Kipp & Zonen CMP 3 Instruction Manual

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Kipp & Zonen CMP 3 Instruction Manual Manual pdf 39 page image

.A.9 Zero offset type BProportionally to the ambient temperature the instrument temperature varies and causes thermal currents inside the instrument.This will cause an offset commonly called Zero Offset Type B. It is quantified in ISO 9060:1990 as the response in W/m² to a 5 K/hrchange in ambient temperature.A.10 Operating temperatureThe operating temperature range of the radiometer is determined by the physical properties of the individual parts. Within the specifiedtemperature range Kipp & Zonen radiometers can be operated safely. Outside this temperature range special precautions should betaken to prevent any physical damage or performance loss of the radiometer. Please contact your Kipp & Zonen representative forfurther information regarding operation in extreme temperature conditions.A.11 Field of viewThe field of view is defined as the unobstructed open viewing angle of a radiometer. ISO and WMO require that a pyranometerfor the measurement of global solar radiation has a field of view of 180 ° in all directions (i.e. a hemisphere). The inherent fieldof view of the instrument should not be confused with the clear field of view of the installation location.A.12 Directional responseRadiation incident on a flat horizontal surface originating from a point source with a defined zenith position (such as the sun)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 illustrated below. α is the zenith angle, where 0 ° is vertical and 90 ° is horizontal.Ideally a pyranometer has a directional response which is exactly the same as the cosine-law. However, in a pyranometer thedirectional response is influenced by the detector and by the quality, dimensions and construction of the dome(s). The maximumdeviation from the ideal cosine-response of the pyranometer is given up to 80 ° angle of incidence with respect to 1000 W/m²irradiance at normal incidence (0 ° zenith angle).A.13 Maximum irradianceThe maximum irradiance is defined as the total irradiance level beyond which physical damage may occur to the instrument.A.14 Non-stabilityThis is the percentage change in sensitivity over a period of one year. This effect is mostly due to degradation by UV radiationof the black absorber coating on the thermopile surface.Kipp & Zonen recommends recalibration every two years. However, for quality assurance purposes some institutes, companies ornetworks may require more or less frequent recalibration. Please read the chapter on the calibration procedure for pyranometersfor more information.α = 45 ° α = 0 °39