Transmittance measurement system based on triple-junction solar cells

The degradation of solar cells' coatings in space environment will shorten space aircraft's fight life. So the research of the system which can measure the coatings transmittance's change is important. The transmittance measurement system was constructed by two triple-junction solar cells, one of which was covered with the glass sample and another was not. The triple-junction solar cells were used as detectors to measure solar flux. The photocurrent measurement circuits convert the photocurrent to analog volt, which will be multiplied and filtered. And the volt was translated to digital signal, which is transferred to the computer finally. The photocurrent signals of two triple-junction solar cells were acquired to calculate the overall transmittance in the solar cell responding spectrum, by using two channels comparing measurement method. The solar cells operation temperature was monitored by platinum-chip temperature sensors, in order to avoid measurement error which is induced by temperature change. The measurement relative error of system is about 0.1%, and the measurement uncertainty is less than 0.15%, which is proved by experiment.