Kippzonen CFR Calibration Facility Bedienungsanleitung PDF herunterladen (Seite 13)

CFR manual

There are several procedures for transferring calibration values from a narrow field of view instrument

(pyrheliometer) to a wide field of view instrument (pyranometer). For example the direct component of the

solar radiation can be eliminated temporarily from the pyranometer by shading the whole outer dome of the

instrument with a disk. However, there is no thermal equilibrium with this method and some models of

pyranometer show significant zero-offset drift.

An alternative procedure maintains the test pyranometer in its normal operating condition. This 'component

sum' method involves measuring the direct component of the solar radiation with a pyrheliometer and the

diffuse component with a shaded pyranometer, and adding together the two values to obtain the global

radiation. As, during a clear day, the diffuse radiation is only about 10% of the global radiation, the

sensitivity of the second pyranometer does not need to be known very accurately. Both procedures are

suitable to obtain a working standard pyranometer. This method is extensively described in international

standard ISO 9846.

Transfer from the working standard pyranometer to other pyranometers can be done in sunlight. The

pyranometers must be mounted side by side so that each views the same sky dome. It is desirable to

integrate, or average, the outputs over a period of time and then compute the calibration constants on the

basis of these averages. This reduces the errors due to changing parameters during the day.

Transfer from a working standard pyranometer in the laboratory is only reliable when both pyranometers

are of the same construction and have similar optical characteristics. Kipp & Zonen can recalibrate

pyranometers according to this method.

2.3.3 Spare Parts Specification

This section provides the article numbers for ordering spare parts for the Calibration Facility.

Part Description Part No.

Lamp Housing : 230 VAC / 50Hz Version 2654116

: 115 VAC / 60Hz Version 2654117

Bulb (115 & 230 VAC) : Philips CDM-T 150 W / 942 2603864

Lamp stabilizer (230 VAC) : MCB Industries , Model 250 VA / 50Hz 2681060

Voltage measurement device : Keithley Instruments, model 2000 4902212

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Kippzonen CFR Calibration Facility Bedienungsanleitung Seite 13