Solar Cell Current increases as Resistance increases Problem

AI Thread Summary
The discussion centers on a user experiencing unexpected results when measuring current from solar cells with varying resistances. They noted that increasing resistance led to higher amperage readings, which contradicted expected behavior. The issue was identified as a misconfiguration in the multimeter connections, specifically using parallel connections for amperage measurements instead of the required series connections. Once the user corrected the setup, they successfully obtained accurate data. This highlights the importance of proper multimeter usage in electrical measurements.
PVJ2016
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Hi everyone, so I'm trying to achieve IV curves based on how this website had done below:
http://www.voltaicsystems.com/blog/solar-charger-tutorial-part-2/

But whenever I increase the resistance, the amperage increases rather than decreases! For example, when I use a 500 ohm resistor the amperage is 500 uA but when I use a 3.6 ohm resistor the amperage is 30 uA. The voltage seems to increase when more resistance is applied so nothing wrong there... could this be a problem with my multimeter? I tried this with two different solar cells and both have the same issue. BTW, I am a total noob when it comes to this stuff so anything is much appreaciated :)

also, this is how I am hooking up the resistors:
http://www.mtmscientific.com/solar4.jpg
 
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For amperage measurements you want the multimeter connected in series, not in parallel. What's happening here is that some of the current is flowing through the resistor and some of it is flowing through the multimeter, and the multimeter is reporting only the fraction that is flowing through it. Google for "ammeter parallel" for more on this.

For the voltage measurement, the parallel connection is fine; you're comparing the voltage at two points so you just need a probe at each point. No noticeable current flows through a multimeter doing a voltage measurement.
 
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Nugatory said:
For amperage measurements you want the multimeter connected in series, not in parallel. What's happening here is that some of the current is flowing through the resistor and some of it is flowing through the multimeter, and the multimeter is reporting only the fraction that is flowing through it. Google for "ammeter parallel" for more on this.

For the voltage measurement, the parallel connection is fine; you're comparing the voltage at two points so you just need a probe at each point. No noticeable current flows through a multimeter doing a voltage measurement.
 
Thank you so much! I just did what you said and it worked :) Now I can finally get some data!
 
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