Kipp&Zonen CHP 1 Pyrheliometer - Manual (Page 16)

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8 RECALIBRATION
Radiometer sensitivity changes with time and with exposure to radiation. Periodic calibration every two years is
advised.
Accurate calibrations can be done outdoors under clear conditions by comparison with a reference pyrheliometer.
Many national or regional weather services have calibration facilities. Their standard pyrheliometer is compared with
the World Radiometric Reference at Davos, Switzerland. This embodies several absolute cavity (black body)
pyrheliometers. Information about regional calibration centres can be found in appendix V.
9 FREQUENTLY ASKED QUESTIONS
The most frequently asked questions are listed in the FAQ section of our website at
www.kippzonen.com
10 TROUBLE SHOOTING
The following contains a procedure for checking the instrument in case it appears that it does not function as it
should.
Output signal fails or shows improbable results:
• Check the wires are properly connected to the readout equipment.
• Check the instrument location. Are there any obstructions that cast a shadow on the window by blocking
the direct sun during some part of the day?
• Check the window, it should be clear and clean. If water is deposited on the inside, please change the
desiccant. If too 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.
• If water or ice is deposited on the window, clean it. Probably water droplets will evaporate in less than one
hour under sunlight.
Any visible damage or malfunction should be reported to your distributor, who will suggest appropriate action.