Hello...I am measuring voltage change in a solar cell with temperature change. I also need to measure open circuit current. The voltage is fine, however, I'm not sure if I'm reading the current correctly. Over the range of the temperature change (about 40*f to 76*f) I don't see any real change in current. Is this correct or am I using the multi meter wrong?
Thanks...Mike
current in a solar cell
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AeroSE
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Re: current in a solar cell
Hi MikeV,
This is a very interesting experiment. In order to answer your question about measuring current, I need a little more information from you. Can you describe how you have the multi-meter attached to your circuit? Additionally, what settings do you have the multi-meter set to when measuring current?
To measure voltage, we place the multi-meter in parallel with the circuit. This allows your circuit to not be disrupted by the multi-meter.
To measure current, we place the multi-meter in line (referred to as "in series") with the circuit. The multi-meter essentially becomes a component within your circuit. This forces all of the current flow through the multi-meter, so that it may take the measurement.
Make sure your multi-meter probes are fused to protect your multi-meter. Hope this helps.
-AeroSE
This is a very interesting experiment. In order to answer your question about measuring current, I need a little more information from you. Can you describe how you have the multi-meter attached to your circuit? Additionally, what settings do you have the multi-meter set to when measuring current?
To measure voltage, we place the multi-meter in parallel with the circuit. This allows your circuit to not be disrupted by the multi-meter.
To measure current, we place the multi-meter in line (referred to as "in series") with the circuit. The multi-meter essentially becomes a component within your circuit. This forces all of the current flow through the multi-meter, so that it may take the measurement.
Make sure your multi-meter probes are fused to protect your multi-meter. Hope this helps.
-AeroSE
Re: current in a solar cell
Thank you, AeroSE. I have the multimeter attached to the solar cell by connecting the two leads to the same leads on the solar cell. It looks like it is in parallel when I google it, but since I am reading both voltage and current from the same voltmeter, how can it also be in series? All I do is flip the switch from volts to amps.
I put the light source on the cell and put a heat pad underneath to get warm temperatures (Ice later for cold). Then when it changes every two degrees F, I flip from voltage to current and write down the values. The voltage is pretty steady - getting higher as the temperature drops. But my current is up and down. I don't see any good pattern. Eventually it drops as the temperature drops but it is up and down most of the time.
Is it correct that the current should drop as temperature drops?
Thank you again, Mike V.
I put the light source on the cell and put a heat pad underneath to get warm temperatures (Ice later for cold). Then when it changes every two degrees F, I flip from voltage to current and write down the values. The voltage is pretty steady - getting higher as the temperature drops. But my current is up and down. I don't see any good pattern. Eventually it drops as the temperature drops but it is up and down most of the time.
Is it correct that the current should drop as temperature drops?
Thank you again, Mike V.
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AeroSE
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Re: current in a solar cell
Hi MikeV,
If I understand your setup, you are attempting to measure both current and voltage with the voltmeter in parallel. This setup is appropriate for measuring voltage but will not all for accurate current(amps) readings. I assume that you have a resistor in this circuit, thus allowing for the voltmeter to be attached in parallel.
To get an accurate current reading, attach the voltmeter between the solar cell and the resistor (this will now be in series), and switch the voltmeter to measure amps. If the reading appears as a negative, you just need to switch your leads, though the magnitude of the measurement should be the same. This should provide accurate and consistent current measurements.
Once you have your setup, you should have a clear indication of the impacts of temperature on current. Something you have not mentioned is how you are manipulating the temperature of the solar cell? Your method of temperature manipulation may also create noise in your experiment. My limited understanding of Solar Cells is that their efficiency decreases as temperature increases. So it would be an inverse relationship (temperature goes up, efficiency goes down).
Hope this helps,
AeroSE
If I understand your setup, you are attempting to measure both current and voltage with the voltmeter in parallel. This setup is appropriate for measuring voltage but will not all for accurate current(amps) readings. I assume that you have a resistor in this circuit, thus allowing for the voltmeter to be attached in parallel.
To get an accurate current reading, attach the voltmeter between the solar cell and the resistor (this will now be in series), and switch the voltmeter to measure amps. If the reading appears as a negative, you just need to switch your leads, though the magnitude of the measurement should be the same. This should provide accurate and consistent current measurements.
Once you have your setup, you should have a clear indication of the impacts of temperature on current. Something you have not mentioned is how you are manipulating the temperature of the solar cell? Your method of temperature manipulation may also create noise in your experiment. My limited understanding of Solar Cells is that their efficiency decreases as temperature increases. So it would be an inverse relationship (temperature goes up, efficiency goes down).
Hope this helps,
AeroSE
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bfinio
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Re: current in a solar cell
Hi MikeV and AeroSE,
Chiming in here - Mike, it sounds like your goal was to measure the open circuit voltage and short circuit current - in both cases meaning there is no load attached. That gives you the maximum possible voltage the solar cell can provide, and the maximum possible current it can provide, although under real use circumstances (when it is attached to a load, using a resistor like AeroSE suggested) both values would be lower. So, you should be able to do this as described without a resistor. In either case, the multimeter is the only other component in the circuit besides the solar cell - so it's in parallel when set to measure voltage (the multimeter effectively has infinite resistance, so it doesn't allow any current to flow through it, so the circuit is open), and it's in series when it's set to measure current (the multimeter effectively has zero resistance, so it allows a lot of current to flow through it, like a short circuit).
Unfortunately, we can't give specific advice without knowing more about your multimeter. Most multimeters have different dial settings for different sensitivity levels when measuring current (for example in the milli-amp or micro-amp range). If you aren't seeing a change you might want to try a higher sensitivity. Taking a look at our multimeter tutorial might help:
https://www.sciencebuddies.org/science- ... multimeter
The other possibility is that temperature doesn't actually affect current, at least not as much as it affects voltage. I don't know the answer here off the top of my head without doing more research. However, the electrical power delivered from your solar cell would still change in this case, because Power = Current x Voltage. Remember that in general with science projects - your results might not be what you expected, but that doesn't mean they're wrong!
As AeroSE mentioned there could also be sources of noise in your experiment - like temperature fluctuations or maybe changes in light levels, that could make the values change.
Hope that helps,
Ben
Chiming in here - Mike, it sounds like your goal was to measure the open circuit voltage and short circuit current - in both cases meaning there is no load attached. That gives you the maximum possible voltage the solar cell can provide, and the maximum possible current it can provide, although under real use circumstances (when it is attached to a load, using a resistor like AeroSE suggested) both values would be lower. So, you should be able to do this as described without a resistor. In either case, the multimeter is the only other component in the circuit besides the solar cell - so it's in parallel when set to measure voltage (the multimeter effectively has infinite resistance, so it doesn't allow any current to flow through it, so the circuit is open), and it's in series when it's set to measure current (the multimeter effectively has zero resistance, so it allows a lot of current to flow through it, like a short circuit).
Unfortunately, we can't give specific advice without knowing more about your multimeter. Most multimeters have different dial settings for different sensitivity levels when measuring current (for example in the milli-amp or micro-amp range). If you aren't seeing a change you might want to try a higher sensitivity. Taking a look at our multimeter tutorial might help:
https://www.sciencebuddies.org/science- ... multimeter
The other possibility is that temperature doesn't actually affect current, at least not as much as it affects voltage. I don't know the answer here off the top of my head without doing more research. However, the electrical power delivered from your solar cell would still change in this case, because Power = Current x Voltage. Remember that in general with science projects - your results might not be what you expected, but that doesn't mean they're wrong!
As AeroSE mentioned there could also be sources of noise in your experiment - like temperature fluctuations or maybe changes in light levels, that could make the values change.
Hope that helps,
Ben