Kipp & Zonen CGR 4, Instruction Manual

Page 1: ...Instruction Manual Pyrgeometer CGR 4 ...

Page 2: ... 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 howev...

Page 3: ...clare under our sole responsibility that the products Type CGR 3 CGR 4 Name Pyrgeometer 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 Page 3 ...

Page 4: ...iple components of pyrgeometers 3 1 Window 3 2 Detector 3 3 Temperature sensor 3 4 Housing 3 5 Drying cartridge 3 6 Cable and connector 4 Pyrgeometer physical properties 4 1 Spectral range 4 2 Sensitivity 4 3 Impedance 4 4 Response time 4 5 Non linearity 4 6 Temperature dependence 4 7 Tilt error 4 8 Window heating offset 4 9 Zero offset B due to ambient temperature changes 4 10 Operating temperature...

Page 5: ...ype of instrument for the measurement long wave atmospheric radiation This manual together with the instruction sheet gives information related to installation maintenance calibration product specifications and applications of the CGR series Note that the smaller CGR 3 pyrgeometer with a flat infrared window is largely excluded from this manual due to the different construction However the general ...

Page 6: ...ation 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 yea...

Page 7: ...y currents in the cable shield induced by lightning Figure 1 Pyrgeometer 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 neares...

Page 8: ... the dome and the housing and decrease zero offset signals 2 2 3 Installation for measurement of upward long wave radiation In the inverted position the pyrgeometer measures radiation from the ground 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 u...

Page 9: ...olar radiation because the dome heating effect when suitably ventilated is negligible due to the unique construction of the pyrgeometer 2 2 5 Installation for measurement of net long wave radiation A net pyrgeometer measures both the downward atmospheric long wave radiation and the upward long wave radiation from the surface below It can be configured from two CGR series pyrgeometers and a suitable...

Page 10: ...le 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 pyrgeometer and data logger Kipp Zonen pyrgeometer 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 w...

Page 11: ...emitted from the atmosphere and the upward irradiance of the CGR 4 detector Upward irradiance of the CGR 4 detector W m Note that the net radiation term Uemf S is mostly negative so the calculated downward atmospheric long wave radiation is smaller than the detector s upward irradiance This refers to the net radiation within the pyrgeometer not the net radiation as referred to in 2 2 5 In the Base...

Page 12: ...r output will read zero because water deposited on the pyrgeometer window is a perfect infrared absorber A cloudy overcast sky condition is illustrated in Figure 5 Figure 5 Cloudy overcast sky condition 2 4 2 Clear sky Clear sky conditions differ in that there is a relatively large heat loss caused by the atmospheric window The amount of re emitted radiation by a clear sky is smaller compared to th...

Page 13: ...frared detected at the CGR 4 and the CGR 3 is expected to be very low 0 to 3 W m because of the filter cut on at 4 5 µm Other types of pyrgeometers can exhibit 0 10 W m Figure 7 Direct solar irradiance in Davos Switzerland at solar noon in mid September 2 5 Measurement uncertainty When a pyrgeometer is in operation the performance of it is correlated to a number of parameters such as temperature l...

Page 14: ... of a CGR 4 pyrgeometer The temperature dependence of the sensitivity is a function of the individual CGR 4 For a given CGR 4 the response lies in the region between the curved lines in Figure 9 The temperature dependence of each CGR 4 pyrgeometer is characterised and supplied with the instrument Each CGR 4 has a built in temperature sensor to allow corrections to be applied if required Figure 9 T...

Page 15: ...ice of heating levels Note that the CGR 3 pyrgeometer cannot be used with the CV 2 ventilation unit A periodic check is to ensure that the pyrgeometer is level and that the silica gel desiccant is still coloured orange When the orange silica gel in the drying cartridge is turned completely transparent normally after several months it must be replaced by fresh silica gel as supplied in the small re...

Page 16: ... entry level CGR 3 has a flat silicon window to reduce cost A drying cartridge desiccator in the radiometer housing is filled with silica gel and prevents dew on the inner sides of the domes which can cool down considerably on clear windless nights Figure 10 Construction details of CGR 4 pyrgeometer 3 1 Window The inner surface of the silicon dome window has an interference filter deposited on it ...

Page 17: ...ically in series The absorption of thermal radiation by one of the thermocouple junctions called the active or hot junction increases its temperature The differential temperature between the active junction and a reference cold junction kept at a fixed temperature produces an electromotive force directly proportional to the differential temperature created This is a thermoelectric effect The sensitiv...

Page 18: ...umidity level inside the pyrgeometer Initially the desiccant will have an orange colour After some time it becomes saturated with moisture and the colour will change to become clear transparent At this time the contents of the drying cartridge should be replaced with fresh unsaturated orange colored desiccant as soon as possible Replacement desiccant is available through Kipp Zonen distributors 3 ...

Page 19: ...ined in wavelengths less than 4µm called short wave radiation The equivalent radiant temperature of the Earth s surface is about 275K More than 99 of this energy is emitted at wavelengths greater than 3 µm and is called long wave thermal or infrared radiation Downward long wave radiation is a result of atmospheric re emission Re emission is the reversible effect of absorption of long wave radiation...

Page 20: ... pyrgeometer is the percentage deviation in the sensitivity over a net irradiance range from 250 to 250 W m compared to the sensitivity calibration irradiance of 100 W m The non linearity effect is due to convective and radiative heat losses at the black absorber surface which make the conditional thermal equilibrium of the radiometer non linear 4 6 Temperature dependence The sensitivity change of ...

Page 21: ...erial and adhesive increases the mean emission coefficient of the inner dome window surface Its presence increases the window heating offset Under clear skies the direct solar irradiance impacts mainly from one direction so for a hemispherical dome it is recommended to have 3 equally spaced thermistors to determine the mean dome temperature The dome window thermistor s should be carefully matched wit...

Page 22: ... a flat horizontal surface originating from a point source with a defined zenith position will have an intensity value proportional to the cosine of the zenith angle of incidence This is sometimes called the cosine law or cosine response and is very important in the measurement of short wave solar radiation However the directional response of pyrgeometers is largely irrelevant since the hemisphere...

Page 23: ...tal conditions within the specified ranges 4 17 Uncertainty The measurement uncertainty can be described as the maximum expected hourly or daily uncertainty with respect to the absolute truth The confidence level is 95 which means that 95 of the datapoints lie within the given uncertainty interval representing the absolute value Kipp Zonen empirically determine uncertainty figures based on many ye...

Page 24: ...age sensitivity is calculated using the Formula 3 Formula 3 A final St is determined using only one minute St s determined under clear sky conditions when Net IR exchange 40 W m The sum of all periods must be at least 6 hours for a successful calibration 5 3 Traceability to World Radiometric Reference Reference radiometers which are calibrated annually by the World Radiation Centre in Davos are us...

Page 25: ...be simply mounted back to back and an optional mounting rod fitted 6 1 CGR 4 CGR 4 has been designed for scientific measurements outdoors of downward atmospheric long wave radiation with extremely high reliability and accuracy CGR 4 provides an output voltage that is proportional to the net radiation in the far infrared FIR By calculation downward atmospheric long wave radiation is derived CGR 4 h...

Page 26: ...6 2 CGR 4 performance specifications Page 26 CGR 4 Manual ...

Page 27: ...6 3 CGR 4 general specifications CGR 4 Manual Page 27 ...

Page 28: ...ossibly interchanged Is the pyrgeometer sensitivity affected by the length of the signal cable With longer cable lengths the impedance increases however it does not affect the radiometer sensitivity for the following reason The impedance of the voltage measurement device is at east 10000 times more than the impedance of the pyrgeometer plus cable Therefore the current that goes through the readout c...

Page 29: ...oo much water is deposited internally the drying cartridge should be removed and the instrument warmed to dry it Check instrument impedance see specifications for expected values Check data logger or integrator offset by connecting a dummy load 100 Ohm resistor This should give a zero reading Check levelling bubble inside ring If water or ice is deposited on the dome clean it Probably water droplet...

Page 30: ... W m Long wave radiation Radiation with wavelengths 4 µm and 100 µm Long wave downward radiation Radiation emitted by the sky Net radiation Long wave downward radiation minus outgoing radiation Pyrgeometer Radiometer suitable to measure downward long wave radiation Short wave radiation Radiation with wavelengths 280 nm and 4 µm Thermopile Thermal detector made up of many thermocouple junctions WMO...

Page 31: ...hermistor specifications YSI Thermistor 44031 Resistance versus Temperature in C CGR 4 Manual Page 31 Thermistor 10 kΩ 25ºC α β ln R γ ln R 3 1 273 15 α 1 03 10 3 β 2 38 10 4 γ 1 59 10 7 T Temperature T ºC Resistance R Ω ...

Page 32: ...pendix III Pt 100 specifications Pt 100 Resistance versus Temperature in ºC and ºF CGR 4 Manual Pt 100 100 Ω 0ºC α 3 9083 10 3 β 5 8019 10 7 α α2 4 β T R 100 1 2 β Temperature T ºC Resistance R Ω Page 32 ...

Page 33: ...on Centres World Radiation Centre The World Radiation Centre capable of pyrgeometer calibration is located at Physikalisch Meterologisches Observatorium Dorfstrasse 33 CH 7260 Davos Dorf Switzerland Website www pmodwrc ch CGR series Manual Page 33 ...

Page 34: ...n of their instruments every two years This can be done at the Kipp Zonen factory Here recalibration to the highest standards can be performed at low cost Recalibration can usually be performed within four weeks If required urgent recalibration can be accomplished in three weeks or less subject to scheduling restrictions Kipp Zonen will confirm the duration of recalibration at all times Please not...

Page 35: ... y reserva Passion for Precision Go to www kippzonen com for your local distributor or contact your local sales office HEAD OFFICE Kipp Zonen B V Delftechpark 36 2628 XH Delft P O Box 507 2600 AM Delft The Netherlands T 31 0 15 2755 210 F 31 0 15 2620 351 info kippzonen com Kipp Zonen Asia Pacific Pte Ltd 81 Clemenceau Avenue 04 15 16 UE Square Singapore 239917 T 65 0 6735 5033 F 65 0 6735 8019 ki...