Campbell Scientific CNR4 User Manual
CNR4 Net Radiometer
Revision: 9/13
Copyright © 2000-2013
Campbell Scientific, Inc.
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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. Quickstart .................................................................... 2
4.1 Siting Considerations ...........................................................................2
4.2 Mounting..............................................................................................2
4.3 Use SCWin to Program Datalogger and Generate Wiring Diagram....4
5. Overview......................................................................7
6. Specifications .............................................................8
6.1 CNR4 Specifications..........................................................................10
6.2 Pyranometer Specifications................................................................10
6.3 Pyrgeometer Specifications................................................................11
6.4 Optional CNF4 Heater/Ventilator ......................................................12
6.4.1 CNF4 Specifications ...................................................................12
7. Operation...................................................................13
7.1 Using the CNR4 in the Four Separate Components Mode.................13
7.1.1 Measuring Short-wave Solar Radiation with Pyranometer.........13
7.1.2 Measuring Long-wave Far Infrared Radiation with
Pyrgeometer.............................................................................13
7.1.3 Measuring CNR4 Temperature with Thermistor ........................14
7.1.4 Calculation of Albedo .................................................................16
7.1.5 Calculation of Net Short-wave Radiation ...................................17
7.1.6 Calculation of Net Long-wave Radiation....................................17
7.1.7 Calculation of Net (Total) Radiation...........................................18
7.2 Wiring ................................................................................................18
7.3 Datalogger Programming...................................................................21
7.3.1 Sensor Sensitivity........................................................................21
7.3.2 Example Programs......................................................................21
7.3.2.1 Example 1, CR1000 Program Using Differential
Measurements...............................................................21
7.3.2.2 Example 2, CR3000 Program Using Differential
Measurements...............................................................24
7.3.2.3 Example 3, CR5000 Program Using Differential
Measurements...............................................................27
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Table of Contents
8. Troubleshooting........................................................30
8.1 Testing the Pyranometer.................................................................... 30
8.2 Testing the Pyrgeometer.................................................................... 31
8.3 Testing the Thermistor ...................................................................... 31
8.4 Testing the Pt-100 ............................................................................. 31
9. Maintenance and Recalibration ...............................32
9.1 Cleaning Windows and Domes ......................................................... 32
9.2 Recalibration ..................................................................................... 32
9.3 Replacing the Drying Cartridge......................................................... 32
9.4 Replacement Parts ............................................................................. 33
Appendices
CNR4 Performance and Measurements under
A.
Different Conditions .............................................A-1
B. CNF4 Heater/Ventilator ...........................................B-1
B.1 General Information ........................................................................ B-1
B.2 Attaching the Optional CNF4 Heater/Ventilator Unit to CNR4...... B-3
B.3 Wiring.............................................................................................. B-7
B.4 Example B, CR3000 Datalogger Program with Heater/
Ventilator Control ........................................................................ B-8
B.5 CNF4 Heater/Ventilator Maintenance........................................... B-11
B.5.1 Testing the Heater .................................................................. B-11
B.5.2 Testing the Ventilator............................................................. B-11
B.5.3 Replacing the Filter for the Ventilator.................................... B-11
C. CR3000 Program for Measuring Pt-100
Temperature Sensor............................................. C-1
Figures
4-1. Attaching the mounting rod to the CNR4 body................................... 2
4-2. Attaching the CNR4 onto the mounting rod (pn 26120) using
vertical pole or horizontal crossarm................................................. 3
6-1. The CNR4 net radiometer with cables and mounting rod, top view.... 9
6-2. The CNR4 net radiometer with CNF 4 heater/ventilator unit, top
view.................................................................................................. 9
7-1. The CNR4 sensor with SOLAR and TEMP cables........................... 18
7-2. The marks on the end of the CNR4: S for SOLAR cable, and T
for TEMP cable.............................................................................. 19
7-3. Labels on the pigtail end of the SOLAR cable.................................. 19
7-4. Labels on the pigtail end of the TEMP cable. ................................... 20
9-1. Replacing the drying cartridge .......................................................... 33
A-1. Different measurement conditions and signals................................ A-2
A-2. Partly cloudy day for the upward facing pyrgeometer..................... A-2
A-3. Clear day for the downward facing pyrgeometer ............................ A-3
B-1. CNF4 package contents................................................................... B-3
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Tables
Table of Contents
B-2. Attaching the CNF4 to CNR4 using pan-head screws and
washers .........................................................................................B-4
B-3. Making sure the cables are clear from the edges..............................B-5
B-4. CNF4 solar shield and four flat-head screws ...................................B-5
B-5. Attaching the solar shield to CNF4 using four flat-head screws......B-6
B-6. Affixing the sensor label to CNF4 ...................................................B-6
B-7. Connecting the CNF4 power control cable and the mounting rod ...B-6
7-1. Resistance values versus CNR4’s thermistor temperature in °C........14
7–2. Resistance values versus CNR4’s Pt–100 temperature in °C.............16
7-3. Datalogger Connections for Differential Measurement .....................20
7-4. Datalogger Connections for Single-Ended Measurement ..................20
A-1. Typical output signals of CNR4 under different meteorological
conditions. Explanation can be found in the text......................... A-1
B-1. CR1000 and CR3000 Datalogger Connections for Differential
Measurement with Heater/Ventilator Control ..............................B-7
C-1. Datalogger Connections for Differential Measurement with
Pt-100 ...........................................................................................C-1
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Table of Contents
iv
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:
• Section 2, Cautionary Statements
• Section 3, Initial Inspection
• Section 4, Quickstart
2. Cautionary Statements
• Although the CNR4 is rugged, it is also a highly precise scientific
instrument and should be handled as such.
• Care should be taken when opening the shipping package to not damage or
cut the cable jacket. If damage to the cable is suspected, consult with a
Campbell Scientific applications engineer.
• Do not attempt to rotate the instrument using the sensor heads, or you may
damage the sensors; use the mounting rod only.
3. Initial Inspection
• Upon receipt of the CNR4, inspect the packaging and contents for damage.
File damage claims with the shipping company.
• The model number and cable length are printed on a label at the
connection end of the cable. Check this information against the shipping
documents to ensure the correct product and cable length are received.
• Refer to the Ships With list to ensure that parts are included (see Section
3.1, Ships With).
3.1 Ships With
(2) 26006 Drying Cartridges
(1) WRR Traceable Calibration Certificate for the pyranometers
(1) WRR Traceable Calibration Certificate for the pyregeometers
(1) Mounting Arm from original manufacturer
(1) Extra Calibration Stickers from original manufacturer
(1) ResourceDVD
1
CNR4 Net Radiometer
4. Quickstart
4.1 Siting Considerations
Please review Section 7, Operation, for wiring and CRBasic programming.
Appendix B, CNF4 Heater/Ventilator, provides information about using the
CNF4 heater/ventilator.
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. 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 10h.
Shadows or surface disturbances with a radius < 0.1h will affect the
measurement by less than 1%.
2. To avoid shading effects and to promote spatial averaging, the CNR4
should be mounted at least 1.5 m above the ground surface. It is
recommended that the CNR4 be mounted to a separate vertical pipe at
least 25 ft from any other mounting structures.
3. Orient the sensor towards the nearest pole to avoid potential problems
from shading.
4.2 Mounting
A mounting bracket kit, pn 26120, is used to mount the CNR4 directly to a
vertical pipe, or to a CM202, CM203, CM204, or CM206 crossarm. Mount the
sensor as follows:
1. Attach the mounting rod to the CNR4 (see FIGURE 4-1).
FIGURE 4-1. Attaching the mounting rod to the CNR4 body
2
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).
CAUTION
FIGURE 4-2. Attaching the CNR4 onto the mounting rod
(pn 26120) using vertical pole or horizontal crossarm
3. 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).
Do not attempt to rotate the instrument using the sensor
heads, or you may damage the sensors; use the mounting
rod only.
4. Perform a coarse leveling of the sensor using the sensor’s bubble level.
5. Tighten the four screws on top of the mounting bracket to properly secure
the support arm so that it does not rotate (see FIGURE 4-2).
3
CNR4 Net Radiometer
4.3 Use SCWin to Program Datalogger and Generate Wiring Diagram
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.
The simplest method for programming the datalogger to measure the CNR4 is
to use Campbell Scientific’s SCWin Program Generator.
NOTE
The SCWin example provided here uses the thermistor to
provide the temperature correction.
1. Open Short Cut and click on New Program.
4
2. Select the datalogger and enter the scan interval.
CNR4 Net Radiometer
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.
5
CNR4 Net Radiometer
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.
6
CNR4 Net Radiometer
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.
5. 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. The upper longwave detector of CNR4 has a meniscus dome to ensure that water droplets roll
off easily while improving the field of view to nearly 180°, compared with a
150° for a flat window. All four sensors are integrated directly into the
instrument body, instead of separate modules mounted onto the housing. Each
sensor is calibrated individually for optimal accuracy.
Two temperature sensors, a thermistor and a Pt-100, are integrated with the
CNR4 body. The temperature sensor is used to provide information to correct
the infrared readings for the temperature of the instrument housing. Care has
been taken to place the long-wave sensors close to each other and close to the
temperature sensors. This ensures that the temperatures of the measurement
surfaces are the same and accurately known, improving the quality of the longwave measurements. A completion resistor is added in the pig tail end of the
thermistor cable providing an easy interface with dataloggers for half-bridge
measurement.
The CNR4 design is light weight and has an integrated solar shield that reduces
thermal effects on both the short-wave and the long-wave measurements. The
cables are made from Santoprene® jacket, which is intended for outdoor use,
7
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.
The CNR4 design is such that both the upward facing and the downwardfacing instruments measure the energy that is received from the whole
hemisphere (180° field of view). The output is expressed in W/m
spectral range that is measured is roughly from 0.3 to 42 μm. This spectral
range covers both the short-wave solar radiation, 0.3 to 2.8 μm, and the longwave far infrared radiation, 4.5 to 42 μm. The gap between these two produces
negligible errors.
The CNR4 is manufactured by Kipp & Zonen, but cabled for use with
Campbell Scientific dataloggers. Its cables can terminate in:
• Pigtails that connect directly to a Campbell Scientific datalogger
(cable termination option –PT).
• Connector that attaches to a prewired enclosure (cable termination
option –PW).
2
. The total
6. Specifications
Features:
Compatible Dataloggers: CR1000
CR3000
CR5000
• Research-grade performance
• Meniscus dome on upper long-wave detector allows water droplets to
easily roll off of it and increases field of view to nearly 180°
• Internal temperature sensors provide temperature compensation of
measurements
• Drying cartridge helps keep the electronics dry
• Compatible with the CNF4 ventilation unit with heater that reduces
formation of dew and melts frost
• Separate outputs of short-wave and long-wave infrared radiation for
better accuracy and more thorough quality assurance
• Solar shield reduces thermal effects on the sensors
8
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.
Due to the fact that the net short-wave radiation can be very intense, 1000
2
compared to a typical –100 W/m2 net long-wave radiation, the accuracy
W/m
of the short-wave radiation measurement is critical. Wind corrections, as
applied by less accurate competitive instruments are not necessary. The robust
materials used imply that the CNR4 will not suffer damages inflicted by birds.
FIGURE 6-1 and FIGURE 6-2 show the CNR4 with and without the CNF4
heater/ventilator. From a spectral point of view, the pyranometer and
pyrgeometer are complementary, and together they cover the full spectral
range.
FIGURE 6-1. The CNR4 net radiometer with cables and mounting rod,
top view
FIGURE 6-2. The CNR4 net radiometer with CNF 4 heater/ventilator
unit, top view
9
CNR4 Net Radiometer
6.1 CNR4 Specifications
Sensor sensitivities:
Operating temperature:
Operating humidity:
Bubble level sensitivity:
Sensor type:
Receiver paint:
Desiccant:
Housing material:
Shock/vibration:
CE:
Environmental protection:
Requirements for data acquisition
Radiation components:
Thermistor:
Pt-100 temperature:
Cable length:
Weight
Sensor:
Heater/ventilator, CNF4
(optional):
Mounting rod:
Four probes with unique sensitivity
values. Please refer to the calibration
sheets or label on the bottom of the
sensor for the sensitivity values.
–40 to +80°C (–40 to 176°F)
0 to 100% RH
< 0.5°
Thermopile
Carbon Black
Silica gel (replaceable)
Anodized aluminum body
IEC 721-3-2-2m2
Complies with EC guideline
89/336/EEC 73/23/EEC
IP 67
4 differential or 4 single-ended analog
channels
1 voltage excitation and 1 singleended analog channel
1 current excitation and 1 differential
analog channel.
User defined
0.85 kg (1.89 lb) without cables
0.50 kg (1.11 lb) without cables
34.7 cm (13.67 in) length
1.6 cm (0.63 in) diameter
10
6.2 Pyranometer Specifications
* indicates ISO specifications.
Spectral range:
Sensitivity:
Response time*:
Non-linearity*:
Non-stability*:
Temperature dependence of
sensitivity*:
Tilt response*:
305 to 2800 nm (50% points)
10 to 20 µV/W/m
2
< 18 seconds (95% response)
< 1% (0 to 1000 W m
-2
irradiance)
< 1%
< 4% (–10° to +40°C)
< 1% at any angle with 1000 W/m
2
CNR4 Net Radiometer
Directional error*:
Zero offset due to 0 to -200 W/m
2
IR net irradiance*:
Zero offset due to temperature
change*:
Operating temperature:
Field of view
Upper detector:
Lower detector:
Maximum solar irradiance:
Expected accuracy for daily totals:
Typical signal output for
atmospheric application:
Impedance:
Detector:
< 20 W/m
1000 W/m
< 15 W/m
< 3 W/m
< 1 W/m
2
at angle up to 80° with
2
2
2
(5 K/hr temperature change)
2
(with CNF4 installed)
–40°C to +80°C
180°
150° (due to lower solar shield to
prevent illumination at low zenith
angles)
2000 W/m
2
±10 %
0 to 15 mV
20 to 200 Ω, typically 50 Ω
Copper-constantan multi-junction
thermopile
Level accuracy:
Irradiance:
Spectral selectivity:
Uncertainty in daily total:
Instrument calibration:
6.3 Pyrgeometer Specifications
Spectral range:
Sensitivity:
Impedance:
Response time:
Non-linearity:
Temperature dependence of
sensitivity:
Tilt error:
1 degree
0 to 2000 W/m
2
< 3% (330 to 1500 nm spectral
interval)
< 5% (95% confidence level)
Indoors. Side by side against reference
CMP3 pyranometer according to ISO
9847:1992 annex A.3.1
4.5 to 42 μm (50% points)
2
5 to 15 μV/W/m
20 to 200 Ω (typically 50 Ω)
< 18 seconds (95% response)
2
< 1% (–250 to +250 W/m
irradiance)
< 4% (–10° to +40°C)
< 1% (deviation when tilted at any
angle off horizontal)
Zero offset due to temperature
change:
±4 W/m
2
(5 K/hr temperature change)
11
CNR4 Net Radiometer
Field of view
Upper:
Lower:
Net-irradiance:
Non-stability:
Window heating offset:
Uncertainty in daily total:
Typical signal output for
atmospheric application:
Temperature sensors
Thermistor:
Pt-100:
Instrument calibration:
180 degrees
150 degrees
2
–250 to +250 W/m
< 1% (sensitivity change per year)
< 6 W/m
2
(1000 W/m
2
solar
irradiance)
< 10% (95% confidence level) indoor
calibration
±5 mV
10k Ω
DIN class A
Indoors, side by side against reference
CG(R) 3 pyrgeometer. On request
outdoors, side by side against
reference CG(R) 4 pyrgeometer
6.4 Optional CNF4 Heater/Ventilator
The purpose of the heater/ventilator is to prevent dew deposition on the
pyrgeometer and pyrgeometer window, thus enhancing the measurement
accuracy and reliability. Using the heater/ventilator will have negligible effect
on the pyranometer reading.
Generally, the errors caused by the heater/ventilator will be small relative to the
errors that would have been caused by water deposition.
6.4.1 CNF4 Specifications
Heater
Power consumption:
Ventilator
Power consumption:
Supply voltage:
Weight without cable:
Operating temperature:
10 W @ 12 Vdc (15 Ω)
5 W @ 12 Vdc
8 to 13.5 Vdc
0.5 kg (1.11 lb)
–40 to +80°C
12
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