Kipp&Zonen CNR 4 User Manual
CNR 4
Net Radiometer
Instruction Manual
1
IMPORTANT USER INFORMATION
Reading this entire manual is recommended for full understanding of the use of this product.
The exclamation mark within an equilateral triangle is intended to alert the user to the presence of important
operating and maintenance instructions in the literature accompanying the instrument.
Should you have any comments on this manual we will be pleased to receive them at:
Kipp & Zonen B.V.
Delftechpark 36
2628 XH Delft
P.O. Box 507
2600 AM Delft
The Netherlands
+31 15 2755 210
info@kippzonen.com
www.kippzonen.com
Kipp & Zonen reserve the right to make changes to the specifications without prior notice.
WARRANTY AND LIABILITY
Kipp & Zonen guarantees that the product delivered has been thoroughly tested to ensure that it meets its published
specifications. The warranty included in the conditions of delivery is valid only if the product has been installed and
used according to the instructions supplied by Kipp & Zonen.
Kipp & Zonen shall in no event be liable for incidental or consequential damages, including without limitation, lost
profits, loss of income, loss of business opportunities, loss of use and other related exposures, however caused,
arising from the faulty and incorrect use of the product.
User made modifications can affect the validity of the CE declaration.
COPYRIGHT
©
2014 KIPP & ZONEN
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any
form or by any means, without permission in written form from the company.
Manual version: 1409
2
DECLARATION OF CONFORMITY
According to EC guideline 89/336/EEC 73/23/EEC
We: Kipp & Zonen B.V.
Delftechpark 36
2628 XH Delft
The Netherlands
Declare under our sole responsibility that the product
Type: CNR 4
Name: Net Radiometer
And
Type: CNF 4
Name: Ventilation Unit
To which this declaration relates is in conformity with the following standards
Imissions EN 50082-1 Group standard
Emissions EN 50081-1 Group standard
EN 55022
Safety standard IEC 1010-1
Following the provisions of the directive
3
CONTENTS
IMPORTANT USER INFORMATION ................................................................................................................................... 1!
DECLARATION OF CONFORMITY ..................................................................................................................................... 2!
CONTENTS ................................................................................................................................................................................. 3!
1! GENERAL INFORMATION ............................................................................................................................................ 4!
1.1! Connecting the CNR 4 ............................................................................................................ 5!
1.1.1! The difference between temperature and sensor connection ........................................... 5!
1.1.2! The radiometer Sensor connector (S) ............................................................................... 5!
1.1.3! The radiometer Temperature connector (T) ..................................................................... 7!
1.1.4! The (optional) CNF 4 connector ....................................................................................... 8!
1.1.5! Using the CNR 4 calibration factors ................................................................................. 8!
1.1.6! Using the CNR 4 measuring Net Radiation ....................................................................... 9!
1.1.6.1! Measuring Solar radiation with the pyranometer ........................................................................... 9!
1.1.6.2! Measuring Far Infrared radiation with the pyrgeometer ................................................................ 9!
1.1.6.3! Measuring the CNR 4's body temperature ..................................................................................... 9!
1.1.6.4! Calculation of the albedo for solar radiation ............................................................................... 12!
1.1.6.5! Calculation of the Net Solar radiation ......................................................................................... 12!
1.1.6.6! Calculation of the Net (total) radiation ........................................................................................ 13!
2! CNR 4 PROPERTIES ..................................................................................................................................................... 16!
2.1! Properties of the CNR 4 Net-Radiometer ............................................................................... 16!
2.1.1! Specifications of the CNR 4 ........................................................................................... 17!
2.2! Properties of the pyranometer .............................................................................................. 17!
2.2.1! Specifications of the pyranometer ................................................................................. 18!
2.2.2! Spectral properties of the pyranometer ......................................................................... 20!
2.2.3! Directional / Cosine response of the pyranometer ......................................................... 20!
2.3! Properties of the pyrgeometer .............................................................................................. 22!
2.3.1! Window heating offset .................................................................................................. 22!
2.3.2! Water deposition on the pyrgeometer window ............................................................... 22!
2.3.3! Specifications of the Pyrgeometer ................................................................................. 22!
2.3.4! Spectral properties of the pyrgeometer ......................................................................... 24!
2.3.5! Directional / Cosine response of the pyrgeometer ......................................................... 24!
2.4! Properties of the CNF 4 (optional) ventilation unit ................................................................ 25!
2.4.1! CNF 4 specifications ...................................................................................................... 25!
2.5! Properties of the Pt-100 and thermistor ................................................................................ 26!
3! CALIBRATION ................................................................................................................................................................ 27!
3.1! Calibration of the pyranometers ........................................................................................... 27!
3.2! Calibration of the pyrgeometers ........................................................................................... 27!
3.3! Recalibration of pyranometers and pyrgeometers ................................................................. 27!
3.4! Checking the Pt-100 and Thermistor .................................................................................... 27!
4! INSTALLATION AND MAINTENANCE ................................................................................................................... 28!
4.1! Replacing the drying cartridge ............................................................................................. 28!
4.2! Replacing the Ventilator Filter .............................................................................................. 29!
5! TROUBLE SHOOTING .................................................................................................................................................. 30!
5.1! Testing the pyranometer ...................................................................................................... 30!
5.2! Testing of the pyrgeometer .................................................................................................. 30!
5.3! Testing the Pt-100 ................................................................................................................ 31!
5.4! Testing the thermistor ......................................................................................................... 31!
5.5! Testing the Heater ............................................................................................................... 31!
5.6! Testing the Ventilator .......................................................................................................... 31!
6! CMB 1 OPTIONAL MOUNTING BRACKET ........................................................................................................... 32!
7! DELIVERY ........................................................................................................................................................................ 34!
8! RECALIBRATION SERVICE ......................................................................................................................................... 35!
4
1 GENERAL INFORMATION
The CNR 4 is a 4 component net radiometer that measures the energy balance between incoming short-wave
and long-wave Far Infrared (FIR) radiation versus surface-reflected short-wave and outgoing long-wave radiation.
The CNR 4 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 the short-wave radiation. And the
pyrgeometer pair measures long-wave radiation. The upper long-wave detector of CNR 4 has a meniscus dome. This
ensures that water droplets role off easily and improves the field of view to nearly 180°, compared with a 150° for a
flat window. All 4 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 Pt-100 and Thermistor, are integrated for compatibility with every data logger. 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 assures that the temperatures of the measurement surfaces are the same and accurately
known. This improves the quality of the long-wave measurements.
The design is very light in weight and has an integrated sun shield that reduces thermal effects on both long-wave
and short-wave measurements. The cables are yellow with waterproof connectors as used with all our new
radiometers. The mounting rod can be unscrewed for transport, like the CNR 2.
An optional ventilation unit with heater is designed as an extension of the sunshield and can be fitted new to the
CNR 4 or retro-fitted later. The ventilation unit CNF 4 is compact and provides efficient air-flow over the domes and
windows to minimize the formation of dew and reduce the frequency of cleaning. The integrated heater can be used
to melt frost.
The CNR 4 specifications when used with CNF 4 comply with the WMO classification of Good Quality
The Net Radiometer, CNR 4, is intended for the analysis of the radiation balance of Solar and Far Infrared radiation.
The most common application is the measurement of Net (total) Radiation at the earth's surface.
The CNR 4 design is such that both the upward facing and the downward-facing instruments measure the energy
that is received from the whole hemisphere (180 degrees field of view). The output is expressed in Watts per square
meter. The total spectral range that is measured is roughly from 0.3 to 42 micrometers. This spectral range covers
both the Solar Radiation, 0.3 to 3 micrometers, and the Far Infrared radiation, 4.5 to 42 micrometers.
Chapter 1 describes how to operate the CNR 4, giving separate attention to the use of the individual pyranometers
and pyrgeometers. More about the physics of the pyranometer and pyrgeometer can be found in chapter 2.
The CNR 4 radiometers all have individual calibration factors. As opposed to the CNR 1 they are not made equal.
The advantage is that the individual sensitivities are more accurate then when made equal with shunt and series
resistors.
For quality assurance of the measurement data, we recommend the recalibration of the CNR 4 as part of a regular
maintenance schedule every two years. More about calibration can be found in chapter 3.
The CNR 4 is intended for continuous outdoor use. It is weatherproof. The materials used in Pyranometer and
pyrgeometer are robust. Contrary to most competitive instruments, plastic domes are not used. Therefore the CNR
4 requires very low maintenance. For optimal results however, proper care must be taken. More about maintenance
can be found in chapter 4. Chapter 5 can be consulted if a problem with the CNR 4 is suspected; this chapter
addresses trouble shooting.
The general user should read chapter 1 and chapter 4.
5
1.1 Connecting the CNR 4
1.1.1 The difference between temperature and sensor connection
CNR 4 has several output signals: two voltages for the pyranometers, two voltages for the pyrgeometers, and two
temperature sensors as standard: a 4 wire Pt-100 connection and a 2 wire connection for the 10k thermistor.
Depending on the used data logger one of the temperature sensors can be used.
The connector with the 4 sensor outputs is indicated with an S on the back of the CNR 4, the temperature connector
is indicated with a T. The sensor connector has 8 pins and 8 wires are coming out of the cable on the other end.
The Temperature connector has also 8 pins but only 6 wires are coming out of the cable.
Exchanging the connectors will not damage the CNR 4. To prevent mix up of the cables after installation it is
advised to mark the cables with a permanent marker or tape showing also S and T.
Figure 1.1 Back of the CNR 4 with the connector for sensor outputs on the left, the temperature connector on the
right and mounting rod in the middle.
1.1.2 The radiometer Sensor connector (S)
CNR 4 sensor connector carries the signals for the two pyranometers and two pyrgeometers. The pin numbers and
wire colours are indicated in the diagram below. The shield of the cable is twisted together and covered with a black
sleeve. If the CNR 4 (rod) is grounded to the mast it is advised not to connect the shielding on the data logger side.
This might cause ground loops and offsets in the signal.
6
Figure 1.2 The sensor connections of the CNR 4. The sensor has four mV outputs, 2 for the pyranometers and 2 for
the pyrgeometers
Ground *
Erde
Terre
Tierra
Red
Rot • Rouge • Rojo
Wire
Kabel
Fil
Cable
White
Weiss • Blanc • Blanco
Brown
Braun • Brun • Marrón
Black
Schwarz • Noir • Negro
Grey
Grau • Gris • Gris
Function
Funktion
Fonction
Función
Pyranometer Upper
Oben • Supérieur • Superior
Pyranometer Lower
Unten • Inférieur • Más bajo
Pyrgeometer Upper
Oben • Supérieur • Superior
Pyrgeometer Lower
Unten • Inférieur • Más bajo
Blue
Blau • Bleu • Azul
Connect with
Anschluss an
Relier à
Conectar con
Yellow
Gelb • Jaune • Amarillo
Green
Grün • Vert • Verde
Housing
Gehäuse
Boîte
Cubierta
Shield
Abschirmung
Protection
Malla
+ Hi
+ Hi
+ Hi
+ Hi
-
Lo
-
Lo
CNR 4 NET RADIOMETER • SENSOR
8 WIRE CABLE • 8-ADRIGES KABEL • CÂBLE 8 FILS • CABLE DE 8 CONDUCTORES
-
Lo
-
Lo
+
-
-
-
-
+
+
+
* Connect to ground if radiometer not grounded
Mit Erde verbinden, wenn das Radiometer nicht geerdet ist
Reliez à la terre si le radiomètre n'est pas connecté
Conectar a tierra si el radiómetro no lo está
1
2
345
6
7
8
1
2
7
8
5
4
6
3
7
1.1.3 The radiometer Temperature connector (T)
The temperature connector of the CNR 4 carries the signals for the PT-100 and Thermistor. The PT-100 and
Thermistor have identical accuracy, the reason for selecting one or the other is mainly the data logger involved. The
Pt-100 temperature sensor has 4 wires, two for the measuring current and two for measuring the voltage over the
resistor (100 Ohm @ 0 °C) . In this way the measurement accuracy is minimally affected by the cable length. The
thermistor has a higher impedance of 10 kOhm and is therefore less influenced by cable length but has no
compensation for it. The shield of the cable is twisted together and covered with a black sleeve. If the CNR 4 (rod)
is grounded to the mast it is advised not to connect the shielding on the data logger side. This might cause ground
loops and offsets in the signal.
Figure 1.3 The temperature connections of the CNR 4. The instrument has one (4-wire) Pt-100 output and a
Thermistor with a 2-wire connection.
CNR 4 NET RADIOMETER • TEMPERATURE
6 WIRE CABLE • 6-ADRIGES KABEL • CÂBLE 6 FILS • CABLE DE 6 CONDUCTORES
7
8
5
3
4
6
Grey
Grau • Gris • Gris
Combined
Kombiniert
Combiné
Combinado
Pt-100
Standard
Standard
Etalon
Estándar
Combined
Kombiniert
Combiné
Combinado
Brown
Braun • Brun • Marrón
Green
Grün • Vert • Verde
Yellow
Gelb • Jaune • Amarillo
White
Weiss • Blanc • Blanco
Thermistor
Standard
Standard
Etalon
Estándar
Black
Schwarz • Noir • Negro
1
2
345
6
7
8
Ground *
Erde
Terre
Tierra
Housing
Gehäuse
Boîte
Cubierta
Shield
Abschirmung
Protection
Malla
8
1.1.4 The (optional) CNF 4 connector
The optional ventilator CNF 4 for the CNR 1 has separate wires for heating and ventilation. In case the heater is
used also the ventilator should be active. The other way around the ventilator can be used without heating. When
the ventilation unit is mounted later on the CNR 4, the extra bottom plate mounts to the bottom of the CNR 4. The
(S) and (T) cables run on both sides of the ventilator to the back of the CNF 4 housing. The extra cover that comes
with the CNF 4 slides under the CNR 4 cover. The 4 pins connector on the back of the CNF 4 is shown below. The
CNR 4 without CNF 4 is supplied with an extra serial number label. This can be used to put on the bottom of the
CNF 4 when mounted (later) on the CNR 4.
Figure 1.3 The heater and ventilator connections of the CNF 4.
1.1.5 Using the CNR 4 calibration factors
The pyranometer generates a mV signal that is simply proportional to the incoming solar Radiation. The conversion
factor between voltage, V, and Watts per square metre of solar irradiance E, is the so-called calibration constant C
(or sensitivity).
For each pyranometer E = V/C (1.1)
When using the pyrgeometer, you should realise that the signal that is generated by the pyrgeometer represents the
exchange of 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. This means that
for estimating the Far Infrared radiation that is generated by the object that is faced by the pyrgeometer, usually the
sky or the soil, you will have to take the pyrgeometer temperature, T, into account. This is why a the temperature
sensors are incorporated in the CNR 4's body near the pyrgeometer sensing element, and has therefore the same
temperature as the pyrgeometer sensor surface. The calculation of the Far Infrared irradiance, E, is done according
to the following equation:
For the pyrgeometer only E = V/C + 5.67⋅10-8*T4 (1.2)
In this equation C is the sensitivity of the sensor. Please bear in mind that T is in Kelvin, and not in Celsius or
Fahrenheit.
Red
Rot • Rouge • Rojo
Wire
Kabel
Fil
Cable
Green
Grün • Vert • Verde
Yellow
Gelb • Jaune • Amarillo
Function
Funktion
Fonction
Función
5 Watt ventilator 12 VDC
Ventilator • Ventilateur • Ventilador
10 Watt heater 12 VDC
Heizung • Chauffage • Calentador
Blue
Blau • Bleu • Azul
Connect with
Anschluss an
Relier à
Conectar con
+
-
-
+
2
4
1
3
CNF 4 VENTILATION UNIT
(OPTIONAL • OPTION • OPTION • OPCIONAL)
4 WIRE CABLE • 4-ADRIGES KABEL • CÂBLE 4 FILS • CABLE DE 4 CONDUCTORES
Ground *
Erde
Terre
Tierra
Housing
Gehäuse
Boîte
Cubierta
Shield
Abschirmung
Protection
Malla
1
2
3
4
9
1.1.6 Using the CNR 4 measuring Net Radiation
In the CNR 4 all components are measured separately. This implies that you should connect all individual
radiometers and one of the temperature sensors. The two pyranometers will measure the solar radiation, both
incoming and reflected, the two pyrgeometers will measure the Far Infrared radiation. For proper analysis of the
pyrgeometer measurement results, they must be temperature corrected using the temperature measurement. The
following paragraphs describe how you should treat the instrument, and how different parameters like net Solar
radiation, net Far Infrared radiation, soil temperature, sky temperature, and Net (total) radiation can be calculated.
Because all radiometers have different sensitivities it is not possible to interconnect the outputs to get the total Net
Radiation.
1.1.6.1 Measuring Solar radiation with the pyranometer
Measuring with a pyranometer can be done by connecting two pyranometer wires, + and -, to a voltmeter. Incidental
light results in a positive signal. The pyranometer mounting plate and ambient air should be at the same
temperature, as much as possible. Conversion of the voltage to irradiance can be done according to equation 1.1.
This is sometimes done in the data logging system itself, sometimes during evaluation in the user's software.
Measuring with the upward-facing pyranometer, the so-called global (solar) radiation is measured. The downwardfacing pyranometer measures the reflected solar radiation. When calculating the Net radiation, the Reflected
radiation must be subtracted from the global radiation. See 1.1.6.5.
1.1.6.2 Measuring Far Infrared radiation with the pyrgeometer
A measurement with the pyrgeometer can be performed by connecting two pyrgeometer wires, + and -, to a voltmeter. A signal radiating from a source which is warmer than the pyrgeometer results in a positive signal.
To measure the Far Infrared irradiances with the two pyrgeometers, separately the Pt-100 output is required. The
formula 1.2 is used to calculate the Far Infrared irradiance of the sky and of the ground.
With the downward-facing pyrgeometer, you would generally measure the Far Infrared radiation that is emitted by
the ground. In contrast, the upward-facing pyrgeometer is generally used to measure the Far Infrared radiation from
the sky. As the sky is typically colder than the instrument, you can expect negative voltage signals from the upwardfacing pyrgeometer.
1.1.6.3 Measuring the CNR 4's body temperature
The CNR 4 has two temperature sensors built in as standard. The main reason to choose between the Pt-100 or the
Thermistor is the connected data logger.
Some data loggers have inputs for thermistors some only for thermistors some have both.
Check carefully the correct sensor regarding to the data logger. There is no difference in accuracy.
The Pt-100 however can be used in 4 wire mode as is therefore compensated for longer wires.
The Thermistor has itself higher impedance (10k) and is less susceptible for longer wires, but can not be
compensated for it.
To obtain a signal from the Pt-100, a current of about 1 mA is fed through two wires on either side of the PT-100.
The voltage that is generated must be measured using the other pair of wires which are connected in parallel with
the PT-100.This is known as a 4-wire measurement. Measuring in this manner eliminates errors during measurement, which would be produced by additional wire length. Some systems have a 3-wire connection. In this case omit
one current lead and follow the instructions of your measurement system manual. Table 1.1 states the Pt-100
resistance values as a function of temperature. Please note that for use in formula 1.2, you must use Kelvin, not
degrees Celsius or Fahrenheit. Most data acquisition systems have standard readout and conversion for Pt-100's. .
The thermistor resistance values as a function of temperature are indicated in table 1.2.
10
Temperature
[EC]
Resistance
[Ω]
Temperature
[EC]
Resistance
[Ω]
Temperature
[EC]
Resistance
[Ω]
-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
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
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
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
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
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
Table 1.1 Resistance values versus temperature in °C of the CNR 4's Pt-100.
The Pt-100 complies with the class A specifications of DIN.
11
Temperature
[EC]
Resistance
[Ω]
Temperature
[EC]
Resistance
[Ω]
Temperature
[EC]
Resistance
[Ω]
-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
135200
127900
121100
114600
108600
102900
97490
92430
87660
83160
78910
74910
71130
67570
64200
61020
58010
55170
52480
49940
47540
45270
43110
41070
39140
37310
35570
33930
32370
30890
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
29490
28150
26890
25690
24550
23460
22430
21450
20520
19630
18790
17980
17220
16490
15790
15130
14500
13900
13330
12790
12260
11770
11290
10840
10410
10000
9605
9227
8867
8523
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
8194
7880
7579
7291
7016
6752
6500
6258
6026
5805
5592
5389
5193
5006
4827
4655
4489
4331
4179
4033
3893
3758
3629
3504
3385
3270
3160
3054
2952
2854
Table 1.2 Resistance values versus temperature in °C of the CNR 4's thermistor.
Relatively small errors occur when the CNR 4 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 real sensor temperature and Pt-100 or thermistor reading is less than 0.5 degree.
The internal temperature sensors will not give a good indication of ambient air temperature; at 1000 Watts per
square meter Solar Radiation, and no wind, the instrument temperature can rise a few degrees above ambient
temperature. This will not affect the readings of the CNR 4
The offsets of both pyranometers and pyrgeometers might be larger than 5 Watts per square meter if large
temperature gradients are forced on the instrument (larger than 5 K/hr). This happens for example when rain hits
the instrument. The occurrence of this can be detected using the temperature sensor readout. It can be used as a
tool for quality assurance of your data.
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