NR-LITE Net Radiometer Revision: 5/10 C o p y r i g h t © 1 9 9 8 - 2 0 1 0 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 NR-LITE 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.
NR-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...................................................................................2 1.2 Spectral Properties .....................................................................................2 1.3 Directional/Cosine Response..
NR-LITE Table of Contents Tables 1. Datalogger Connections for Differential Measurement ............................. 8 2. Datalogger Connections for Single-Ended Measurement..........................
NR-LITE Net Radiometer The NR-LITE is a high-output thermopile sensor which measures the algebraic sum of incoming and outgoing all-wave radiation (i.e. both short-wave and long-wave components). Incoming radiation consists of direct (beam) and diffuse solar radiation plus long-wave irradiance from the sky. Outgoing radiation consists of reflected solar radiation plus the terrestrial long-wave component. The NR-LITE is equipped with Teflon-coated sensor surfaces.
NR-LITE Net Radiometer 1.1 Electrical Properties The thermopile consists of a number of thermocouples connected in series, essentially providing a highly sensitive differential temperature sensor. The thermopile generates a voltage output – the sensor itself is passive, and so no power supply is required. The upwards and downwards facing sensor surfaces are connected to the upper and lower thermopile junctions respectively, and so the sensor can measure the differential temperature.
NR-LITE Net Radiometer FIGURE 3. Approximate Spectral Sensitivity and Solar/F.I.R. Radiation The upwards facing sensor is calibrated for solar radiation wavelengths. The following assumptions are made: • It is assumed that the downwards facing sensor has the same sensitivity. However, since the two sensors may not be perfectly symmetrical, this assumption may not always be true, but any differences are small.
NR-LITE Net Radiometer FIGURE 4. Cosine Response of a Typical Net Radiometer 1.4 Sensitivity to Wind Speed The calibration of the NR-LITE is carried out at zero wind speed. At any other wind speed the sensitivity will decrease. It has been shown that this decrease in sensitivity is less than 1% of reading per meter per second wind speed, and the effect is essentially independent of the radiation level.
NR-LITE Net Radiometer FIGURE 5. NR-LITE Wind Sensitivity 2. Sensor Specifications Spectral Spectral range: Detector type: Detector protection: Detector profile: 0.2 to 100 μm Thermopile Teflon coating Conical Directional Directional error: (0 - 60° at 1000 W m-2): Sensor asymmetry: <30 W m-2 ±5% typical, (±10% worst case).
NR-LITE Net Radiometer Mechanical Housing material: Cable material: Weight: Cable length: Physical Dimensions Sensor: Support Arm: Weight: Anodized aluminum Polyurethane 200 g 15 m (can be extended up to 100 m) 3.1” (8.0 cm) diameter 0.6” (1.6 cm) diameter x 31.5” (80 cm) L 23 oz (635 g) Environmental Working temperature: -30 to +70°C Temperature dependence: 0.12%/°C 3. Installing the NR-LITE NOTE Screw in the ~2.
NR-LITE Net Radiometer Support Arm 26120 Pole 26120 Support Arm Crossarm FIGURE 6. Mounting the NR-LITE onto a pole (top) and crossarm (bottom) via the 26120 Mounting Kit.
NR-LITE Net Radiometer 4. Wiring The NR-LITE can be measured with a differential or single-ended channel on the datalogger; a differential channel is recommended. White Radiation Signal Green Signal Reference (User supplied jumper wire for differential measurement only) Clear Shield FIGURE 7. NR-Lite to Datalogger Connections TABLE 1.
NR-LITE Net Radiometer 5. Datalogger Programming NOTE This section is for users who write their own datalogger programs. A datalogger program to measure this sensor can be generated using Campbell Scientific’s Short Cut Program Builder Software. You only need to read the calibration portion of this section if using Short Cut. The NR-LITE outputs a low-level voltage ranging from 0 to a maximum of about 15 mV.
NR-LITE Net Radiometer 5.3 Example Programs 5.3.1 CR3000 Example Program without Wind Speed Correction Shown below is an example program written for the CR3000 datalogger. The datalogger measures the output from the sensor every 5 seconds and outputs the average net radiation every hour. The calibration factor used will only apply for one specific sensor. A new value will need to be calculated for every different sensor based on the certificate of calibration for that sensor (see Section 5.2).
NR-LITE Net Radiometer 5.3.2 CR1000 Example Program with Wind Speed Correction Shown below is an example program written for the CR1000 datalogger. Besides measuring the NR-LITE, the program also measures wind speed and applies the correction factor as described in Section 1.4. Average net radiation and wind speed are output every hour.
NR-LITE Net Radiometer '05103 Wind Speed & Direction Sensor measurements WS_ms and WindDir PulseCount(WS_ms,1,1,1,1,0.098,0) BrHalf(WindDir,1,mV2500,1,1,1,2500,True,0,_60Hz,355,0) If WindDir>=360 Then WindDir=0 'NR-LITE Net Radiometer (dynamic wind speed correction) 'measurement NR_Wm2 and CNR_Wm2 VoltDiff(NR_Wm2,1,mv25,2,True,0,_60Hz,100,0) If WS_ms>=5 Then CNR_Wm2=NR_Wm2*(1+0.
NR-LITE Net Radiometer 2: 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) 3: Real Time (P77) 1: 110 Day,Hour/Minute (midnight = 0000) 4: Average (P71) 1: 1 2: 1 Reps Loc [ Net_rad ] 5.3.4 CR10X Example Program with Wind Speed Correction This example measures the NR-LITE using a single-ended input and Instruction 1. The program also measures wind speed and applies the correction factor as described in Section 1.4.
NR-LITE Net Radiometer ;apply wind speed correction factor ;Rn,cor = Rn,obs*(1.0+0.021286*(U-5.0)) when U > 5 m/s 3: If (X<=>F) (P89) 1: 1 X Loc [ Wspd_m_s ] 2: 3 >= 3: 5 F 4: 30 Then Do 4: Z=X+F (P34) 1: 1 2: -5 3: 24 X Loc [ Wspd_m_s ] F Z Loc [ scratch_1 ] 5: Z=X*F (P37) 1: 24 2: .
NR-LITE Net Radiometer 6. Maintenance The radiometer 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. The NR-LITE should be recalibrated every two years. Contact CSI for an RMA number before returning the sensor for recalibration. 7. Troubleshooting 7.
NR-LITE Net Radiometer • Put your hand over the upper sensor. Assuming that your hand is at a higher temperature than the sensor the positive reading should increase. Conversely, if the sensor is warmer than your hand the reading will decrease. • Check the radiometer’s sensitivity to thermal shocks by touching the edge of the sensor (the blank metal) with your hand for some seconds. The resultant shock will result in a signal drift, or a zero offset that will take some time to settle back to zero.
Campbell Scientific Companies Campbell Scientific, Inc. (CSI) 815 West 1800 North Logan, Utah 84321 UNITED STATES www.campbellsci.com • info@campbellsci.com Campbell Scientific Africa Pty. Ltd. (CSAf) PO Box 2450 Somerset West 7129 SOUTH AFRICA www.csafrica.co.za • cleroux@csafrica.co.za Campbell Scientific Australia Pty. Ltd. (CSA) PO Box 444 Thuringowa Central QLD 4812 AUSTRALIA www.campbellsci.com.au • info@campbellsci.com.au Campbell Scientific do Brazil Ltda.
