Campbell CNR4 User Manual
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Campbell CNR4 User Manual

Net radiometer
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CNR4
CNR4
Net Radiometer
Issued: 29.7.13
Copyright © 2000-2013 Campbell Scientific, Inc.
Printed under licence by Campbell Scientific Ltd.
CSL 874

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  • Page 1 CNR4 CNR4 Net Radiometer Issued: 29.7.13 Copyright © 2000-2013 Campbell Scientific, Inc. Printed under licence by Campbell Scientific Ltd. CSL 874...
  • Page 3 Quotations for repairs can be given on request. It is the policy of Campbell Scientific to protect the health of its employees and provide a safe working environment, in support of this policy a “Declaration of Hazardous Material and Decontamination”...

  • Page 5: About This Manual

    PLEASE READ FIRST About this manual Please note that this manual was originally produced by Campbell Scientific Inc. primarily for the North American market. Some spellings, weights and measures may reflect this origin. Some useful conversion factors: Area: 1 in (square inch) = 645 mm 1 oz.

  • Page 7: Table Of Contents

    2.4.1 CNF4 Specifications ............... 6 3. Installation ..............6 4. Using the Optional CNF4 Heater/Ventilator Unit ..8 5. Using the CNR4 in the Four Separate Components Mode ............ 9 5.1 Measuring Short-wave Solar Radiation with Pyranometer ...... 9 5.2 Measuring Long-wave Far Infrared Radiation with Pyrgeometer ... 9 5.3 Measuring CNR4 Temperature with Thermistor ........
  • Page 8 ..............8 6-1. The CNR4 sensor with SOLAR and TEMP cables ....... 14 6-2. The marks on the end of the CNR4: S for SOLAR cable, and T for TEMP cable ..................14 6-3. Labels on the pigtail end of the SOLAR cable........15 6-4.
  • Page 9 Tables 5-1. Resistance values versus CNR4's thermistor temperature in °C ... 11 5-2. Resistance values versus CNR4's Pt-100 temperature in °C ....12 6-1. Datalogger Connections for Differential Measurement ......16 6-2. Datalogger Connections for Single-ended Measurement ..... 16 A-1. Typical output signals of CNR4 under different meteorological conditions.

  • Page 11: General Description

    The upper long-wave detector of CNR4 has a meniscus dome. This ensures that water droplets roll off easily and improves the field of view to nearly 180°, compared with a 150° for a flat window.

  • Page 12: Sensor Specifications

    CNF4. 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.

  • Page 13: Cnr4 Specifications

    User Manual Figure 2-2. The CNR4 net radiometer with CNF 4 heater/ventilator unit, top view. 2.1 CNR4 Specifications Four probes have unique sensitivity Sensor sensitivities: values. Please refer to the calibration sheets or label on the bottom of the sensor for the sensitivity values.

  • Page 14: Pyranometer Specifications

    CNR4 Net Radiometer WRR Traceable Calibration Certificate for pyranometers WRR Traceable Calibration Certificate for pyrgeometers Extra Calibration Sticker (to be put on CNF4, if used) CNF4 Heater/Ventilator CNF4 Package includes: CNF4 cable 2.2 Pyranometer Specifications * indicates ISO specifications. 305 to 2800 nm (50% points) Spectral range: 10 to 20 µV/W/m...

  • Page 15: Pyrgeometer Specifications

    User Manual Typical signal output for 0 to 15 mV atmospheric application: 20 to 200 Ω, typically 50Ω Impedance: Copper-constantan multi junction Detector: thermopile 1 degree Level accuracy: 0 to 2000 W/m Irradiance: < 3% (330-1500 nm spectral interval) Spectral selectivity: <...

  • Page 16: Optional Cnf4 Heater/Ventilator

    Hemisphere this implies that the net radiometer should be mounted south of the mast. It is suggested that the CNR4 is mounted at a height of at least 1.5 metres above the surface to avoid shading effects of the instruments on the soil and to promote spatial averaging of the measurement.

  • Page 17: The Cnr4 Net Radiometer With Cnf 4 Heater/Ventilator Unit, Top View . 3 3-1. Attaching The Mounting Rod To The Cnr4 Body

    Perform a coarse levelling of the sensor using the bubble level on the top of the CNR4, and tighten the four screws on top of the mounting bracket to properly secure the mounting rod so that it does not rotate.

  • Page 18: Using The Optional Cnf4 Heater/Ventilator Unit

    For installation in buildings or in solar energy applications, one will often have to mount the CNR4 parallel to the surface that is being studied. This may be in a tilted or a vertical position. The sensitivity of the radiometers will be affected, but only in a minor way.

  • Page 19: Using The Cnr4 In The Four Separate Components Mode

    T, into account. This is why the temperature sensors are incorporated in the CNR4's body near the pyrgeometer sensing element, and has, therefore, the same temperature as the pyrgeometer sensor surface. The...

  • Page 20: Measuring Cnr4 Temperature With Thermistor

    Table 5-1 shows the thermistor resistance values as a function of temperature. Relatively small errors occur when the CNR4 is not in thermal equilibrium. This happens for example when the heater is on, or when the sun is shining. When the heater and ventilator are on, the largest expected deviation between the real sensor temperature and the thermistor reading is 1 degree.

  • Page 21: Resistance Values Versus Cnr4'S Thermistor Temperature In °C

    Pt-100 sensor, you will need one current excitation channel, and one differential analogue channel. Please refer to Appendix C for a sample program to measure Pt-100. Table 5-1. Resistance values versus CNR4's thermistor temperature in °C. Temperature Resistance...

  • Page 22: Calculation Of Albedo

    CNR4 Net Radiometer Table 5-2. Resistance values versus CNR4's Pt-100 temperature in °C. Temperature Resistance Temperature Resistance Temperature Resistance [°C] [°C] [°C] [Ω] [Ω] [Ω] 88.22 100.00 111.67 112.06 88.62 100.39 89.01 100.78 112.45 112.83 89.40 101.17 89.80 101.56 113.22 101.95...

  • Page 23: Calculation Of Net Short-Wave Radiation

    Therefore, if one is only interested in the net long-wave radiation, instead of separate upper and lower components of the long-wave radiation, the CNR4 temperature measurement is not required. The E measured with the pyrgeometer actually represents the irradiance of the sky (for the upward- facing pyrgeometer) or the ground (for the downward-facing pyrgeometer).

  • Page 24: Wiring

    Figure 6-1. The CNR4 sensor with SOLAR and TEMP cables. Figure 6-2. 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...

  • Page 25: Labels On The Pigtail End Of The Solar Cable

    User Manual 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. When differential inputs are used, jumper the low side of the input NOTE to AG or to keep the signal in common mode range.

  • Page 26: Datalogger Programming

    Clear 7. 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.

  • Page 27: Sensor Sensitivity

    7.1 Sensor Sensitivity Unlike the CNR1, the CNR4 comes with four different sensor sensitivity values for four separate probes. The CNR4 sensor comes with two copies of ‘Certificate of Calibration’ by the manufacturer that show the sensor serial number and sensitivity values for four individual probes: one for pyranometers, and another for pyrgeometers.
  • Page 28 '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.
  • Page 29 Units albedo = W/m^2 Units 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 pyranometer_up_sensitivity = 15.35 'unique sensitivity for upper pyranometer '(microV/W/m^2) Const pyranometer_dn_sensitivity = 15.41...
  • Page 30 EndTable DataTable (cnr4_ts,True,-1) DataInterval (0,1,Sec,10) CardOut (1,-1) Sample (4,cnr4(1),IEEE4) Sample (1,cnr4_T_K,IEEE4) EndTable BeginProg 'Load the multiplier values for the CNR4 cnr4_mult(1) = pyranometer_up_mult cnr4_mult(2) = pyranometer_dn_mult cnr4_mult(3) = pyrgeometer_up_mult cnr4_mult(4) = pyrgeometer_dn_mult Scan (1,Sec,3,0) PanelTemp (logger_temp,250) Battery (batt_volt) 'CNR4 radiation measurements...

  • Page 31: Example 2, Cr3000 Program Using Differential Measurements

    60 minutes. It also stores the raw time-series data from CNR4 to data table called cnr4_ts. Minimum Battery voltage...
  • Page 32 CNR4 Pyranometer Upper signal (red) CNR4 Pyranometer Upper signal reference (blue) 'gnd jumper to 1L CNR4 Pyranometer Lower signal (white) CNR4 Pyranometer Lower signal reference (thin black) 'gnd jumper to 2L CNR4 Pyrgeometer Upper signal (grey) CNR4 Pyrgeometer Upper signal reference (yellow)
  • Page 33 User Manual 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 pyranometer_up_sensitivity = 15.35 'unique sensitivity for upper pyranometer '(microV/W/m^2) Const pyranometer_dn_sensitivity = 15.41...

  • Page 34: Example 3, Cr5000 Program Using Differential Measurements

    60 minutes. It also stores the raw time- series data from CNR4 to data table called cnr4_ts. The variables for the CR5000 datalogger can be up to 16 characters NOTE in length.
  • Page 35 '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.
  • Page 36 Units albedo = W/m^2 Units 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 = 15.41...
  • Page 37 EndTable DataTable (cnr4_ts,True,-1) DataInterval (0,1,Sec,10) CardOut (1,-1) Sample (4,cnr4(1),IEEE4) Sample (1,cnr4_T_K,IEEE4) EndTable BeginProg 'Load the multiplier values for the CNR4 cnr4_mult(1) = pyra_up_mult cnr4_mult(2) = pyra_dn_mult cnr4_mult(3) = pyrg_up_mult cnr4_mult(4) = pyrg_dn_mult Scan (1,Sec,3,0) PanelTemp (logger_temp,250) Battery (batt_volt) 'CNR4 radiation measurements...

  • Page 38: Troubleshooting

    CNR4 Net Radiometer 8. Troubleshooting If there is no indication as to what may be the problem, start performing the following "upside-down test", which is a rough test for a first diagnosis. It can be performed both outdoors and indoors. Indoors, a lamp can be used as a source for both short-wave and long-wave radiation.

  • Page 39: Testing The Thermistor

    User Manual The CNR4 body and ambient air should be at the same temperature as much as possible. Let the pyrgeometer rest for at least five minutes to regain its thermal equilibrium. Set the voltmeter to its most sensitive range. To test if the pyrgeometer is working properly, we suggest putting your hand in front of the pyrgeometer.

  • Page 40: Replacing The Drying Cartridge

    Please contact Campbell Scientific, to obtain an RMA number for recalibration. 9.3 Replacing the Drying Cartridge The CNR4 has a drying cartridge inside the sensor to help keep the electronics dry. The manufacturer recommends that this drying cartridge be replaced every 6 to 12 months.
  • Page 41 This can roughly be attributed to the water vapour in the air, which is a major contributor to the far infrared radiation. Table A-1. Typical output signals of CNR4 under different meteorological conditions. Explanation can be found in the text.

  • Page 42: A-1. Different Measurement Conditions And Signals

    CNR4 Net Radiometer Figure A-1. Different measurement conditions and signals. Upper pyrgeometer Day with alternating cloud fields  pyrgeometer:  U_emf / Sensitivity [W/m²] Temp YSI 44031 [°C] ‐10 ‐20 ‐30 ‐40 ‐50 ‐60 ‐70 ‐80 ‐90 ‐100 ‐110 ‐120 ‐130 ‐140 ‐150 ‐160 ‐170 ‐180 Figure A-2. Partly cloudy day for the upward facing pyrgeometer.

  • Page 43: Cnr4 Performance And Measurements Under Different Conditions

    Appendix A. CNR4 Performance and Measurements under Different Conditions upwelling signal (downward facing) pyrgeometer Pyrgeometer: U‐emf / sensitivity [W/m²] Temp of instrument [°C] ‐10 ‐20 ‐30 Figure A-3. Clear day for the downward facing pyrgeometer. It is assumed that when ambient temperature varies, the net far infrared radiation remains roughly the same, independent of ambient temperature. The resulting measured values of the pyrgeometers and pyranometers are shown in columns 4 to 7.
  • Page 44 CNR4 Net Radiometer upper ⎡ ⎤ Sky temper ature ⎢ ⎥ − ⋅ ⎣ ⎦ (B-1) lower ⎡ ⎤ Ground Temperatur ⎢ ⎥ − ⎣ ⋅ ⎦ (B-2)

  • Page 45: Cnf4 Heater/Ventilator

    Appendix B. CNF4 Heater/Ventilator Whenever the heater is used, the hea ting may cause errors in th e NOTE measurement of the sensor temperature. Under most conditions the accuracy that is gained by heating will be larger than the errors that are introduced by heating.

  • Page 46: Attaching The Optional Cnf4 Heater/Ventilator Unit To Cnr4

    Appendix B. CNF4 Heater/Ventilator 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). The ventilator draws additional 5 Watts of power at 12 Vdc.

  • Page 47: B-2. Attaching The Cnf4 To Cnr4 Using Pan-Head Screws And Washers

    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.

  • Page 48: B-3. Making Sure The Cables Are Clear From The Edges

    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 flat-head screws provided to complete the solar shield installation to the CNF4, as shown in Figure B-4 and B-5.

  • Page 49: 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...

  • Page 50: Wiring

    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. CR1000 and CR3000 Datalogger Connections for Differential Measurement with Heater/Ventilator Control...
  • Page 51 'CR3000 Series Datalogger 'CNR4 program 'This program measures CNR4 four-component net radiometer 'This program also measures the thermistor inside the CNR4 'In addition this program controls heater and ventilator ' using separate SW12V-1 and SW12V-2 channels 'The heater and ventilator are turned on/off by setting flag(1), and flag(2) high and low, respectively.
  • Page 52 Units albedo = W/m^2 Units 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 pyranometer_up_sensitivity = 15.35 'unique sensitivity for upper pyranometer '(microV/W/m^2) Const pyranometer_dn_sensitivity = 15.41...
  • Page 53 EndTable DataTable (cnr4_ts,True,-1) DataInterval (0,1,Sec,10) CardOut (1,-1) Sample (4,cnr4(1),IEEE4) Sample (1,cnr4_T_K,IEEE4) EndTable BeginProg 'Load the multiplier values for the CNR4 cnr4_mult(1) = pyranometer_up_mult cnr4_mult(2) = pyranometer_dn_mult cnr4_mult(3) = pyrgeometer_up_mult cnr4_mult(4) = pyrgeometer_dn_mult Scan (1,Sec,3,0) anelTemp (logger_temp,250) attery (batt_volt) 'CNR4 radiation measurements...

  • Page 54: Cnf4 Heater/Ventilator Maintenance

    The filter can be cleaned with warm clean water, or can be replaced with the new one. You can purchase the replacement filters from Campbell Scientific (P/N #26010, a set of 5). B-10...

  • Page 55: Cr3000 Program For Measuring Pt-100

    Measuring Pt-100 Temperature Sensor The program 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, and one current excitation channel and one differential channel for Pt-100 measurement.
  • Page 56 '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.
  • Page 57 Units albedo = W/m^2 Units Rn = W/m^2 Dim cnr4_prt_R, Rs_R0 'CNR4 sensitivities: refer to the Certificate of Calibration from Kipp & Zonen for sensitivity values 'for each probes, and enter them below. Const pyranometer_up_sensitivity = 15.35 'unique sensitivity for upper pyranometer '(microV/W/m^2) Const pyranometer_dn_sensitivity = 15.41...
  • Page 58 CNR4 Net Radiometer DataTable (cnr4_ts,True,-1) DataInterval (0,1,Sec,10) CardOut (1,-1) Sample (4,cnr4(1),IEEE4) Sample (1,cnr4_T_K,IEEE4) EndTable BeginProg 'Load the multiplier values for the CNR4 cnr4_mult(1) = pyranometer_up_mult cnr4_mult(2) = pyranometer_dn_mult cnr4_mult(3) = pyrgeometer_up_mult cnr4_mult(4) = pyrgeometer_dn_mult Scan (1,Sec,3,0) PanelTemp (logger_temp,250) Battery (batt_volt)
  • Page 60 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 • sales@csafrica.co.za Campbell Scientific Australia Pty. Ltd. (CSA)

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