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Posts: 1
Reply with quote  #1 
Admin edit to add a note from PVJ2016:  
I'm having issues with a small solar panel, one of those DIY ones. I'm trying to measure out the solar panels amperage and voltage to obtain a volts vs amps IV curve graph

Hi everyone, I have a little dilemma. I am trying to achieve IV curves and for some reason my Amperage drops from a 100 ohm to 3.6 ohm resistor ( 100 ohm = 500 ua, 3.6 ohm =30 ua), and so when I increase my ohms value the current increases [confused]. Should it be the other way around? My voltage seems to follow the basic standard that when the ohms value is lower, the voltage is lower. I'm assuming its a problem with the multimeter.

This is my first time attempting IV curves so an advice would be appreciated.


Posts: 139
Reply with quote  #2 
As you can see from the graph, when the resistance is zero, the panel will produce 0 volts, but it's max possible current. As the resistance increases towards infinity (open circuit) the voltage will increase and current will drop.

So yes, your measurements should be the other way around!  What current/voltage do you measure with the panel's terminals shorted via the meter, and open circuited?



Posts: 139
Reply with quote  #3 
And, here is a link to a teacher's manual for a course helping  students measure and evaluate PV IV power curves. Page 13 has the circuit and method, are you wiring your voltmeter and current meter this way?

Instead of using  variable resistor use your two resistors in the circuit, what do you get?


Posts: 4
Reply with quote  #4 
First learn some basic OHMs law and really learn how to use your multimeter and ammeter , remember if you are measuring current or amperage the meter has to be it SERIES with the load and if you want to measure voltage the meter needs to be in parallel with the circuit or load , pos to pos and neg to neg !!!  This may sound simple but just learning some small basic steps will put you miles ahead when working on your project !!! Find a course on AC/DC theory and one or a book on using your meter it is an invaluable tool , I normally use my scope and meters together to find faults or check circuit configurations , for me Solar is very simple stuff but a very interesting and enjoyable field , but if you are just learning it can be very foreign and abstract !!! I have a Degree in Industrial Technology and a Minor in Electronics with 34 years experience in the field !!
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