Campbell Scientific CNR4 User Manual

CNR4 Net Radiometer

Revision: 9/13

Copyright © 2000-2013

Campbell Scientific, Inc.

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customer shall assume all costs of removing, reinstalling, and shipping
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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

i

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

ii

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

iii

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

7. Operation

7.1 Using the CNR4 in the Four Separate Components Mode

7.1.1 Measuring Short-wave Solar Radiation with Pyranometer

CNR4 Net Radiometer

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. The two pyrgeometers will measure the long-wave radiation.
For proper analysis of the pyrgeometer measurement results, they must be
temperature corrected using the temperature measurement performed by the
onboard thermistor or Pt-100 sensor.

The pyranometer generates an mV signal that is simply proportional to the
incoming short-wave radiation. The conversion factor between voltage, V, and

2

of solar irradiance E, is the calibration constant C or sensitivity

W/m
(Equation 7-1).

For each pyranometer,

E = V/C (7-1)

Measuring with a pyranometer can be done by connecting two pyranometer
wires to a datalogger. Incidental light results in a positive signal. The
pyranometer mounting plate and ambient air should be at the same
temperature. Conversion of the voltage to irradiance can be done according to
Equation 7-1, and is computed by the datalogger program.

With the upward-facing pyranometer, the global (solar) downwelling radiation
is measured. The downward-facing pyranometer measures the reflected
upwelling solar radiation. When calculating the net radiation, the upwelling
radiation must be subtracted from the downwelling radiation. See Section

7.1.5, Calculation of Net Short-wave Radiation.

7.1.2 Measuring Long-wave Far Infrared Radiation with Pyrgeometer

When using the pyrgeometer, you should realize the signal generated by the
pyrgeometer represents the exchange of long-wave far infrared (thermal)
radiation between the pyrgeometer and the object that it is facing. This implies
that the pyrgeometer will generate a positive voltage output, V, when it faces
an object that is hotter than its own sensor housing, and that it will give a
negative voltage signal when it faces an object that is colder. Therefore, when
estimating the far infrared radiation that is generated by the object facing the
pyrgeometer, usually the sky or the soil, you will have to take the pyrgeometer
temperature, 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
calculation of the long-wave far infrared irradiance, E, is done according to
Equation 7-2.

13

CNR4 Net Radiometer

For the pyrgeometer only

E = V/C + 5.67•10

-8•T4

In this equation, C is the sensitivity of the sensor.

NOTE

T is in Kelvin, and not in Celsius or Fahrenheit.

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. Equation 7-2 is used to calculate the far infrared irradiance of the
sky and of the ground.

7.1.3 Measuring CNR4 Temperature with Thermistor

The CNR4 has two temperature sensors built inside: thermistor and Pt-100;
both have identical accuracy. Using the thermistor is recommended when
using Campbell Scientific dataloggers. The thermistor has a greater resistance
(10 kΩ @ 25°C) than Pt-100 sensor (100 Ω @ 0°C), and the change in
resistance with respect to temperature, in absolute terms, is greater. Therefore,
the cable resistance can be neglected, and the thermistor can easily be
measured using Half-Bridge Measurement instruction on Campbell Scientific
dataloggers.

(7-2)

TABLE 7-1 shows the thermistor resistance values as a function of
temperature.

TABLE 7-1. Resistance values versus CNR4’s thermistor temperature in °C.

Temperature

[°C]

–30
–29
–28
–27
–26
–25
–24
–23
–22
–21
–20
–19
–18
–17
–16
–15
–14

Resistance

[Ω]

135200
127900
121100
114600
108600
102900

97490
92430
87660
83160
78910
74910
71130
67570
64200
61020
58010

Temperature

[°C]

0
1
2
3
4
5
6
7
8

9
10
11
12
13
14
15
16

Resistance

[Ω]

29490
28150
26890
25690
24550
23460
22430
21450
20520
19630
18790
17980
17220
16490
15790
15130
14500

Temperature

[°C]

30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46

Resistance

[Ω]

8194
7880
7579
7291
7016
6752
6500
6258
6026
5805
5592
5389
5193
5006
4827
4655
4489

14

CNR4 Net Radiometer

TABLE 7-1. Resistance values versus CNR4’s thermistor temperature in °C.

Temperature

[°C]

–13
–12
–11
–10

–9
–8
–7
–6
–5
–4
–3
–2
–1

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. This results
in a worst case error for the pyrgeometer of 5 W/m
the largest expected deviation between the real sensor temperature and the
thermistor reading is again 1 degree. This results in a worst case error for the
pyrgeometer of 5 W/m

Resistance

[Ω]

55170
52480
49940
47540
45270
43110
41070
39140
37310
35570
33930
32370
30890

Temperature

[°C]

17
18
19
20
21
22
23
24
25
26
27
28
29

2

.

Resistance

[Ω]

13900
13330
12790
12260
11770
11290
10840
10410
10000

9605
9227
8867
8523

Temperature

[°C]

47
48
49
50
51
52
53
54
55
56
57
58
59

2

. When the sun is shining,

Resistance

[Ω]

4331
4179
4033
3893
3758
3629
3504
3385
3270
3160
3054
2952
2854

The thermistor will not give a good indication of ambient air temperature; at
1000 W/m

2

solar radiation, and no wind, the instrument temperature will rise

approximately 5 degrees above the ambient temperature.

The offsets of both the pyranometers and the pyrgeometers might be larger
than 5 W/m

2

if large temperature gradients are forced on the instrument (larger
than 5 K/hr); for example, when rain hits the instrument. This occurrence can
be detected using the thermistor readout, and can be used for data filtering.

The thermistor measurement is calculated by the datalogger, using the Half-
Bridge Measurement instruction, which requires one voltage excitation and
one single-ended analog channel.

Alternatively, you can use the Pt-100 to make the temperature measurement.
In order to make the temperature measurement, using the Pt-100 sensor, you
will need one current excitation channel, and one differential analog channel.
TABLE 7–2 shows the Pt-100 resistance values as a function of temperature.
Please refer to Appendix C, CR3000 Program for Measuring Pt-100
Temperature Sensor, for a sample program to measure Pt-100.

15

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

99.61

Temperature

[°C]

0
1
2
3
4
5
6
7
8

9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29

Resistance

[Ω]

100.00

100.39

100.78

101.17

101.56

101.95

102.34

102.73

103.12

103.51

103.90

104.29

104.68

105.07

105.46

105.85

106.24

106.63

107.02

107.40

107.79

108.18

108.57

108.96

109.35

109.73

110.12

110.51

110.90

111.28

Temperature

[°C]

30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59

Resistance

[Ω]

111.67

112.06

112.45

112.83

113.22

113.61

113.99

114.38

114.77

115.15

115.54

115.93

116.31

116.70

117.08

117.47

117.85

118.24

118.62

119.01

119.40

119.78

120.16

120.55

120.93

121.32

121.70

122.09

122.47

122.86

16

7.1.4 Calculation of Albedo

Albedo is the ratio of reflected short-wave radiation to incoming short-wave
radiation. This unitless value ranges between 0 and 1. Typical values are 0.9
for snow, and 0.3 for grassland. To determine the albedo, the measured values
of the two pyranometers are used. Do not use the measured values when the
solar elevation is lower than 10 degrees above the horizon. Errors in the
measurements at these elevations are likely and yield unreliable results. This is
due to deviations in the directional response of the pyranometers.

Albedo = (E lower Pyranometer) / (E upper Pyranometer) (7-3)

In the equation above, E is calculated according to the Equation 7-1.

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.

Net Short-wave Radiation = (E upper Pyranometer)
– (E lower Pyranometer) (7-4)

In the equation above, E is calculated according to Equation 7-1.

Net short-wave solar radiation will always be positive. This can be used as a
tool for quality assurance of your measured data.

7.1.6 Calculation of Net Long-wave Radiation

The net long-wave far infrared radiation is the part that contributes to heating
or cooling of the earth’s surface. In practice, usually the net long-wave far
infrared radiation will be negative.

CNR4 Net Radiometer

Net Long-wave Radiation = (E upper Pyrgeometer)
– (E lower Pyrgeometer) (7-5)

In the equation above, E is calculated according to Equation 7-2. According to
Equation 7-5 above, the terms that contain the sensor body temperature, T,
cancel each other. 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 upward-facing pyrgeometer) or the ground (for downward-facing
pyrgeometer). Assuming that these two, ground and sky, behave like perfect
blackbodies, theoretically, one can calculate an effective “sky temperature” and
an effective “ground temperature”.

4/1

rPyrgeometeupper E

⎡

eTemperaturSky

=

⎢
⎣

⎡

eTemperatur Ground

=

⎢
⎣

−

1067.5

⋅

1067.5

⋅

⎤

(7-6)

⎥

8

⎦

4/1

rPyrgeometelower E

⎤
⎥

8

−

⎦

(7-7)

As a rule of thumb, for ambient temperatures of about 20 degrees Celsius, one
can say that one degree of temperature difference between two objects results
in a 5 W/m

2

exchange of radiative energy (infinite objects):

1 degree of temperature difference = 5 W/m

2

(rule of thumb)

17

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:

7.2 Wiring

R
+ {(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.

The CNR4 has two outputs for short-wave radiation, two outputs for long-wave
radiation, thermistor output, and Pt-100 temperature sensor output. In addition,
if a user chooses to attach the optional CNF4 heater/ventilator unit, it will have
power wires for heater and ventilator. All wiring diagrams shown in this
manual and the sample programs will use the thermistor for the temperature
measurement of the CNR4. The wiring diagrams for the thermistor in this
manual is applicable only if the CNR4 and the cables were purchased from
Campbell Scientific, Inc.

The CNR4 comes with two sets of cables labelled SOLAR and TEMP, as
shown in FIGURE 7-1. FIGURE 7-2 shows the marks by the connecting ports
at the sensor’s end for the cable connection: S and T for SOLAR and TEMP
cables, respectively. The two cables, SOLAR and TEMP, have identical
connectors, and care should be used to ensure that the correct cables are
connected to the correct ports of the sensor.

= {(E upper Pyranometer) - (E lower Pyranometer)}

n

18

FIGURE 7-1. The CNR4 sensor with SOLAR and TEMP cables

CNR4 Net Radiometer

FIGURE 7-2. The marks on the end of the CNR4: S for SOLAR cable,

and T for TEMP cable

NOTE

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.

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

TABLE 7-3 and TABLE 7-4 show the wiring instructions for the differential
measurement and single-ended measurement connections to the datalogger,
respectively. The cables have the white band at the pigtail end of the cable
with the color keys. See FIGURE 7-3 and FIGURE 7-4 below for the labels on
the cable for both the SOLAR and TEMP cables.

FIGURE 7-3. Labels on the pigtail end of the SOLAR cable

19

CNR4 Net Radiometer

FIGURE 7-4. Labels on the pigtail end of the TEMP cable.

TABLE 7-3. Datalogger Connections for Differential Measurement

Function Wire Color CR1000 CR3000/CR5000

Pyranometer Up Signal Red Differential Input (H) Differential Input (H)

Pyranometer Up R rential Input (L) eference *Blue Differential Input (L) Diffe

Pyranometer Down Signal White Differential Input (H) Differential Input (H)

Pyranome eference Differ t (L) Dter Down R *Black ential Inpu ifferential Input (L)

Pyrgeometer Up Signal Grey Differential Input (H) Differential Input (H)

Pyrgeometer Up Reference * Yellow Differential Input (L) Differential Input (L)

Pyrgeometer Down Signal Brown Differential Input (H) Differential Input (H)

Pyrgeometer Down Reference *Green Differential Input (L) Differential Input (L)

Shield Clear

Thermistor Signal White Single-Ended Input Single-Ended Input

Thermistor Voltage Excitation Red V V oltage Excitation (VX) oltage Excitation (VX)

Thermistor Signal Reference Black

Sh ld Clear ie

*Jumper to with user supplied wire.

. Datalo onnections for Single nded Measurement TABLE 7-4 gger C -E

Function Wire Color CR1000 CR3000/CR5000

Pyranometer Up Signal Red Single-Ended Input Single-Ended Input

Pyranometer Up Reference Blue

Pyranometer Down Signal White Single-Ended Input Single-Ended Input

Pyranome eference ter Down R Black

Pyrgeometer Up Signal Grey Single-Ended Input Single-Ended Input

Pyrgeometer Up Reference Yellow

Pyrgeometer Down Signal Brown Single-Ended Input Single-Ended Input

Pyrgeometer Down Reference Green

Shield Clear

Thermistor Signal White Single-Ended Input Single-Ended Input

Thermistor Voltage Excitation Red Voltage Excitation (VX) Voltage Excitation (VX)

Thermistor Signal Reference Black

Shield Clear

*P , brown, nd yello and t

ull b (grey

ack wires for Pt-100 green, a w e,

c l tape to possible o e

able using a cable tie or electrica

avoid

), which are not in us ie P

damage to the Pt-100, due t

them around the TEM

lectrical short circuit.

20

CNR4 Net Radiometer

7.3 Datalogger Pro ming

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. The acce
measurement can be determin
ended and differential measurements made under the same conditions.

Additionally, one voltage excitation channel and one single-ended analog
channel are required to make the temperature measurement of the sensor bod
using the thermistor.

7.3.1 Sensor Sens

The CNR4 comes with four different sensor sensitivity values for four sepa
probes. The CNR4 sensor comes with two copies of its ‘Certificate of
Calibration’ by the ma
sensitivity values for four individual probes: one copy for pyranometers, and
another cop
also shown
attach the CNF4 heater/ventilator unit to the CNR4, the label showing the
serial number and sensitivity values will be covered. After attaching the
heater/ventilator, affix the extra label to the bottom of the CNF4 in a visible
location. The extra label containing the serial number and sensitivity values is
supplied with the purchase of the CNR4. Please refer to Appendix B, CNF4
Heater/Ventilator, for more details.

gram

itivity

nufacturer. They show the sensor serial number and

y for pyrgeometers. The serial number and sensitivity values are

on a label affixed to the bottom of the sensor. If you choose to

ptability of a single-ended

ed by simply comparing the results of single-

y,

rate

CNF4

7.3.2 Example Pro

7.3.2.1 Example 1, CR

2

The sensor sensitivity is in μV/(W/m

2

)/mV to be used as a multiplier parameter inside the datalogger program

(W/m
To convert the units, divide the sensor sensitivity value into 1000. For
example, if the sensitivity is 7.30 μV/(W/m

136.99 (W/m

2

)/mV.

). This needs to be converted into

2

), the multiplier is 1000/7.3 =

grams

1000 Program Using Differential Measurements

Example 1 requires fo
outputs, one excitation channel, and one single-ended channel to measure the
thermistor. T
online proce
table called cnr4_data once every 60 minutes. It also stor
data from CNR4 to data table called cnr4_ts.

Minimum battery voltage
Sample datalogger panel temperature
Average short-wave radiation (pyranometer up)
Average short-wave radiation (pyranometer down)
Average long-wave radiation (pyrge
Average long-wave radiation (pyrgeometer down)
Average CNR4 thermistor
Average CNR4 thermistor temperature
Average corrected long-wave radiation (pyrgeom
Average corrected long-wave radiation (pyrgeometer do

he program measures the sensors every 1 second, performs the

ssing of the data, and stores the following processed data to a data

ur differential channels to measure the four radiation

es the raw time-series

ometer up)

temperature (degrees C)

(Kelvin)

eter up)

wn)

.

21

CNR4 Net Radiometer

'CR1000 Series Dat logger a
'
'CNR4 program
'This program meas er ures CNR4 four-component net radiomet
'This program also NR4 measures the thermistor inside the C
'
'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.
'

'Wiring Instructions
'
'ANALOG CHANNELS
'1H CNR4 Pyranometer Upper signal (red)
'1L CNR4 Pyranometer Upper signal reference (blue)
'gnd jumper to 1L
'
'2H CNR4 Pyranometer Lower signal (white)
'2L CNR4 Pyranometer Lower signal reference (black)
'gnd jumper to 2L
'
'3H CNR4 Pyrgeometer Upper signal (grey)
'3L CNR4 Pyrgeometer Upper signal reference (yellow)
'gnd jumper to 3L
'
'4H CNR4 Pyrgeometer Lower signal (brown)
'4L CNR4 Pyrgeometer Lower signal reference (green)
'gnd jumper to 4L
' CNR4 shield (clear)
'
'
'
'8H
'8L CNR4 thermistor signal (white)
'gnd CNR4 thermistor signal reference (black)
' CNR4 thermistor shield (clear)
'

'VOLTAGE EXCITATION
'
'EX2 CNR4 thermistor voltage excitation (red)
'

'CNR4 sensor
Public logger_temp, batt_volt
Public cnr4(4)
Alias cnr4(1) = short_up
Alias cnr4(2) = short_dn
Alias cnr4(3) = long_up
Alias cnr4(4) = long_dn

Public cnr4_T_C 'CNR4 thermistor temperature in Celcius
Public cnr4_T_K 'CNR4 thermistor temperature in Kelvin
Public long_up_corr 'Downwelling long-wave radiation with temperature correction
Public long_dn_corr 'Upwelling long-wave radiation with temperature correction
Public Rs_net 'short-wave net radiation
Public Rl_net 'long-wave net radiation
Public albedo 'Albedo
Public Rn 'total net radiation

Average short-wave net radiation
Average long-wave net radiation
Average albedo
Average net radiation

22

CNR4 Net Radiometer

Units logger_temp = d gC e
Units batt_volt s = volt
Units short_up = W/m^2
Units short_dn = W/m^2
Units long_up = W/m^2
Units long_dn = W/m^2
Units cnr4_T_C = deg_C
Units cnr4_T_K = K
Units long_up_corr = W/m^2
Units long_dn_corr = W/m^2
Units Rs_net = W/m^2
Units Rl_net = W/m^2
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 'unique sensitivity for lower pyranometer
'(microV/W/m^2)
Const pyrgeometer_up_sensitivity = 8.50 'unique sensitivity for upper pyrgeometer
'(microV/W/m^2)
Const pyrgeometer_dn_sensitivity = 7.09 'unique sensitivity for lower pyrgeometer
'(microV/W/m^2)

'CNR4 multipliers
Public cnr4_mult(4)
Const pyranometer_up_mult = 1000/pyranometer_up_sensitivity '(W/m^2/mV)
Const pyranometer_dn_mult = 1000/pyranometer_dn_sensitivity '(W/m^2/mV)
Const pyrgeometer_up_mult = 1000/pyrgeometer_up_sensitivity '(W/m^2/mV)
Const pyrgeometer_dn_mult = 1000/pyrgeometer_dn_sensitivity '(W/m^2/mV)

DataTable (cnr4_data,True,-1)
DataInterval (0,60,Min,10)
CardOut (1,-1)
Minimum (1,batt_volt,FP2,0,False)
Sample (1,logger_temp,FP2)
Average (4,cnr4(1),IEEE4,False)
Average (1,cnr4_T_C,IEEE4,False)
Average (1,cnr4_T_K,IEEE4,False)
Average (1,long_up_corr,IEEE4,False)
Average (1,long_dn_corr,IEEE4,False)
Average (1,Rs_net,IEEE4,False)
Average (1,Rl_net,IEEE4,False)
Average (1,albedo,IEEE4,False)
Average (1,Rn,IEEE4,False)
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

23

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+5.67e-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_data
CallTable cnr4_ts

NextScan
EndProg

7.3. ing Differential Measurements

2.2 Example 2, CR3000 Program Us

Example 2 requires fo
outputs and one excitation
the thermistor. The progra
the online processin
data table called cn
series data from CN

ur differential channels to measure the four radiation

channel and one single-ended channel to measure

m measures the sensors every 1 second, performs

g of the data and stores the following processed data to a

r4_data once every 60 minutes. It also stores the raw time-

R4 to data table called cnr4_ts.

Minimum battery voltage
Sam
Ave
Ave
Ave
Aver

ple datalogger panel temperature
rage short-wave radiation (pyranometer up)
rage short-wave radiation (pyranometer down)
rage long-wave radiation (pyrgeometer up)

age long-wave radiation (pyrgeometer down)
Average CNR4 thermistor temperature (degrees C)
Average CNR4 thermistor temperature (Kelvin)
Average corrected long-w
Average corrected long-w
Average short-wave net ra
Average long-wave net ra

ave radiation (pyrgeometer up)
ave radiation (pyrgeometer down)

diation

diation
Average albedo
Average net radiation

24

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.
'

'Wiring Instructions
'
'ANALOG CHANNELS
'1H CNR4 Pyranometer Upper signal (red)
'1L CNR4 Pyranometer Upper signal reference (blue)
'gnd jumper to 1L
'
'2H CNR4 Pyranometer Lower signal (white)
'2L CNR4 Pyranometer Lower signal reference (black)
'gnd jumnper to 2L
'
'3H CNR4 Pyrgeometer Upper signal (grey)
'3L CNR4 Pyrgeometer Upper signal reference (yellow)
'gnd jumper to 3L
'
'4H CNR4 Pyrgeometer Lower signal (brown)
'4L CNR4 Pyrgeometer Lower signal reference (green)
'gnd jumper to 4L
' CNR4 shield (clear)
'
'
'8H
'8L CNR4 thermistor signal (white)
'gnd CNR4 thermistor signal reference (black)
' CNR4 thermistor shield (clear)
'

'VOLTAGE EXCITATION
'
'VX1 CNR4 thermistor voltage excitation (red)
'

'CNR4 sensor
Public logger_temp, batt_volt
Public cnr4(4)
Alias cnr4(1) = short_up
Alias cnr4(2) = short_dn
Alias cnr4(3) = long_up
Alias cnr4(4) = lo g_dn n

Public cnr4_T_C 'CNR ius 4 thermistor temperature in Celc
Public cnr4_T_K 'CNR4 thermistor temperature in Kelvin
Public long_up_cor 'Dow re correction r nwelling long-wave radiation with temperatu
Public long_dn_cor 'Upw ection r elling long-wave radiation with temperature corr
Public Rs_net 'short-wave net radiation
Public Rl_net 'long-wave net radiation
Public albedo 'Albedo
Public Rn 'total net radiation

Units logger_temp degC =
Units batt_volt = olts v
Units short_up = W m^2 /
Units short_dn = W m^2 /
Units long_up = W/m^2
Units long_dn = W/m^2
Units cnr4_T_C = deg_C
Units cnr4_T_K = K

25

CNR4 Net Radiometer

Units long_up_corr = W/m^2
Units long_dn_corr = W/m^2
Units Rs_net = W/m^2
Units Rl_net = W/m^2
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 'unique sensitivity for lower pyranometer
'(microV/W/m^2)
Const pyrgeometer_up_sensitivity = 8.50 'unique sensitivity for upper pyrgeometer
'(microV/W/m^2)
Const pyrgeometer_dn_sensitivity = 7.09 'unique sensitivity for lower pyrgeometer
'(microV/W/m^2)

'CNR4 multipliers
Public cnr4_mult(4)
Const pyranometer_up_mult = 1000/pyranometer_up_sensitivity '(W/m^2/mV)
Const pyranometer_dn_mult = 1000/pyranometer_dn_sensitivity '(W/m^2/mV)
Const pyrgeometer_up_mult = 1000/pyrgeometer_up_sensitivity '(W/m^2/mV)
Const pyrgeometer_dn_mult = 1000/pyrgeometer_dn_sensitivity '(W/m^2/mV)

DataTable (cnr4_data,True,-1)
DataInterval (0,60,Min,10)
CardOut (1,-1)
Minimum (1,batt_volt,FP2,0,False)
Sample (1,logger_temp,FP2)
Average (4,cnr4(1),IEEE4,False)
Average (1,cnr4_T_C,IEEE4,False)
Average (1,cnr4_T_K,IEEE4,False)
Average (1,long_up_corr,IEEE4,False)
Average (1,long_dn_corr,IEEE4,False)
Average (1,Rs_net,IEEE4,False)
Average (1,Rl_net,IEEE4,False)
Average (1,albedo,IEEE4,False)
Average (1,Rn,IEEE4,False)
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 multiplie alues for the CNR4 r v
cnr4_mu 1) = pyranometer_up_mult lt(
cnr4_mult 2) = pyranometer_dn_mult (
cnr4_mult 3) = pyrgeometer_up_mult (
cnr 4) = pyrgeometer_dn_mult 4_mult(

Scan (1,Sec,3,0)
PanelTe temp,250) mp (logger_
Battery (batt_volt)

'CNR4 radiation measurements
VoltDiff (cnr4(),4,mV20C,1,True ,0,_60Hz,cnr4_mult(),0)

26

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+5.67e-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_data
CallTable cnr4_ts

NextScan
EndProg

7.3. m Using Differential Measurements

2.3 Example 3, CR5000 Progra

ur differential channels to measure the four radiation

n channel, and one single-ended channel to measure the

easures the sensors every 1 second, performs the
a, and stores the following processed data to a data

ta once every 60 minutes. It also stores the raw time-series

data table called cnr4_ts.

NOTE

Example 3 requires fo
outputs, one excitatio
thermistor. The program m
online processing of the dat
table called cnr4_da
data from CNR4 to

The variables for the CR5000 datalogger can be up to 16
characters in length. However, if the variable is processed in the
output table by an
be truncate
underscore a

output type other than Sample, the name will

d in the datalogger to 12 characters, plus an

nd a 3 digit suffix indicating the output type (for

example, _avg, _max).

Minimum battery voltage
Sample datalogger panel temperature
Average short-wave radia
Average short-wave radia

Average

Average long-wave radiation (pyrgeometer up)

long-wave radiation (pyrgeometer down)

Average CNR4 thermistor temperature (degrees C)

tion (pyranometer up)
tion (pyranometer down)

Average CNR4 thermistor temperature (Kelvin)
Average corrected long-wave radiation (pyrgeometer up)
Average corrected long-wave radiation (pyrgeometer dow
Average short-wave net radiation
Average long-wave net radiation
Average albedo
Average net radiation

n)

27

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.
'

'Wiring Instructions
'
'ANALOG CHANNELS
'1H CNR4 Pyranometer Upper signal (red)
'1L CNR4 Pyranometer Upper signal reference (blue)
'gnd jumper to 1L
'
'2H CNR4 Pyranometer Lower signal (white)
'2L CNR4 Pyranometer Lower signal reference (black)
'gnd jumnper to 2L
'
'3H CNR4 Pyrgeometer Upper signal (grey)
'3L CNR4 Pyrgeometer Upper signal reference (yellow)
'gnd jumper to 3L
'
'4H CNR4 Pyrgeometer Lower signal (brown)
'4L CNR4 Pyrgeometer Lower signal reference (green)
'gnd jumper to L 4
' CNR4 shield (clear)
'
'
'8H
'8L CNR4 thermistor signal (white)
'gnd CNR4 thermistor signal reference (black)
' CNR4 thermistor shield (clear)
'

'VOLTAGE EXCITATION
'
'VX1 CNR4 thermistor voltage excitation (red)
'

'CNR4 sensor
Public logger_temp, batt_volt
Public cnr4(4)
Alias cnr4(1) = short_up
Alias cnr4(2) = short_dn
Alias cnr4(3) = long_up
Alias cnr4(4) = long_dn

Public cnr4_T_C 'CNR ius 4 thermistor temperature in Celc
Public cnr4_T_K 'CNR4 thermistor temperature in Kelvin
Public long_up_cor 'Dow e correction r nwelling long-wave radiation with temperatur
Public long_dn_cor 'Upw correction r elling long-wave radiation with temperature
Public Rs_net 'short-wave net radiation
Public Rl_net 'long-wave net radiation
Public albedo 'Albedo
Public Rn 'total net radiation

Units logger_temp degC =
Units batt_volt = olts v
Units short_up = W m^2 /
Units short_dn = W m^2 /
Units long_up = W/m^2
Units long_dn = W/m^2
Units cnr4_T_C = deg_C

28

CNR4 Net Radiometer

Units cnr4_T_K = K
Units long_up_corr = W/m^2
Units long_dn_corr = W/m^2
Units Rs_net = W/m^2
Units Rl_net = W/m^2
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 'unique sensitivity for lower pyranometer (microV/W/m^2)
Const pyrg_up_sensitiv = 8.50 'unique sensitivity for upper pyrgeometer (microV/W/m^2)
Const pyrg_dn_sensitiv = 7.09 'unique sensitivity for lower pyrgeometer (microV/W/m^2)

'CNR4 multipliers
Public cnr4_mult(4)
Const pyra_up_mult = 1000/pyra_up_sensitiv '(W/m^2/mV)
Const pyra_dn_mult = 1000/pyra_dn_sensitiv '(W/m^2/mV)
Const pyrg_up_mult = 1000/pyrg_up_sensitiv '(W/m^2/mV)
Const pyrg_dn_mult = 1000/pyrg_dn_sensitiv '(W/m^2/mV)

DataTable (cnr4_dat,True,-1)
DataInterval (0,60,Min,10)
CardOut (1,-1)
Minimum (1,batt_volt,FP2,0,False)
Sample (1,logger_temp,FP2)
Average (4,cnr4(1),IEEE4,False)
Average (1,cnr4_T_C,IEEE4,False)
Average (1,cnr4_T_K,IEEE4,False)
Average (1,long_up_corr,IEEE4,False)
Average (1,long_dn_corr,IEEE4,False)
Average (1,Rs_net,IEEE4,False)
Average (1,Rl_net,IEEE4,False)
Average (1,albedo,IEEE4,False)
Average (1,Rn,IEEE4,False)
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_mu 4) = pyrg_dn_mult lt(

Scan (1,Sec,3,0)
PanelTemp (logger_temp,250)
Battery (ba ) tt_volt

'CNR4 radiation ements measur
Volt (),4,mV20C,1,True ,0,_60Diff (cnr4 Hz,cnr4_mult(),0)

'CNR4 thermistor measurement
BrHalf (Vs_Vx,1,mv5000,21,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

29

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. Tr

8.1

oubleshooting

If there is no indicatio
following “upside-down te
be performed both outdoor
source for both short­preferably work wi
above horizon) and
irradiance, and prefe

1. Measur

measure

e the radiation outputs in the normal position. Record the

d values when the signals have stabilized, i.e. after about three

minutes.

2. Rotate t

he instrument 180 degrees, so that the upper and the lower sensors

are now in the reverse orientation as to the previous position.

3. Measure the radiation out

when the radiometers

4. The computed net rad

magnitude but only differing in sign. In a rough test like this, deviations
of ± 10 % can be tolerated. If deviations greater than this are encountered,
additional tes

Testing the Pyranometer

wave and long-wave radiation. Outdoors, one should
th a solar elevation of more than 45 degrees (45 degrees
under stable conditions (no large changes in solar

rably no clouds).

ting is warranted.

n as to what may be the problem, start performing the

st”, which is a rough test for a first diagnosis. It can
s and indoors. Indoors, a lamp can be used as a

puts once more. Record the measured values

have stabilized.

iation values in rotated position should be equal in

30

As a first test,
indicated in the specifications. Zero, or infinite resistan

check the sensor impedance. It should have a nominal value as

ce, indicates a failure in

hardware connection.

Before starting the second test measurement, let the pyranometer rest for at
least five minutes to let it regain its thermal equilibrium. For testing, set a

CNR4 Net Radiometer

voltmeter to its most sensitive range setting. Darken the sensor. The signal
should read zero; this response ca
from zero are possible; this is caused by the therm
the pyranometer with your hand. This thermal effe
deliberately heating the pyranometer with your hand. If
within specifications, proceed with the third test.

n take up to one minute. Small deviations

al effects, such as touching

ct can be demonstrated by

the zero offset is

In the third test, the sensor sho
positive reading. S
scale output of the pyranome
voltmeter. The range can be estimated on theoretical considerations. When the
maximum expected radiation is 1500
outdoor daylight conditions

2

, the e

W/m

22.5 mV. One can calculate the radiation intensity by dividing the
pyra ut as m the voltmeter ex ) nom

your

eter outp easured by (for ample, 22.5 mV by

sor sensitivity (15 μV/W/m

nthe se

pyranometer is probably operating correctly.

et the voltmeter range in such a way that the expected full-

xpected output range of the pyranometer is equal to 22500 μV, or

8.2 Testing the Pyrgeometer

It is assumed that the zero offset is no more than a few watts per square meter
(see second tes

The CNR4 body and the ambient air should be at the same temperature. 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, put your hand in front of the pyrgeometer. The thermal
radiation from your hand will cause the pyrgeometer to generate a positive
voltage when the surface temperature of your hand is higher than the
pyrgeometer temperature. The pyrgeometer will generate a negative vo
the hand is colder. The signal is proportiona
the rule of thumb in Section 7.1.6, Calculation of Net Long-wave Radia
The

radiation emitted by the hand can be calculated by dividing the

pyrg tput by the sensor’s sensitivity value, and subsequently

eometer ou

correcting for the temperature, according to Equation 5-2. If there are still no

lt

fau s found, your pyrgeometer is probably operating correctly.

t in Section 8.1, Testing the Pyranometer).

uld be exposed to light. The signal should be a

ter is within the full-scale input range of the

2

, which is roughly equal to normal

W/m

, and the sensitivity of the pyranometer is 15 μV per

2

). If no faults are found up to this point,

ltage if

l to the temperature difference (see

tion).

8.3 Testing th

e Thermistor

Usin between the black and white wires

g a multimeter, measure the resistance

h

of t e thermistor, and compare the value with the resistance values listed in
TAB

LE 7-1. The resistance should be around 10 k Ω at 25 °C, and the cable

resist

ance should add about 0.026 Ω per each foot of cable. When in doubt, the

Pt-1 e checked as well for reference.

00 resistance (temperature) can b

8.4 Testing the Pt-100

Using a multimeter, measure the resistance between the two opposite wires of
the Pt-100 (gray-yellow, gray-brown, green-yellow, green-brown), and
compare the measured
The resistance should be above 100 Ω at 0°C, and the cable resistance should
add about 0.026 Ω per each foot of cable. When in doub,t the thermistor
resistance (temperature) can be checked as well for reference.

value with the resistance values listed in TABLE 7–2.

31

CNR4 Net Radiometer

9. Maintenance

9.1 Cleaning W

9.2 Recalibrat

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 take

indows 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. Use distilled water or alcohol as cleaning solution,
being careful not to scratch the windows and domes during cleaning.

ion

For quality assurance of the measured data, the manufacturer recommends th
CNR4 be recalibrated on a regular schedule by an a
calibration facility.

The CNR4 should be reca
check the sensor calibration by letting a higher standard run parallel to it over a
two-day period and, then, comparing the results. For comparison of
pyranometers, one should use a clear day. For comparison
one should compare the nighttime results. If the deviations are greater than
6%, the sensor should be recalibrated.

librated every two years. Alternatively, one can

uthorized Kipp & Zonen

of pyrgeometers,

n.

e

9.3 Replacing

Please contact Campbell Scientific to obtain an RMA number for recalibration.

the Drying Cartridge

The CNR4 has a drying cartridge inside the sensor to help keep the electronics
dry. The manufacturer recommends replacing the drying cartridge every 6 to
12 months. The three screws holding the white solar shield and the six
holding the aluminium base plate need to be removed to access the drying
cartridge, as shown in FIGURE 9-1. Make sure that the black rubber gasket is
put in place properly before the base plate is put back to keep the
sealed. The CNR4 comes with two spare drying cartridges. Additional drying
cartridges, pn 26006, c

an be purchased from Campbell Scientific.

screws

compartment

32

t

Drying Cartridge

Rubber Gaske

FIGURE 9-1. Replacing the drying cartridge

CNR4 Net Radiometer

9.4 Replaceme

nt Parts

The following is the list of replacement
(heater/ventilator) available from Campbell Scientific.

CSI Part
Number

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).

Description

See Appendix B, CNF4 Heater/Ventilator, for fan filter
replacement instruction.

parts for the CNR4 and CNF4

33

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. The third parameter is ambient temperature; this is included to
show that the sky temperature, column nine, “sky T”, tracks the ambient
temperature. Under cloudy conditions this is logical; cloud bases will be colder
than the ambient temperature. At instrument level, the temperature difference
depends roughly on cloud altitude.

Under clear sky conditions, it is less obvious that sky temperature “adjusts” to
the ambient temperature. This can roughly be attributed to the water vapor 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.

1 2 3 4 5 6 7 8 9 10

Day

night

* Values may suffer from the so-called window heating offset; the sun heats the pyrgeometer window causing a
measurement error of +10 Watts per square meter (maximum).

Cloudy

clear

d cloud [phone] 20 20

d cloud –20 0 0 0–500 0–150 –20 –20 –20

d clear +20 –100* 0 0–1300 0–400 20 1* 20

d clear –20 –100* 0 0–1300 0–400 –20 –53* –20

n cloud [phone]

n cloud –20 0 0 0 0 –20 –20 –20

n clear +20 –100*** 0 0** 0 20 1*** 20

n clear –20 –100*** 0 0** 0 –20 –53*** –20

+20ºC
–20ºC

Pyrgeo–

meter

Up

Pyrgeo–

meter

low

Pyrano–

meter

up

Pyrano–

meter

low

Pt

100

sky T

ground

T

** Values may suffer from negative infrared offsets, caused by cooling off of the pyranometer dome by far
infrared radiation. The maximum expected offset value is 15 Watts per square meter.

*** Values may suffer from dew deposition. This causes the pyrgeometer-up values to rise from –100 to 0 Watts
per square meter.

A-1

‐10

‐20

‐30

Appendix A. CNR4 Performance and Measurements under Different Conditions

Upwelling Signal (Downward Facing) Pyrgeometer

upwellingsignal(downwardfacing)pyrgeometer

30

Pyrgeometer:U‐emf/sensitivity[W/m²] Tempofinstrument[°C]

20

10

0

0:00:00

1:00:00

2:00:00

3:00:00

4:00:00

5:00:00

6:00:00

7:00:00

8:00:00

9:00:00

10:00:00

11:00:00

12:00:00

13:00:00

14:00:00

15:00:00

16:00:00

17:00:00

18:00:00

19:00:00

20:00:00

21:00:00

22:00

23:00:

0:00:

:00

00

00

FI rd facing pyrgeometer

GURE A-3. Clear day for the downwa

It is ass d th bi he ne nfr
radi
resu
colu
st
with sor ture. Th dicated in co umn ring y,
t
am
than
two e
gro hey are n n into ac t in th ble. In mn 4,
one
co
t is co der cond s, this
temp
temp

ume at when am ent temperature varies, t t far i ared

ation roug me, in t of ambient temperature. The

remains

lting d val yrg and p ome sho

measure

mns 4 TABL hese cative res only, they depend

to 7 in

rongly on r circumstances; the pyr eter results, of course, change

othe

hly the sa
ues of the p

E A-1. T

dependen

eometers

are indi

geom

yran

figu

ters are wn in

the sen tempera is is in l 8. Du the da

he Pt-100 r ing may o sola g, up degr ove

bient tem rature. D e night or t atur be low

the am pe e to fa d radi oli e lat

ead

pe

bient temorature du

ffects d not influence nd res e calcul ions of T and

rise due t

uring th

the e

r heatin
, the sens

r infrare

ult of th

to 10
emper

ees ab

e may er

ative coatng. Th

sky

und T. Therefore, t ot take coun e ta colu

might e to see “0 –50” for all sitions t showing “0”; i

lumn 5, th ” values m reality b -20 to +2 The r g sky

xpect

e “0

to

ay in

po

e “

hat are

0”.

emperature indicated in lumn 9. Un cloudy ition sky

erature equal to a t temperatu . Under clear con , the s

is

erature lower than mbient tem rature.

is

mbien

the a

re
pe

ditions ky

ter

n

esultin

The ground temperature, in column 10, is assumed to be equal to the ambient
temperature. In practice, it may be higher during the day, due to solar heating.
Ground temperature may be lower than ambient during the night, due to far
infrared radiative cooling. The sky and the ground temperature can be
calculated from the measured

values of the sensors using formulas A-1 and A-2

below.

A-3

Appendix A. CNR4 Performance and Measurements under Different Conditions

⎡

=

(A-1)

eTemperaturSky

⎢
⎣

⎡

eTemperatur Ground

=

⎢
⎣

CG3upper E

−

⋅

1067.5

1067.5

⋅

4/1

⎤
⎥

8

⎦

CG3lower E

4/1

⎤
⎥

−

8

⎦

(A-2)

A-4

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. Heating
the sensor disturbs this equilibrium. The heating causes the zero offset error on
the pyranometer (10 W/m
the sensor (2 degree typical). Therefore, the heater should be used only if
absolutely necessary. The pyrgeometer is less sensitive to this. Offset values
for the pyrgeometer cannot be determined, and, therefore, are not specified.

B.1 General Information

The primary reason for heating the sensor is to avoid the water deposition on
the pyrgeometer sensor window and on the pyranometer domes. The water
deposition on the pyrgeometer window will ultimately obstruct the far infrared
radiation completely. During a rain event, this will probably not lead to
significant errors, because with an overcast sky, the signal is close to z
anyway. However, the dew deposition is far more significant. Dew deposition
will probably take place under conditions with large far infrared irradiation
from the pyrgeometer to the clear sky, typically –100 W/m
windows of pyrgeometer can cause the –100 W/m
a case, the heater should be used because the error described above is
significantly smaller than the gain obtained by heating the sensor to avoid the
dew deposition.

2

typical), and the temperature measurement error on

ero

2.

2

signal to go to zero. In such

The dew on the

Please refer to the following diagram to determine whether or not the heater
should be used.

B-1

Appendix B. CNF4 Heater/Ventilator Appendix B. CNF4 Heater/Ventilator

10 watt power available?

10 watt power available?

Clock and relay available?

Clock and relay available?

Not available

Not available

DO NOT HEAT

DO NOT HEAT

Available Consider op

Available Consider options below tions below

Not Available

Not Available

DO NOT

DO NOT HEAT

(recommendation)

Available

Heat from 1 hour before sunset until

1 hour after sunrise.

CAUTION

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. Connect the power ground from the heater to a G terminal close to
the SW12V channel of the datalogger (not to an analog ground near the
measurement inputs).

The heater power can be controlled by the datalogger program. For example,
the datalogger program can turn on the heater only when the light level falls
below 20 W/m

2

or, if a measurement of air humidity is available, when the dew

point of the air falls to within 1ºC of the sensor body temperature.

Do not use the SW12 channel of a CR1000 or CR3000 to
simultaneously power the heater and ventilator.
Simultaneously powering the heater and ventilator will
exceed the current limit of the SW12 channel. If the heater
and ventilator need to be used at the same time, connect
the CNF4 to the 12V channel instead of the SW12 channel
and use an external relay to switch the power on and off.
Refer to Section 4.2 of the CR1000 and CR3000 manual
for details on the 12V current source limits.

B-2

B-2

Appendix B. CNF4 Heater/Ventilator

B.2 Attaching the Optional CNF4 Heater/Ventilato

Unit to CNR4

1. The CNF4 heater/ventilator unit comes with the following: the

heater/ventilator, the white solar shield, three pan-head screws
washers, and four flat-head screws as shown in FIGURE B-1.

with

r

FIGURE B-1. CNF4 package contents

B-3

Appendix B. CNF4 Heater/Ventilator

2. Attach the heater/ventilator unit unto the bottom of the CNR4 sensor,

using the t ws and washers, as shown in FIGURE B-2.
Make sure that the pyranometer and the pyrgeometer windows are not
scratched during the installation.

hree pan-head scre

FIGURE B-2. Attaching the CNF4 to CNR4 using pan-head screws and

washers

B-4

Appendix B. CNF4 Heater/Ventilator

3. Make sure the cables are cleared from the edges of the CNF4, as show

FIGURE B-3, and place the white solar shield over it. Use the four fl
h

ead screws provided to complete the solar shield installation to the CNF4,

as show

n in FIGURE B-4 and FIGURE B-5.

n in

at-

FIGURE B-3. Making sure the cables are clear from the edges

FIGURE B-4. CNF4 solar shield and four flat-head screws

B-5

Appendix B. CNF4 Heater/Ventilator

FIGURE B-5. Attaching the solar shield to CNF4 using four flat-head

4. Once the CNF4 heater/ventilator unit is attached to the bottom side of the

screws

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.

B-6

FIGURE B-6. Affixing the sensor label to CNF4

5. Connect the heater/ventilator power control cable and the mounting rod to

the CNF4, as shown in FIGURE B-7.

FIGURE B-7. Connecting the CNF4 power control cable and the

mounting rod

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 m
measurement.

TABLE B-1. CR1000 and CR3000 Datalogger Connections for Differential Measurement with

Heater/Ventilator Control

Function Wire Color CR1000 CR3000

Pyranometer Up Signal Red Differential Input (H) Differential Input (H)

Pyranometer Up Reference *Blue Differential Input (L) Differential Input (L)

Pyranometer Down Signal White Differential Input (H) Differential Input (H)

Pyranometer Down Reference *Black Differential Input (L) Differential Input (L)

Pyrgeometer Up Signal Grey Differential Input (H) Differential Input (H)

Pyrgeometer Up Reference *Yellow Differential Input (L) Differential Input (L)

Pyrgeometer Down Signal Brown Differential Input (H) Differential Input (H)

Pyrgeometer Down Reference *Green Differential Input (L) Differential Input (L)

Shield Clear

Thermistor

Thermistor Signal White Single-Ended Input Single-Ended Input

Thermistor Voltage Excitation Red Voltage Excitation (VX) Voltage Excitatio (VX) n

Thermistor Signal Reference Black

Shield Clear

CNF4 Heater/Ventilator

Ventilator Power Red SW12V SW12V-1

Ventilator Ground Blue G G

Heater Power Green SW12V SW12V-2

Heater Ground Yellow G G

Shield Clear

*Jumper to with user supplied wire

aking the differential

Pull back wires for Pt-100 (grey, brown, green, and yellow), which are not in use, and tie them around the TEMP
cable using a cable tie or electrical tape to avoid possible damage to the Pt-100, due to electrical short circuit.

CAUTION

Do not use the SW12 channel of a CR1000 or CR3000 to
simultaneously power the heater and ventilator.
Simultaneously powering the heater and ventilator will
exceed the current limit of the SW12 channel. If the heater
and ventilator need to be used at the same time, connect
the CNF4 to the 12V channel instead of the SW12 channel
and use an external relay to switch the power on and off.
Refer to Section 4.1 of the CR1000 and CR3000 manual
for details on the 12V current source limits.

B-7

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. The program can be modified to include the conditional
statements to control the heater and ventilator based upon the environmental
parameters, such as light level and dew point temperature.

CAUTION

Do not use the SW12 channel of a CR1000 or CR3000 to
simultaneously power the heater and ventilator.
Simultaneously powering the heater and ventilator will
exceed the current limit of the SW12 channel. If the heate
and ventilator need to be used at the same time, connec

r

t
the CNF4 to the 12V channel instead of the SW12 channel
and use an external relay to switch the power on and off.
Ref tion 4.1 of the CR1000 and CR3000 manual

er to Sec

for details on the 12V current source limits.

'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.
'
'
'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.
'

'Wiring Instructions
'
'ANALOG CHANNELS
'1H CNR4 Pyranometer Upper signal (red)
'1L CNR4 Pyranometer Upper signal reference (blue)
'gnd jumper to 1L
'
'2H CNR4 Pyranometer Lower signal (white)
'2L CNR4 Pyranometer Lower signal reference (thin black)
'gnd jumper to 2L
'
'3H CNR4 Pyrgeometer Upper signal (grey)
'3L CNR4 Pyrgeometer Upper signal reference (yellow)
'gnd jumper to 3L
'
'4H CNR4 Pyrgeometer Lower signal (brown)
'4L CNR4 Pyrgeometer Lower signal reference (green)
'gnd jumper to 4L
' CNR4 shield (clear)
'
'

B-8

Appendix B. CNF4 Heater/Ventilator

'8H
'8L CNR4 thermistor signal (white)
'gnd CNR4 thermistor signal reference (black)
' CNR4 thermistor shield (clear)
'

'VOLTAGE EXCITATION
'
'VX1 CNR4 thermistor voltage excitation (red)
'

'POWER OUT
'SW12V-1 CNF4 vent d) ilator + (re
'
'SW12V-2 CNF4 heater een) + (gr
'
'G CNF4 lator - venti (blue)
' CN ter - (yF4 hea ellow)
'
'gnd ventilator & he hield (cater s lear)

PipeLineMode

'CNR4 sensor
Public logger_temp, batt_volt
Public flag(2) As Boolean
Public cnr4(4)
Alias cnr4(1) = short_up
Alias cnr4(2) = short_dn
Alias cnr4(3) = long_up
Alias cnr4(4) = long_dn

Public cnr4_T_C 'CNR thermistor tempe Celcius 4 ra re intu
Public cnr4_T_K 'C hermistor temp in Kelvin NR4 t erature
Public long_up_corr 'D lling long-wave iation with temperature correction ownwe rad
Public long_dn_corr ' long-wave n with temperaturUpwelling radiatio e correction
Public Rs_net ' ave net radiashort-w tion
Public Rl_net ' ve net radiatiolong-wa n
Public albedo ' Albedo
P 'total net radiation ublic Rn

Units logger_temp = degC
Units batt_volt = volts
Units short_up = W/m^2
Units short_dn = W/m^2
Unit W/ms long_up = ^2
Uni = W/ts long_dn m^2
Units cnr4_T_C = deg_C
Units cnr4_T_K = K
Units long_up_corr = W/m^2
Units long_dn_corr = W/m^2
Units Rs_net = W/m^2
Units Rl_net = W/m^2
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 'unique sensitivity for lower pyranometer
'(microV/W/m^2)
Const pyrgeometer_up_sensitivity = 8.50 'unique sensitivity for upper pyrgeometer
'(microV/W/m^2)
Const pyrgeometer_dn_sensitivity = 7.09 'unique sensitivity for lower pyrgeometer
'(microV/W/m^2)

B-9

Appendix B. CNF4 Heater/Ventilator

'CNR4 multipliers
Public cnr4_mult(4)
Const pyranometer_up_mult = 1000/pyranometer_up_sensitivity '(W/m^2/mV)
Const pyranometer_dn_mult = 1000/pyranometer_dn_sensitivity '(W/m^2/mV)
Const pyrgeometer_up_mult = 1000/pyrgeometer_up_sensitivity '(W/m^2/mV)
Const pyrgeometer_dn_mult = 1000/pyrgeometer_dn_sensitivity '(W/m^2/mV)

DataTable (cnr4_data,True,-1)
DataInterval (0,60,Min,10)
CardOut (1,-1)
Minimum (1,batt_volt,FP2,0,False)
Sample (1,logger_temp,FP2)
Average (4,cnr4(1),IEEE4,False)
Average (1,cnr4_T_C,IEEE4,False)
A nr4_verage (1,c T_K,IEEE4,False)
A ong_verage (1,l up_corr,IEEE4,False)
Average (1,long_dn_corr,IEEE4,False)
Average (1,Rs_net,IEEE4,False)
Average (1,Rl_net,IEEE4,False)
Average (1,albedo,IEEE4,False)
Average (1,Rn,IEEE4,False)
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
VoltDiff (cnr4(),4,mV20C,1,True ,0,_60Hz,cnr4_mult(),0)

'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+5.67e-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

B-10

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 g the Heater

.1 Testin

The optional C
unit, measure t
The resist
resistanc
resistanc

B.5

.2 Testing the Ventilator

c

To heck the ventilator, first measure the impedance of the ventilator motor.
The value should be around 30 Ω (cable resistance should add about 0.026 Ω
per e resistance value is measured, but the

ach foot of cable). If the correct

vent ossible that the ventilator is stalled by an

ilator still mal-functions, it is p

obje ve the black cover at the bottom side of the

ct blocking the fan. Remo
ventilator unit, by prying it open with a small flat-head screw driver or by
pulling it
the fan’
back in

place.

B.5 Filter for the Ventilator

.3 Replacing the

The filter n
cover at the

screw driver or by pulling it straight out. Inspect the filter for dust and

head

icles that might impede the air flow into the ventilator. The filter can be

part
cleaned with warm clean water, or can be replaced with the new one. You can
purchase the replacement filters, pn 26010, from Campbell Scientific.

NF4 consists of a heater and a ventilator. To check the heater

he resistance between the two heater wires (green and yellow).

ance value of the heating resistor inside should be around 15 Ω (cable

e should add about 0.026 Ω per each foot of cable). An infinite
e reading indicates the likelihood of a broken wire, or cable.

straight out. Inspect the fan inside for any object that might impede

s rotation. Upon completing the inspection, put the filter and the cover

eeds to be checked for every 6 to 12 months. Remove the black

bottom side of the ventilator by prying it open with a small flat-

B-11

Appendix B. CNF4 Heater/Ventilator

B-12

Appe gram for

ndix C. CR3000 Pro

Measuring Pt-100 Temperature Sensor

Example C measures the Pt-100 senso te perature of the C R4.

gram requ s four different measure the four radi ion

ts, one current excitation channel, and one differential channel for Pt-100

outpu
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 c

ata from CNR4 to data table called cnr4_ts.

d

Minimum battery voltage
Sample datalogger panel temperature
Average short-wave radiation (pyranometer up)
Averag
Averag
Average long-wave radiation (pyrgeometer down)
Average CNR4 thermistor temperature (degrees C)
Average CNR4 thermistor temperature (Kelvin)
Average corrected long-wave radiation (pyrgeometer up)
Average corrected long-wave radiation (pyrgeometer down)
Average short-wave net radiation
Average lon
Average albe
Average net radiation

ire ial channels to atThis pro

nr4_data once every 60 minutes. It also stores the raw time-series

e short-wave radiation (pyranometer down)
e long-wave radiation (pyrgeometer up)

g-wave net radiation

do

r for the body m N

TABLE C-1. Datal

Function Wire Color CR3000/CR5000

Pyranometer Up Signal Red Differential Input (H)

Pyranometer Up Reference *Blue Differential Input (L)

Pyranometer Down Signal White Differential Input (H)

Pyranometer Down Refere *Black Differential Input (L) nce

Pyrgeometer Up Signal Grey Differential Input (H)

Pyrgeom ter Up Reference *Yellow De ifferential Input (L)

Pyrgeom ter Down Signal Brown De ifferential Input (H)

Pyrgeometer Down Reference *Green Differential Input (L)

Shield Clear

PRT (Pt-100) Current Excitation Grey Current Excitation (IX)

PRT (Pt-100) Current Return Brown Current Excitation Return (IXR)

PRT (Pt-100) Signal Green Differential Input (H)

PRT (Pt-100) Signal Reference Yellow Differential Input (L)

Shield Clear

*Pull back wires for thermistor (white, red, and black), which are not in use, and tie them around the TEMP cable
using a cable tie or electrical tape t oid possible damage to the thermistor, due to electrical short circuit. o av

ogger Connections for Differential Measurement with Pt-100

C-1

Appendix C. CR3000 Program for Measuring Pt-100 Temperature Sensor

'CR3000 Series Dat logger a
'
'CNR4 program
'This program meas res CNR4 four-component net radiometer u
'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 download ng it to the datalogger. i
'Search for the text string "unique" to find places to enter the sensitivity values.
'

'Wiring Instructions
'
'ANALOG CHANNELS
'1H CNR4 Pyranometer Upper signal (red)
'1L CNR4 Pyranometer Upper signal reference (blue)
'gnd jumper to 1L
'
'2H CNR4 Pyranometer Lower signal (white)
'2L CNR4 Pyranometer Lower signal reference (thin black)
'gnd jumnper to 2L
'
'3H CNR4 Pyrgeometer Upper signal (grey)
'3L CNR4 Pyrgeometer Upper signal reference (yellow)
'gnd jumper to 3L
'
'4H CNR4 Pyrgeometer Lower signal (brown)
'4L CNR4 Pyrgeometer Lower signal reference (green)
'gnd jumper to 4L
' CNR4 shield (clear)
'
'
'8H CNR4 PRT (Pt-100) signal (green)
'8L CNR4 PRT (Pt-100) signal reference (yellow)
'gnd CNR4 PRT (Pt-100) shield (clear)
'

'CURRENT EXCITATION
'IX1 CNR4 PRT (Pt-100) current excitation (grey)
'
'IXR CNR4 PRT (Pt-100) current excitation return (brown)
'

'CNR4 sensor
Public logger_temp, batt_volt
Public cnr4(4)
Alias cnr4(1) = short_up
Alias cnr4(2) = short_dn
Alias cnr4(3) = long_up
Alias cnr4(4) = long_dn

Public cnr4_T_C 'CNR4 thermistor temperature in Celcius
Public cnr4_T_K 'CNR4 thermistor temperature in Kelvin
Public long_up_corr 'Downwelling long-wave radiation with temperature correction
Public long_dn_corr 'Upwelling long-wave radiation with temperature correction
Public Rs_net 'short-wave net radiation
Public Rl_net 'long-wave net radiation
Public albedo 'Albedo
Public Rn 'total net radiation

Units logger_temp = degC
Units batt_volt = volts
Units short_up = W/m^2
Units short_dn = W/m^2
Units long_up = W/m^2
Units long_dn = W/m^2
Units cnr4_T_C = deg_C

C-2

Appendix C. CR3000 Program for Measuring Pt-100 Temperature Sensor

Units cnr4_T_K = K
Units long_up_corr = W/m^2
Units long_dn_corr = W/m^2
Units Rs_net = W/m^2
Units Rl_net = W/m^2
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 'unique sensitivity for lower pyranometer
) '(microV/W/m^2
Const pyrgeometer_up_sensitivity = 8.50 'unique sensitivity for upper pyrgeometer
oV/W/m^2) '(micr
Const pyrgeometer_ n_sensi vity for lower pyrgeometer d tivity = 7.09 'unique sensiti
'(microV/W/m^2)

'CNR4 multipliers
Public cnr4_mult(4)
Const pyranometer_ p_mult 2/mV) u = 1000/pyranometer_up_sensitivity '(W/m^
Const pyranometer_ n_mult 2/mV) d = 1000/pyranometer_dn_sensitivity '(W/m^
Const pyrgeometer_ p_mult 2/mV) u = 1000/pyrgeometer_up_sensitivity '(W/m^
Const pyrgeometer_ n_mult m^2/mV) d = 1000/pyrgeometer_dn_sensitivity '(W/

DataTable (cnr4_da a,True,t -1)
DataInterval (0, ,Min,160 0)
CardOut (1,-1)
Minimum (1,batt_vo ,0,False) lt,FP2
Sample (1,logger_temp,FP2)
Average (4,cnr4(1),IEEE4,False)
Average (1,cnr4_T_C,IEEE4,False)
Average (1,cnr4_T_K,IEEE4,False)
Average (1,long_up_corr,IEEE4,False)
Average (1,long_dn_corr,IEEE4,False)
Av s_net,IEEE4,False)erage (1,R
Average (1,Rl_net,IEEE4,False)
Average (1,albedo,IEEE4,False)
Average (1,Rn,IEEE4,False)
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) = pyranom _mult eter_up
cnr4_mult(2) = pyranom _mult eter_dn
cnr4_mult(3) = pyrgeome _mult ter_up
cnr4_mult(4) = pyrgeom mult eter_dn_

Sca c,3,0) n (1,Se
PanelTemp (logger_temp,250)
Battery (batt_volt)

'CNR4 radiation measurements
VoltDiff (cnr4(),4,mV20C,1,True ,0,_60Hz,cnr4_mult(),0)

C-3

Appendix C. CR3000 Program for Measuring Pt-100 Temperature Sensor

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+5.67e-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_data
CallTable cnr4_ts

NextScan
EndProg

easurement 'PRT (Pt-100) temperature m

C-4

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