18
2.2.1
Specifications of the pyranometer
Pyranometers Specification
Unit
Value (All indicated values are absolute values)
Spectral range
nm
300 - 2800 (50% points)
Definition
Instrument sensitivity within a specific spectral range
Sensitivity
µV/ W/m
²
10 to 20
Definition
Calibration factor
Impedance
Ω
20 to 200, typically 50
Definition
Typical resistance measured at the output
Response time
s
< 18 (95% response)
Definition
Sensor response time
Non-linearity
%
< 1 (from 0 to 1000 W/m
2
irradiance)
Definition
Maximum deviation from the responsivity at 500 W/m
2
due to any
change of irradiance within the indicated range.
Temperature dependence of
sensitivity
%
N/S (- 40
°
C to -10
°
C)
< 4 (- 10
°
C to +40
°
C)
N/S (+40 ºC to +80 ºC)
Definition
Maximum error due to any change of instrument temperature within
the indicated temperature interval.
Tilt error
%
< 1
Definition
Maximum deviation from the responsivity when tilted at any angle
and at 1000 W/m
²
irradiance .
Zero offset A
W/m
²
< 15 (0 to -200 W/m
²
/ IR net irradiance)
Definition
Caused by cooling of the dome due to sky radiation
Zero offset B
W/m
²
< 3 (at 5 K/h temp. change)
< 1 (with CVF 4 installed)
Definition
Response to change in ambient temperature.
Field of view:
Upper detector
Lower detector
180º
150º (due to lower sun shield. To prevent illumination at low zenith
angles)
Definition
Sensor opening angle
Directional error
W/m
²
< 20 (angles up to 80
°
with 1000 W/m
²
beam radiation)
Definition
Combined zenith and azimuth error from 0°- 80
°
with 1000 W/m
²
beam radiation
