4 Making Measurements
4-5
Turn on SolSensor
Press and release the LED pushbutton. SolSensor powers up and starts looking for the
wireless network. The LED blinks on and off while searching, and turns steady ON after
it connects.
The original SolSensor connects to the wireless USB adapter plugged into your PC or
communicates indirectly using the I-V Unit as a relay station.
The SolSensor 300xx (for the PVA-1500xx) communicates only through the I-V Unit (as
a relay station) to the PC.
Prepare the PV source circuits for measurement
If measuring strings at a combiner box, it is safest practice to first turn off the inverter.
Then open the DC disconnect to electrically isolate the combiner from the inverter and
the rest of the array. Then lift all of the touch-safe string fuses in the combiner box.
If measuring strings at an inverter, shut down the inverter and lift all of the string fuses.
You may be able to use the fuse clips as test points to attach the test lead alligator clip. If
there is no convenient way to clip in the ‘common’ lead, you may be able to insert a
short-insulated wire pigtail in a spare terminal, and connect the alligator clip to the
pigtail.
Are you measuring strings in parallel?
If you are measuring multiple strings in parallel, be sure that the maximum PV current
you plan to measure is always less than the specified maximum current of the I-V
Measurement Unit. To estimate the maximum current the paralleled strings will produce,
measure a single string in full sun, and multiply the measured short circuit current Isc by
the number of strings you plan to measure in parallel. Be aware that the maximum total
current will increase when the sun is more directly in front of the array, and that in the
span of a few seconds, cloud edge effects can increase total current more than 25% above
normal clear-sky conditions.
Are you measuring high-efficiency modules?
High-efficiency modules produce a short but intense pulse of current at the start of every
I-V curve measurement. The I-V Measurement Unit is designed to tolerate that intense
pulse from a single string of high-efficiency modules, but measuring two or more high-
efficiency strings or modules in parallel may damage the instrument.
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