Measurement of PV charachteristics of Solar Panel

[Codyzded31]

Hallo All

I am trying to measure the Current voltage characteristics of 4 solar panels. Its just that when I connect  solar panel 1 to one channel and solar panel2 to channel 2 and reverse the connections I dont read the same values. I am not able to trouble shoot this problem. Any help is much appreciated. 

[GerdW]

Hi Codyzded,

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@Codyzded31 wrote:

I am trying to measure the Current voltage characteristics of 4 solar panels. Its just that when I connect  solar panel 1 to one channel and solar panel2 to channel 2 and reverse the connections I dont read the same values. I am not able to trouble shoot this problem.

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• So you do some measurements with some unknown sensors, with some unknown DAQ hardware and (probably) some LabVIEW program(s) which you decided not to attach for inspection. Mind to share more information on your problem?
• You do measurements for 4 channels, but you want to measure 8 different values (4 voltages, 4 currents)!? How does that fit together?
• You do some measurements, but you don't get "the same values" when "reversing the connections"!? What do you define as "the same value" and how do you "reverse some connections"?

[Codyzded31]

Hi Gerd,

I am using NI 9205. I have totally 13 channels ( Voltage: 4, Current:4, Temperature: 4 and speed:1 ). I have still not had the oppurtunity to measure with voltage and current of all 4 panels( waiting for a part delivery). I have measured with one panel current, voltage and temperature. Found the values to be ok. Current and voltage confirmed with multimeter. Temperature used a solder gun with known input temperature and showed correct results. 

Please let me explain: So first I connected channel one to solar panel one and channel two to solar panel two ( differential measurement). Then I put solar panel two to channel one and solar panel 1 to channel 2. This is what I meant by reversing. I have also only isolated both these channels that means I am not connecting and reading anything else on the DAQ. Just two voltages from two solar panels. I tried adding a dummy channel but this doesnt solve my problem.

Any more help will be appreciated. Thank you.

[GerdW]

Hi Codyzded,

so you are using a NI9205 module?

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@Codyzded31 wrote:

So first I connected channel one to solar panel one and channel two to solar panel two ( differential measurement). Then I put solar panel two to channel one and solar panel 1 to channel 2. This is what I meant by reversing. 

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So we are talking about pins AI0, AI1, AI8 and AI9? And you switched all of them?

[Codyzded31]

Yes. I do also want to tell you that the DAQ and the source are connected to the same ground. But the voltages I am getting are not from the same ground. I mean I have 3 megaohms in series ( 1 X 3 times) and i am taking the voltage reading from across one of the resistor. But solar panel is connected across 3 mega ohms. The negative of the solar panel, one end of the 3 megaohm are all connected to the common ground. 

I also want to mention I have no resistors for bias currents. But I am not sure if it is a grounding Problem..

Please want to be clear: A0 and A8 : solar panel 1 : A1 & A9 Solar panel 2. 

2nd try: A1 & A9: solar Panel 1; A0 & A8 : solar panel 2.

sorry for the late reply only have 2 posts per day as new user..

[Codyzded31]

Hallo All

Just an update on my problem. I am measuring only 4 voltages of  4 solar panels. I have connected the first 4 channels for solar panel 1-4. I got a set of values and then I changed only solar panel one and solar panel 4 to each others channels respectively. I dont get the exact same set of values. Any help will be appreciated.

[RTSLVU]

Your description of your electrical connections is confusing, please post a detailed schematic diagram of all your connections in both the configuration that worked and the configuration that failed.

[Frozen]

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@Codyzded31 wrote:

I do also want to tell you that the DAQ and the source are connected to the same ground. But the voltages I am getting are not from the same ground. I mean I have 3 megaohms in series ( 1 X 3 times) and i am taking the voltage reading from across one of the resistor. But solar panel is connected across 3 mega ohms. The negative of the solar panel, one end of the 3 megaohm are all connected to the common ground. 

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I agree with RTSLVU, your verbal description is not making sense. My first guess is that the statement I highlighted is probably the reason you are not getting the same values. But again, please provide a detailed electrical schematic.

[Codyzded31]

Hallo All

Please find the figure below attached. The first and second case the values must match but they dont.

[RTSLVU]

That is not a detailed schematic of your electrical connections.

I need to see how your entire system is wired, including the three one meg ohm resistors in both configurations!