New ISO 9060:2018 Pyranometer Classifications
Apogee Instruments Pyranometers Meet New Class C Standard
With the release of the new ISO-9060:2018 pyranometer classifications, ISO did away with the old, confusing standards and has now grouped all
pyranometers into three new categories: A, B, and C. With this, Apogee’s pyranometers are all ranked in the C Classification, but not all C Classpyranometers are created equal. For example, the Apogee SP-510 thermopile sensor is only negligibly different than a Class B. The ISO standards are listed
below, along with the Apogee pyranometer specifications.

Apogee ModelsISO 9060:2018(E) Pyranometer Classification List
Parameter
A

Response timeA
(Secondary standard)

B(First class)C(Second class)

Apogee SP-510
Thermopile

Apogee SP-110
Silicon-cell< 10 s< 20 s< 30 s

0.5 s*< 0.001 s*
N/A

B

Zero offset A± 7 W/m²± 15 W/m²± 30 W/m²± 8 W/m²;± 30 W/m² (heated)

B

Zero offset B± 2 W/m²± 4 W/m²± 8 W/m²± 5 W/m²

N/A

B

Zero offset C± 10 W/m²± 21 W/m²

41 W/m²± 13 W/m²;± 35 W/m² (heated)

N/A

C1Non-stability± 0.8 %

± 1.5 %

±3%±2%±2%C2Nonlinearity± 0.5 %

±1%

±3%

±1%

±1%

C3

Directional response± 10 W/m²± 20 W/m²± 30 W/m²± 25 W/m²± 30 W/m²

C4Spectral error± 0.5 %

±1%

±5%

±2%

±4%

C5Temperature response

±1%

±2%

±4%±4%±3%

C6

Tilt response± 0.5 %

±2%

±5%

±1%

N/A

C7

Additional signal processing errors± 2 W/m²± 5 W/m²± 10 W/m²

N/AN/A* Pyranometers with response times < 0.5 seconds are classified as “fast response” pyranometers.
30302020100

www.apogeeinstruments.com

100-10-10-20-20-30

0.0

0.2

0.4

0.6

0.8

1.0

SWi / SWic

1.2

1.4

-30

0.0

0.2

0.4

0.6

0.8

SWi / SWic

1.0

1.2

1.4

Differences [%] of an SP-510 thermopile pyranometer and an SP-110
silicon-cell from the mean of the four secondary standard (reference)pyranometers as a function of cloudiness. Black lines are bin averages. The
variable SWi / SWic is the ratio of measured global shortwave irradiance[W m⁻²] to clear sky global shortwave irradiance [W m⁻²] calculated froma model, and serves as a cloudiness index. Values of SWi / SWic near one
indicate clear sky and values near zero indicate overcast sky. The predicted
error values listed on each graph were calculated from the spectral
response for each sensor and a solar spectrum for overcast conditions,assuming the pyranometers were calibrated under clear sky conditions.
30

20

Difference from Reference [%]• Response time: time for 95 % response• Zero offset A: response to -200 W/m² net thermal radiation• Zero offset B: response to 5° C per hour change in ambient temperature• Zero offset C: total zero offset including zero offset A, zero offset B, andother sources• Non-stability: percentage change in responsivity per year
• Nonlinearity: percentage deviation from the responsivity at 500 W/m²
due to the change in irradiance within 100 W/m² to 1000 W/m²
• Directional response (for beam radiation): the range of errors caused byassuming that the normal incidence responsivity is valid for all directions
when measuring from any direction (with an incidence angle of up to 90°
or even from below the sensor) a beam radiation whose normal
incidence irradiance is 1000 W/m²
• Spectral error: maximum spectral error observed for a set of global
horizontal irradiance clear sky spectra defined in the ISO 9060:2018(E)document• Temperature response: percentage deviation due to the change inambient temperature within the interval from -10° C to 40° C relative tothe signal at 20° C• Tilt response: percentage deviation from the responsivity at 0° tilt
(horizontal) due to change in tilt from 0° to 180° at 1000 W/m²
irradianceDifference from Reference [%]SP-110 silicon-cell
Difference from Reference [%]SP-510 thermopile

100-10-20-300102030405060

Solar Zenith Angle [°]708090Differences [%] of an SP-510
thermopile from the mean of four
secondary standard (reference)pyranometers as a function of solar
zenith angle. Black lines are binaverages for AM and PM. The
green and orange lines are
estimates of the specifications forfirst class (± 20 W m⁻²) and secondclass (± 30 W m⁻²) pyranometers,
respectively, as a function of solar
zenith angle.