For VI curve measurement, different voltages are applied to the PV cell, each forcing its corresponding output current. The SMU provides a sweep measurement option forcing voltage on two leads and simultaneously measures current on the other two. The sweep measurement starts at zero volts (short circuit current) and linearly increases the voltage. It measures the current till the open circuit voltage is crossed. This way every applied voltage can be matched with the corresponding output current and the VI Curve can be interpolated.