warranty and Assistance 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 on the corresponding Campbell invoice. Batteries, fine-wire thermocouples, desiccant, and other consumables have no warranty.
NR01 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. Introduction..................................................................1 2. Measurement Principle ...............................................3 2.1 2.2 2.3 2.4 2.5 2.6 2.7 General......................................................................................................3 NR01 Construction ....................
NR01 Table of Contents Figures 1-1. Atmospheric Radiation as a Function of Wavelength ............................ 2 2.2-1. The NR01 Four-Component Net Radiation Sensor............................. 4 2.3-1. Spectral Response of the Pyranometer Compared to the Solar Spectrum .......................................................................................... 5 2.4-1. Spectral Response of the Pyrgeometer Compared to the Atmospheric LW Spectrum............................................................
NR01 Four-Component Net Radiation Sensor The NR01 is a four-component net radiation sensor that is used for scientific-grade energy balance studies. 1. Introduction The NR01 has separate measurements of solar (Short Wave or SW) and Far Infra-Red (Long Wave or LW) radiation. It offers a professional solution to the measurement of net radiation and its four main components. The NR01 is robust and requires only limited maintenance.
NR01 Four-Component Net Radiation Sensor FIGURE 1-1. Atmospheric Radiation as a Function of Wavelength LW or FIR radiation is mainly present in the 4500 to 50000 nm region, while SW or solar radiation is mainly present in the 300 to 3000 nm region. The two are measured separately. Major improvements of the NR01 relative to comparable instruments include reduced weight, reduced solar offsets in the LW signal, ease of leveling (because a 2-axis leveling assembly is built-in).
NR01 Four-Component Net Radiation Sensor The NR01 is supplied with four separate instrument sensitivities. As a brief explanation, to calculate the radiation level, the sensor output voltage, U, must be divided by the sensor sensitivity; a constant, E, that is supplied with each individual instrument. For example: Φ = SWin = Upyrano, up / Epyrano, up More information can be found in the chapter on instrument performance. WARNING The NR01 is a passive sensor, and does not need any power.
NR01 Four-Component Net Radiation Sensor NOTE The following equations assume the temperature is in Kelvin. Add 273.15 to equations 2.1-9 and 2.1-10 for temperature in degree Celsius. Tsurface = (LWout /5.67.10-8)1/4 Tsky = (LWin /5.67.10-8)1/4 2.1-9 2.1-10 2.2 NR01 Construction FIGURE 2.2-1.
NR01 Four-Component Net Radiation Sensor 2.3 Pyranometers A pyranometer should measure the solar or SW radiation flux from a field of view of 180 degrees. The atmospheric SW radiation spectrum extends roughly from 300 to 2800 nm. It follows that a pyranometer should cover that spectrum with a spectral sensitivity that is as “flat” as possible. For a flux measurement, it is required by definition that the response to “beam” radiation varies with the cosine of the angle of incidence.
NR01 Four-Component Net Radiation Sensor The black coating on the thermopile sensor absorbs the solar radiation. This radiation is converted to heat. The heat flows through the sensor to the pyranometer housing. The thermopile sensor generates a voltage output signal that is proportional to the solar radiation. SWin = Upyrano, up / Epyrano, up 2.3-1 In case of the NR01, the pyranometer is type SR01. This is a second-class pyranometer according to the WMO and ISO classification system (ISO 9060).
NR01 Four-Component Net Radiation Sensor To attain the proper directional and spectral characteristics, a pyrgeometer’s main components are: 1 Thermopile sensor with a black coating—absorbs all LW and SW radiation, provides a flat spectrum covering the 300 to 50000 nanometer range, and has a near-perfect cosine response.
NR01 Four-Component Net Radiation Sensor coefficient of 1). For example, equation 2.4-2 calculates, in Kelvin, the sky temperature: Tsky = (LWin /5.67.10-8)1/4 2.4-2 The NR01’s pyrgeometers are type IR01. Pyrgeometers are not classified by the ISO or WMO. The atmospheric LWin radiation essentially consists of two components: 1 Low temperature radiation from the universe, filtered by the atmosphere.
NR01 Four-Component Net Radiation Sensor TABLE 2.5-1. Average Global Radiation Values at the Earth Surface Type SW in SW out SW net LW in LW out LW net Net Units W/m2 W/m2 W/m2 W/m2 W/m2 W/m2 W/m2 Value 198 - 30 168 324* -390** -66 102 * LW in value assumes a sky temperature of 2ºC. ** LW out value assumes a surface temperature of 14ºC. NOTE The LW radiation values in Table 2.5-1 are corrected for sensor temperature. The values in Table 2.
NR01 Four-Component Net Radiation Sensor #Outputs listed for both of the pyrgeometers are not compensated for sensor temperature. For example, to correct for sensor temperature when the sensor temperature is 14 ºC, you should add 385 W/m2 to the pyrgeometer signals. The raw reading of the upward facing pyrgeometer will generally be close to zero when the sensor temperature is close to the ground temperature. You should expect small negative readings when the sensor is located above cooled surfaces (e.g.
NR01 Four-Component Net Radiation Sensor 3.1 NR01 General Specifications TABLE 3.1-1.
NR01 Four-Component Net Radiation Sensor 3.2 SR01 Pyranometer Specifications TABLE 3.2-1. Specifications of SR01 SR01 ISO / WMO Specifications Overall classification according to ISO 9060 / WMO Second class pyranometer Response time for 95 % response 18 s Zero offset a (response to 200 W/m2 net thermal radiation) < 15 W/m2 Zero offset b (response to 5 k/h change in ambient temperature) <4 W/m2 Non-stability < 1% change per year Non-Linearity < +/- 2.
NR01 Four-Component Net Radiation Sensor 3.3 IR01 Pyrgeometer Specifications TABLE 3.3-1. Specifications of IR01 IR01 Specifications Overall classification according to ISO / WMO Not applicable Response time for 95 % response 18 s Window heating offset (response to 1000 W/m2 net thermal radiation) < 15 W/m2 Zero offset b (response to 5 k/h change in ambient temperature) <4 W/m2 Non-Stability < 1% change per year Non-Linearity < +/- 2.
NR01 Four-Component Net Radiation Sensor 3.4 Dimensions 263 mm 027 mm (3/4 inch NPS) FIGURE 3.4-1. Dimensions of the NR01 in mm: (1) 2-Axis Leveling Assembly, (2) Mounting Arm 4. Installation 4.1 Installation A 1” to ¾” pipe reducer fitting (P/N 21271) is used for mounting the NR01 onto a CM204 or CM206 crossarm. The crossarm can be mounted to any pole with a 25-mm to 54-mm outer diameter.
NR01 Four-Component Net Radiation Sensor FIGURE 4.1-1. NR01 with Reducer (P/N 21271) and Mounting Arm TABLE 4.1-1. Recommendations for Installation of the NR01 Location Location of measurement should be representative of the total surrounding area, in particular in case the NR01 is used for environmental net radiation measurements. If possible, mount the sensor on a separate pole at least 25 ft away from main logger tower or tripod.
NR01 Four-Component Net Radiation Sensor 4.2 Electrical Connections The NR01 is a passive sensor that does not need any power. However there is an on-board heating resistor in the pyrgeometer connection body that may be switched on to prevent dew deposition. Cables generally act as a source of signal distortion by picking up capacitively coupled noise. Campbell Scientific generally recommends keeping the distance between the datalogger and sensor as short as possible. For cable extension, see Appendix A.
NR01 Four-Component Net Radiation Sensor TABLE 4.2-1.
NR01 Four-Component Net Radiation Sensor TABLE 4.3-1.
NR01 Four-Component Net Radiation Sensor The PT-100 sensor can connect directly to the CR3000 and CR5000 dataloggers because they have current excitation outputs. Refer to Table 4.3-4 and Program Example 5.2.2 for information on using the current excitation technique with a CR3000 or CR5000 datalogger. TABLE 4.3-4.
NR01 Four-Component Net Radiation Sensor 4.4 Installation of the Radiation Shields Radiation shields can be installed and removed using a hex-head wrench (bolt size 2.0 mm). See the drawing below. Radiation shields are beneficial for instrument measurement accuracy and instrument and cable lifetime. They also serve as rain- and snow shield. However, the instrument should function within specifications without the radiation shield. FIGURE 4.4-1.
NR01 Four-Component Net Radiation Sensor For the CR3000 and CR5000 dataloggers, one differential channel and a current excitation channel are used 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. FIGURE 5-1. 4WPB100 Module NOTE If free channels are limited it is possible to measure the PT100 sensor using a 3WHB10K terminal input module, with only a slight loss of accuracy.
NR01 Four-Component Net Radiation Sensor 5.2 Example Programs 5.2.1 Example 1, CR1000 Using Differential Channels Program Example 1 requires six differential channels and the 4WPB100 module to measure the four radiation outputs and the Pt-100 temperature sensor, connected on differential channels 1..6.
NR01 Four-Component Net Radiation Sensor Pt-100 Temperature Sensor Connections to 4WPB100 and Datalogger Color Function Black 4WPB100 CR1000 Wire EX1 H 5H 5L Red Pt-100 Excitation + L Blue Pt-100 Excitation - G White Pt-100 Signal + 6H Green Pt-100 Signal - 6L 'CR1000 'Declare Variables and Units Public Batt_Volt Public SR01Up Public SR01Dn Public IR01Up Public IR01Dn Public NR01TC Public NR01TK Public NetRs Public NetRl Public Albedo Public UpTot Public DnTot Public NetTot Public IR01
NR01 Four-Component Net Radiation Sensor ‘So load the four calibration coefficients specific to this sensor (1000/Sensitivity) Const SR01Upcal = 65.146 Const SR01Downcal = 75.18 Const IR01Upcal = 117.65 Const IR01Downcal = 121.
NR01 Four-Component Net Radiation Sensor 5.2.2 Example 2, CR3000/CR5000 Using Differential Channels (no 4WPB100) Program Example 2 requires five differential channels and one current excitation channel to measure the four radiation outputs and the Pt-100 temperature sensor. Connection details are given in the header of the program below.
NR01 Four-Component Net Radiation Sensor Public NetRs Public NetRl Public Albedo Public UpTot Public DnTot Public NetTot Public IR01UpCo Public IR01DnCo Units Batt_Volt = Volts Units SR01Up = W/m2 Units SR01Dn = W/m2 Units IR01Up = W/m2 Units IR01Dn = W/m2 Units NR01TC = Deg C Units NR01TK = K Units NetRs = W/m2 Units NetRl = W/m2 Units Albedo = W/m2 Units UpTot = W/m2 Units DnTot = W/m2 Units NetTot = W/m2 Units IR01UpCo = W/m2 Units IR01DnCo = W/m2 'Load the four calibration coefficients specific to this
NR01 Four-Component Net Radiation Sensor 'NR01 Net Radiometer measurements SR01Up, SR01Dn, IR01Up, IR01Dn, NR01TC, NR01TK, 'NetRs, NetRl, Albedo, UpTot, DnTot, NetTot, IR01UpCo, and IR01DnCo 'Uses fixed ranges as they fall more in line with the range of sensor outputs, so no need to 'autorange VoltDiff(SR01Up,1,mV50,1,True,200,250,SR01Upcal,0) VoltDiff(SR01Dn,1,mV50,2,True,200,250,SR01DownCal,0) VoltDiff(IR01Up,1,mV20,3,True,200,250,IR01Upcal,0) VoltDiff(IR01Dn,1,mV20,4,True,200,250,IR01DownCal,0) 'Note ma
NR01 Four-Component Net Radiation Sensor Avg Albedo Avg Total Net radiation Avg temperature corrected IR01 Up Avg temperature corrected IR01 Down ;{CR23X} ;Program Example 3 for CR23X datalogger ; ;*Table 1 Program 01: 2 Execution Interval (seconds) ;Measure all four sensor elements with one instruction, use auto-ranging for best resolution 1: Volt (Diff) (P2) 1: 4 Reps 2: 30 Auto, 50 Hz Reject, Slow Range (OS>1.06) 3: 1* DIFF Channel 4: 1 Loc [ SR01_up ] 5: 1.0 Multiplier 6: 0.
NR01 Four-Component Net Radiation Sensor 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.
NR01 Four-Component Net Radiation Sensor ; IR01_upCor = IR01_up+5.67 ; IR01_dnCor = IR01_dn+5.67 10-8 Temp_K4 10-8 Temp_K4 12: Z=F (P30) 1: 5.
NR01 Four-Component Net Radiation Sensor 5.2.4 Example 4, CR23X Program Using Single-Ended Channels Program Example 4 requires four single-ended channels to measure the four radiation outputs, and four single-ended channels and one differential channel for the 4WPB100 module to measure the Pt-100 temperature sensor. Wiring is as in Table 4.3-2, using SE channels 1..4 and 4.5 above using differential channel 3 and 4 for the PT100 sensor.
NR01 Four-Component Net Radiation Sensor 2: Scaling Array (A*Loc+B) (P53) 1: 1 Start Loc [ SR01_up ] 2: 65.146 A1 3: 0 B1 4: 75.18 A2 5: 0.0 B2 6: 117.65 A3 7: 0.0 B3 8: 121.95 A4 9: 0.0 B4 ;SR01 up ;SR01 down ;IR01 up ;IR01 down ;Measure the IR01 temperature 3: Full Bridge w/mv Excit (P9) 1: 1 Reps 2: 32 50 mV, 50 Hz Reject, Slow, Ex Range** 3: 32 50 mV, 50 Hz Reject, Slow, Br Range** 4: 3* DIFF Channel 5: 1 Excite all reps w/Exchan 1 6: 4200 mV Excitation*** 7: 5 Loc [ IR01_TC ] 8: 1 Multiplier 9: 0.
NR01 Four-Component Net Radiation Sensor 6. Maintenance and Troubleshooting 6.1 Maintenance Once installed the NR01 is essentially maintenance free apart from cleaning dirt off the domes every few weeks. Usually errors in functionality will appear as unreasonably large or small measured values. As a general rule, this means that a critical review of the measured data is the best form of maintenance. At regular intervals the quality of the cables can be checked.
NR01 Four-Component Net Radiation Sensor 6.2 Troubleshooting This table contains information used to diagnosis problems whenever the sensor does not function properly. TABLE 6.2-1. Troubleshooting for the NR01 The sensor does not give any signal Typically an error is due to either a short circuit or an open connection. Both can be detected by impedance / resistance measurements at the cable end.
Appendix A. CR3000 Program that Controls the Heater This program applies power to the NR01 heater using the SW12V relay controller and the pulse width modulation instruction (PWM ()). Rather than using 0 degrees C as a set point for the heater, the program below uses the dew point value. The datalogger calculates dew point using the relative humidity (RH) measurements provided by the HMP45C Temperature/Relative Humidity probe.
Appendix A.
Appendix A. CR3000 Program that Controls the Heater Alias nr01(5) = Rl_downwell Alias nr01(6) = Rl_upwell Alias nr01(7) = t_nr01 Alias nr01(8) = Rl_down_meas Alias nr01(9) = Rl_up_meas Units panel_temp = C Units batt_volt = V Units t_hmp = C Units rh_hmp = percent Units e_hmp = kPa Units nr01 = W/m^2 Units albedo = unitless Units t_nr01 = K 'Net radiometer heater control variables.
Appendix A. CR3000 Program that Controls the Heater BeginProg Scan (1,Sec,0,0) 'Control the net radiometer heater. PWM (duty_cycle,4,250,mSec) 'Datalogger panel temperature. PanelTemp (panel_temp,250) 'Measure battery voltage. Battery (batt_volt) 'Measure the HMP45C temperature and relative humidity. VoltDiff (t_hmp,1,mV1000C,5,TRUE,200,250,0.1,-40) VoltDiff (rh_hmp,1,mV1000C,6,TRUE,200,250,0.1,0) 'Measure NR 01 Net Radiometer.
Appendix A. CR3000 Program that Controls the Heater Case Is < ( set_point_temperature+DELTA_SET_POINT_1+DELTA_SET_POINT_2 ) duty_cycle = MAX_DUTY_CYCLE_2+(t_nr01(t_dew_hmp_mean+273.15+DELTA_SET_POINT_1))*SLOPE_2 Case Else duty_cycle = 0.01 EndSelect Else duty_cycle = 0.
Appendix A.
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