Kipp & Zonen CM 11 Instruction Manual page 37

applies enough force. It is normal that you have to use two hands to
open and close it.
It is very difficult to make the pyranometers hermetically sealed. The only way
to do this properly is to put the inside of the instrument under pressure. (>
1.0 Bar), but this has to be checked at yearly intervals.
So, due to pressure differences inside and outside the instrument there will
always be some exchange of (humid) air.
In some networks, the exposed dome of the pyranometer is ventilated
continuously by a blower to keep the dome above dew point temperature. The
need for heating strongly depends upon local climatological circumstances.
Generally heating is advised during cold seasons when frost and dew can be
expected.
The ventilation also decreases the sensitivity to thermal radiation (zero offset
type A) by a factor of 2 or more.
The Kipp & Zonen CV 2 ventilation unit is specially designed for accurate
unattended operation under most weather conditions.
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MAINTENANCE