IEC 60904-9:2020 © IEC 2020
– 11 –
– For a two channel I-V measurement (voltage, current) with a pulsed or steady-state solar simulator,
irradiance shall be measured before and after I-V measurement. The LTI value shall be
calculated from
these two irradiance values. The LTI value may depend on the I-V data acquisition time and the stability of
the light source. The maximum averaging interval for irradiance shall correspond
to the time interval
between I-V data points.
– For irradiation exposure LTI shall be verified for the specifications (time period, data recording interval for
irradiance) given by the supplier. If such information is not available LTI shall be related to at least 100
irradiance values, with a minimum of one
data point per hour, taken at equal intervals over the exposure
period.
Note 2 to entry:
Irradiance corrections, such as those of IEC 60891, are often used to minimize the effects of
irradiance fluctuations on PV module output power measurements. The uncertainty related to
irradiance correction
will depend on the difference “measured irradiance –target irradiance” and the precision of relevant I-V correction
parameters of the PV device. For other applications, the use of such corrections should be
considered together
with requirements for solar simulator temporal instability.
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