Question about measuring array string current with a clamp-on DC ammeter

Re: Question about measuring array string current with a clamp-on DC ammeter

Cool. That's what I was hoping, but I wanted to be sure that the other strings in parallel would not influence the string I was taking measurements on. Thank you!

Dill wrote: »

you should just be able to put the cable feeding your combiner inside the 'loop' of the ammeter, which will show the current being produced by that string. Repeat for the other 6 strings and you've then tested them all.

Re: Question about measuring array string current with a clamp-on DC ammeter

BB. wrote: »

When using a DC current clamp meter, it measures the "sum" of the current through the "loop"/Clamp... I.e., if you place one wire in the clamp, it will be the current in the wire. If you have the + and - leads in the current clamp (say +/- leads from one panel), the sum of current will be zero (note, DC clamp meters will have a +/- polarity on the LCD display, showing the direction of current flow).

-Bill

I understand Bill. I pulled out my trusty clamp-on ammeter yesterday and attached the clamp to the + side of the first string....only to realize that I only had an A/C current clamp meter!

So I ordered a DC clamp-on ammeter. From a previous post, I saw that zeroing the meter is crucial, so I'll make sure I do it right when it arrives.

I realize that if the load isn't high enough, the output of panels may be reduced. However, with "sell" enabled, I should be maximizing the PV output at all times (hopefully!). I just wanted to compare strings to ensure the panels are running properly.

If I wanted the test the string's max shorted current, is there a possibility of damaging the panels if I connected the + and - wires of the string? I would cover the panels first before connecting or disconnecting the wires.

-Dusty

Re: Question about measuring array string current with a clamp-on DC ammeter

BB. wrote: »

In theory, if the panels are properly designed and constructed--No problem (other than if you do this with MCx connectors, the arcing can very easily damage the contacts). So, I would suggest covering the panels before making/breaking short circuit connections.

In practice, I would only short circuit for a minimum amount of time. Panels can get hot from I²R heating and reduce future life. (should not be a problem, but from other posts, vendors years ago made warnings about shorting PV panels as part of an electrical protection system--so, even the vendors are not really standing behind their products--this was probably a decade or more ago from what I have read).

-Bill

Thanks Bill. It just seemed like a better way to compare panel output, since the readings could vary quite a bit (especially if the SCC is hunting) with the panels connected.

-Dusty