Campbell Scientific Kipp and Zonen CMP User Manual
CMA series
Albedometer
CMP series
Pyranometer
Instruction Manual
IMPORTANT USER INFORMATION
Reading this entire manual is recommended for full understanding of
the use of this product.
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, The Netherlands
or P.O. Box 507, 2600 AM Delft, The Netherlands
T : +31 (0)15 2755210
F : +31 (0)15 2620351
E : info@kippzonen.com
W : www.kippzonen.com
Kipp & Zonen reserves 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 used, rising from the faulty and incorrect use of the product.
User made modifications can affect the validity of the CE declaration.
COPYRIGHT© 2006 KIPP & ZONEN
All rights are 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: 0806
Page 1
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 products
Type: CMP 3 / CMP 6 / CMP 11 / CMP 21 / CMP 22
Name: Pyranometer
and
Type: CMA 6 / CMA 11
Name: Albedometer
to which this declaration relates are 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.
B.A.H. Dieterink
President
KIPP & ZONEN B.V.
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CMP/CMA series manual
Table of Contents
IMPORTANT USER INFORMATION.......................................................................................................1
Declaration of Conformity.........................................................................................................................2
Table of Contents .....................................................................................................................................3
1. Introduction....................................................................................................................................5
2. Installation and operation...............................................................................................................6
2.1. Delivery..........................................................................................................................................6
2.2. Mechanical installation...................................................................................................................6
2.2.1. Installation for measurement of global radiation........................................................................6
2.2.2. Installation for measurement of radiation on inclined surfaces..................................................8
2.2.3. Installation for measurement of reflected radiation....................................................................8
2.2.4. Installation for measurement of diffuse radiation.......................................................................9
2.2.5. Installation for measurement of albedo......................................................................................9
2.2.6. Underwater use..........................................................................................................................9
2.3. Electrical installation ....................................................................................................................10
2.4. Operation.....................................................................................................................................11
2.5. Measurement uncertainty............................................................................................................11
2.6. Maintenance ................................................................................................................................13
3. Principle components of pyranometers.......................................................................................14
3.1. Dome ...........................................................................................................................................14
3.2. Detector .......................................................................................................................................15
3.3. Housing........................................................................................................................................15
3.4. Drying cartridge............................................................................................................................15
3.5. Cable and connector....................................................................................................................15
4. Pyranometer physical properties.................................................................................................16
4.1. Spectral range..............................................................................................................................16
4.2. Sensitivity.....................................................................................................................................16
4.3. Impedance...................................................................................................................................16
4.4. Response time.............................................................................................................................16
4.5. Non-linearity.................................................................................................................................17
4.6. Temperature dependence ...........................................................................................................17
4.7. Tilt error........................................................................................................................................17
4.8. Zero offset A ................................................................................................................................17
4.9. Zero offset B ...............................................................................................................................18
4.10. Operating temperature.............................................................................................................18
4.11. Field of view .............................................................................................................................18
4.12. Directional response ................................................................................................................18
4.13. Maximum irradiance.................................................................................................................18
4.14. Non-stability..............................................................................................................................19
4.15. Spectral selectivity ...................................................................................................................19
4.16. Environmental..........................................................................................................................19
4.17. Uncertainty...............................................................................................................................19
5. Calibration....................................................................................................................................20
5.1. Calibration principle .....................................................................................................................20
5.2. Calibration procedure at Kipp & Zonen .......................................................................................20
5.2.1. The calibration facility...............................................................................................................20
5.2.2. Calibration procedure...............................................................................................................20
5.2.3. Calculation................................................................................................................................21
5.2.4. Zero offset................................................................................................................................21
5.3. Traceability to World Radiometric Reference..............................................................................21
5.4. Recalibration................................................................................................................................21
6. CMP/CMA models.......................................................................................................................23
6.1. CMP 6 / CMA 6............................................................................................................................23
6.2. CMP 11 / CMA 11........................................................................................................................23
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CMP/CMA series manual
CMP 21........................................................................................................................................24
6.3.
6.4. CMP 22........................................................................................................................................24
6.5. CMP / CMA series performance specifications...........................................................................25
6.6. CMP / CMA series general specifications ...................................................................................26
7. Frequently asked questions.........................................................................................................27
8. Trouble shooting..........................................................................................................................28
Appendix I Radiometric terminology.......................................................................................................29
Appendix II 10k thermistor specifications...............................................................................................30
Appendix III Pt-100 specifications ..........................................................................................................31
Appendix IV classification According to WMO Guide 1996....................................................................32
Appendix V List of World and Regional Radiation Centres....................................................................33
Appendix VI Recalibration service..........................................................................................................34
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CMP/CMA series manual
1. Introduction
Dear customer, thank you for purchasing a Kipp & Zonen instrument. Please read this manual and the
separate instruction sheet for a full understanding of the use of your pyranometer or albedometer.
A CMP series pyranometer or CMA series albedometer is a high quality radiometer designed for
measuring short-wave irradiance on a plane surface (radiant flux, W/m
direct solar radiation and the diffuse radiation incident from the hemisphere above the instrument.
According to International Standard ISO 9060 and the World Meteorological Organisation (WMO) a
pyranometer is the designated type of instrument for the measurement of global or diffuse solar
radiation. All pyranometers and albedometers within the CMP/CMA series are compliant with one of
the classes specified by the international standards.
This manual, together with the instruction sheet, gives information related to installation, maintenance,
calibration, product specifications and applications of the CMP/CMA series. Note that the smaller CMP
3 pyranometer with a single glass dome is largely excluded from this manual due to the different
construction. However, the general definitions and principles also apply to this model.
If any questions should remain, please feel free to contact your Kipp & Zonen dealer or e-mail
info@kippzonen.com
For information about other Kipp & Zonen products or to check for any update of this manual, g o to
www.kippzonen.com
2
) which results from the sum of
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CMP/CMA series manual
2. Installation and operation
2.1. Delivery
Check the contents of the shipment for completeness (see below) and note whether any damage has
occurred during transport. If there is damage, a claim should be filed with the carrier immediately. In
this case, or if the contents are incomplete, your dealer should be notified in order to facilitate the
repair or replacement of the instrument.
Contents of delivery:
1. Radiometer
2. Sun shield
3. Cable with connector
4. Test reports
5. Instruction sheet
6. Radiometer fixing kit
7. 2 x desiccant bags
8. Product documentation CD
Although all CMP/CMA radiometers are weatherproof and suitable for harsh environmental conditions,
they have some delicate mechanical parts. Please keep the original packaging for safe transport of the
radiometer to the measurement site or for use when returning the radiometer for calibration.
The calibration certificate supplied with the instrument is valid for 1 year from the date of first use by
the customer, subject to the variations in performance due to specific operating conditions that are
given in the instrument specifications. The calibration certificate is dated relative to the time of
manufacture, or recalibration, but the instrument does not undergo any sensitivity changes when kept
in the original packing and not exposed to light. From the moment the instrument is taken from its
packaging and exposed to irradiance the sensitivity will deviate slightly with time. See the 'non-stability'
performance (maximum sensitivity change per year) given in the radiometer specification list.
2.2. Mechanical installation
The mechanical installation of the radiometer depends upon the measuring purpose. Different
measuring methods will be explained in the next paragraphs.
2.2.1. Installation for measurement of global radiation
The following steps must be carefully taken for optimal performance of the instrument.
1. Desiccant
Check the condition of the desiccant and replace if necessary, for example after a long storage period.
2. Location
Ideally the site for the radiometer should be free from any obstructions to the horizon above the plane
of the sensing element. If this is not possible, the site should be chosen in such a way that any
obstruction over the azimuth range between earliest sunrise and latest sunset should have an
elevation not exceeding 5
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o
(the apparent sun diameter is 0.5o).
CMP/CMA series manual
This is important for an accurate measurement of the direct solar radiation. The diffuse solar radiation
is less influenced by obstructions near the horizon. For instance, an obstruction with an elevation of 5
over the whole azimuth range of 360
o
decreases the downward diffuse solar radiation by only 0.8%.
o
The radiometer should be readily accessible for cleaning the outer dome and inspectin g the desiccant
It is evident that the radiometer should be located in such a way that a shadow will not be cast upon it
at any time (for example by masts or ventilation ducts). Note that hot exhaust gas (> 100
o
C) will
produce some radiation in the spectral range of the radiometer and cause an offset in the
measurements. The radiometer should be distant from light-coloured walls or other objects likely to
reflect sunlight onto it, or emitting short-wave radiation.
3. Mounting
The CMP pyranometer is provided with two holes for 5 mm bolts. Two each of stainless steel bolts,
washers, nuts and nylon insulation rings are provided in the fixing kit. The pyranometer should first be
secured lightly with the bolts to a solid and stable mounting stand or platform as shown in Figure 1.
After recalibration the nylon insulators must be replaced with new ones to prevent corrosion.
The mounting stand temperature can vary over a wider range than the air temperature. Temperature
fluctuations of the pyranometer body can produce offset signals, therefore it is recommended to isolate
the pyranometer thermally from the mounting stand by placing it on its levelling screws. Ensure that
there is a good electrical contact with earth to conduct away currents in the cable shield induced by
lightning.
Figure 1 Pyranometer installation
Note: After recalibration and/or reinstallation the nylon insulators must be replaced with new ones to
maintain durability.
4. Orientation
In principle no special orientation of the instrument is required, although the World Meteorological
Organisation (WMO) recommends that the signal lead is pointed towards the nearest pole, to minimise
heating of the electrical connections.
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CMP/CMA series manual
5. Level pyranometer
Accurate measurement of the global radiation requires proper levelling of the thermopile surface. Level
the instrument by turning the two levelling screws to bring the bubble of the spirit level centrally within
the marked ring. For easy levelling, first use the screw nearest to the spirit level. When the
pyranometer is placed horizontally using the bubble level, or when it is mounted with its base directly
on a horizontal plane, the thermopile is horizontal within 0.1
o
.
6. Secure pyranometer
Secure the pyranometer tightly with the two stainless steel bolts. Ensure that the pyranometer
maintains the correct levelled position!
7. Fit cable and sun shield
Locate the cable plug correctly in the radiometer socket (it only fits one way) and screw the plug
locking ring hand-tight. Finally, clip on the sun shield to prevent excessive heating of the radiometer
body. The bubble level is visible through the top of the sun shield for routine checks.
2.2.2. Installation for measurement of radiation on inclined surfaces
It is advised to pre-adjust the levelling screws on a horizontal surface for easy orientation of the
instrument parallel to the inclined surface. Because the temperature of the mounting stand is expected
to rise considerably (more than 10
o
C above air temperature), the body must be thermally isolated by
the levelling screws from the stand. This will promote a thermal equilibrium between domes and body
and decrease zero offset signals.
2.2.3. Installation for measurement of reflected radiation
In the inverted position the pyranometer measures reflected
global radiation. According to the WMO the height should be 1
m to 2 m above a uniform surface covered by short grass.
The mounting device should not interfere significantly with the
field of view of the instrument. The upper plate prevents
excessive heating of the pyranometer body by the solar
radiation and, if large enough, it keeps the lower screen free of
precipitation. The lower glare screen prevents direct
illumination of the domes by the sun at sunrise and sunset and
is available as an accessory kit for the CMP series.
Offset signals generated in the pyranometer by thermal effects
are a factor of 5 more significant in the measurement of
reflected radiation due to the lower irradiance level. The mast
shown in Figure 2 intercepts a frac tion D/2πS. of the radiation
coming from the ground. In the most unfavourable situation
(sun at zenith) the pyranometer shadow decreases the signal
by a factor R
2/H2
.
A rule of thumb is:
A black shadow with radius = 0.1 H on the field below decreases the signal by1% and 99% of the
signal will originate from an area with radius 10 H.
Figure 2 Mast construction
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CMP/CMA series manual
2.2.4. Installation for measurement of diffuse radiation
For measuring sky radiation, the direct solar radiation is
intercepted by a small disk or sphere. The shadow of the disk
must cover the pyranometer domes completely. However, to
follow the sun's apparent motion, a power-driven tracking device
is necessary as shown in Figure 3.
This can be done using a Kipp & Zonen sun tracker, such as the
model 2 AP, designed to track the sun accurately under all
weather conditions. More information about the combination of
pyranometer and tracker is given in the sun tracker manual.
Alternatively, a static shadow ring can be used to intercept the
direct solar radiation; but it is less accurate and may require
periodic manual adjustment. At times the shadow ring also
intercepts a proportion of the diffuse sky radiation. Therefore,
Figure 3 2AP Sun Tracker with
shaded pyranometer
corrections for this to the recorded data are necessary.
Kipp & Zonen produces a universal shadow ring, model CM 121, which is suitable for use at all
latitudes. In the CM 121 manual, installation instructions and correction factors are given.
2.2.5. Installation for measurement of albedo
An albedometer measures both the global solar radiation and the
reflected radiation form the surface below. It can be configured
from two CMP series pyranometers and a suitable mounting
plate, or by using a CMA series integrated albedometer.
The requirements for installation of the upper and lower
pyranometers are the same as in paragraphs 2.2.1 and 2.2.3 for
global and reflected radiation. A typical arrangement is shown in
Figure 4. According to the WMO the height should be 1 m to 2 m
above a uniform surface covered by short grass.
Installation of the CMA series differs slightly because there are
no levelling screws. The integrated mounting rod is fixed to the
mast. CMA has an integrated lower glare screen to prevent
direct illumination of the domes by the sun at sunrise and sunset.
The mast shown intercepts a fraction D/2πS of the radiation that Figure 4 Albedo configuration
is coming from the ground. In the most unfavourable situation
(sun at zenith) the pyranometer shadow decreases the signal by
a factor R
2/H2
.
2.2.6. Underwater use
The CMP/CMA radiometers are in principle watertight according to the IP 67 standard. However, the
hemispherical air cavity under the dome(s) acts as a negative lens. The parallel beam of direct solar
radiation becomes divergent after the passage of the outer dome. Consequently the intensity at the
sensor is lower than outside the dome(s). The calibrated sensitivity figure is not valid in this case and
must be derived empirically.
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CMP/CMA series manual
2.3. Electrical installation
As standard the CMP/CMA is supplied with a waterproof connector pre-wired to 10 m cable with a
number of leads and a shield covered with a black sleeve. The number of connector pins and cable
leads depends upon the model of radiometer and whether a temperature sensor is fitted (and which
type). The colour code of the wires and the connector pin numbers are shown on the instruction sheet.
Longer cables are available as options.
Preferably, secure the radiometer with its levelling screws or mounting rod to a metal support with a
good connection to earth (e.g. by using a lightning conductor).
The shield of the cable is connected to the aluminium radiometer housing through the connector body.
The shield at the cable end may be connected to ground at the readout equipment. Lightning can
induce high voltages in the shield but these will be led off at the pyranometer and data logger.
Kipp & Zonen pyranometer cables are of low noise type, but bending the cable produces small voltage
spikes, a tribo-electric and capacitance effect. Therefore, the cable must be firmly secured to minimise
spurious responses during stormy weather.
The impedance of the readout equipment loads the temperature compensation circuit and the
thermopile. It can increase the temperature dependency of the pyranometer. The sensitivity is affected
more than 0.1% when the load resistance is less than 100 kΩ. For this reason we recommend the use
of readout equipment with an input impedance of 1 MΩ or more. The solar integrators, data loggers
and chart recorders from Kipp & Zonen meet these requirements.
Long cables may be used, but the cable resistance must be smaller than 0.1% of the impedance of the
readout equipment. It is evident that the use of attenuator circuits to modify the calibration factor is not
recommended because the temperature response will also be affected.
A high input bias current at the readout equipment can produce several micro-Volts across the
impedance of the pyranometer and cable. The zero offset can be verified by replacing the pyranometer
impedance at the readout equipment input terminals with a resistor.
The pyranometer can also be connected to a computer or data acquisition system. A low voltage
analogue input must be available. The resolution of the Analogue-to-Digital Converter (ADC) must
allow a system sensitivity of about 1 bit per W/m
solar radiation measurements, because pyranometers exhibit offsets up to ± 2 W/m
thermal equilibrium.
For amplification of the pyranometer signal Kipp & Zonen offers the AMPBOX signal amplifier. This
amplifier will convert the micro-Volt output from the pyranometer into a standard 4 – 20 mA signal. The
use of the AMPBOX amplifier is recommended for applications with long cables (> 100 m), electrically
noisy environments or data loggers with a current-loop input. The AMPBOX can be factory adjusted to
suit the sensitivity of an individual radiometer to produce a defined range, typically 4 – 20 mA
represents 0 – 1600 W/m
2
. The CMA series have two independent signal outputs, so two AMPBOX
amplifiers are required.
2
. More resolution is not necessary during outdoor
2
due to lack of
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