Today we’re going to capture an IV curve of
a solar panel using our new N6784A SMU module. It’s a four-quadrant power supply and can be
used in the 1U high compact system mainframe or it could be used in a
bench-friendly DC power analyzer. For our demonstration today, we’ve installed
the SMU module into channel one of the DC power analyzer, and we’re using
channel two to power our LED light source. Our LED light source is bright enough to create
some photovoltaic energy in our solar panel, which will use the SMU module
to capture both the voltage and current. We’ve written a simple demonstration program
to plot our IV curve. We start at zero volts and we make a current measurement from the
We increase the voltage and make a current measurement. We continue to do that until
we step all the way through our IV curve. From our IV curve, we can make several important
measurements. We can capture the short-circuit current, which is the true short-circuit current.
If we tried to make the same measurement with a multimeter, it would be a little bit low
because of the burden voltage of the multimeter. We can also measure the open circuit voltage of
the solar panel, we can calculate the fill factor, as well as locate the max power point.
Now, if we dim the light source, we can make another IV trace with lower
illumination, and we can repeat this. Lower the light source and capture a curve. With our family of curves, you can see with
lower levels of illumination, it really affects the first part of the IV curve more
than the second half of the IV curve.
This is common with solar panels. Being that this is a four-quadrant power supply,
we can actually extend our measurements into the adjacent quadrants. So we’ve started
a new IV curve into the adjacent quadrants. So above this axis the SMU is sinking current,
below this axis we’re sourcing current. Likewise, on this axis we’re sourcing
a positive voltage and on this side of the axis we’re sourcing a negative voltage.
So in this particular example, we started with a negative voltage, we slightly
increase it, measure the current and repeat that until we go all the way through our IV curve.
Once again, if I dim our light source, we
can see that we’re tracing the IV curve through three different quadrants of the power
supply. The power supply is able to make these transitions from a negative voltage to
a positive voltage, from sinking current to sourcing current glitch free. As you can see, it’s easy to capture an
IV curve from a solar panel using our new N6784A general purpose module..