Kipp & Zonen CSD1, Instruction Manual

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15
1.5 MEASUREMENT OF DIRECT RADIATION
An output representing the direct radiation is available. This signal is 0 V
when no direct radiation is present, and varies linearly with the irradiance.
The calibration is factory set at a level of 1 mV equivalent to 1W/m2.
Measuring this parameter can be useful because the information in the
sunshine duration signal is limited, only showing if this signal is above or
below a certain level.
Note: This signal is not a substitute for Pyranometer/Pyrheliometer
measurements and does not have the same level of accuracy.
1.6 USING THE HEATER
One of the major error sources in the sunshine duration measurement is the
obstruction of the light by water that is deposited on the instrument. This can
be caused by rain, dew, frost or snow, and can be greatly reduced by
heating the instrument.
CSD 1 has on-board heaters that can be used at two levels. The heaters are
simple high power resistors that deliver 1 or 10 Watts at the recommended
supply voltage of 12 VDC. Switching of the heating levels can be done
externally with a switch or by a thermostat system (not included).
The low level heating will keep dew away and heating at the high level will
melt snow and ice at an ambient temperature not lower than -15
°
C
It is recommended to use the heater only when this is strictly necessary. At
ambient temperatures of more than +10
°
C the heater could be conditionally
switched off. Also in order to save power, during the night it is suggested not
to use the heater.
1.7 CALIBRATION & QUALITY CONTROL
CSD 1 has 3 detectors that have exactly the same spectral and angular
characteristics. This will benefit the process of re calibration. At Kipp &
Zonen, the calibration is done against a reference that is traceable to a
broadband solar radiation measurement under clear sky conditions.