- #1
BlackHole213
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When using a multimeter, how come the values for the current and voltage fluctuate?
Understanding Fluctuations in Multimeter Readings
- Thread starter BlackHole213
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In summary, the conversation discusses the issue of fluctuating values for current and voltage when using a multimeter. The possible causes mentioned are a defective multimeter or actual fluctuations in the current and voltage. To troubleshoot, the suggestion is to check the multimeter by reading the voltage and current of a battery-operated device. It is also mentioned that fluctuations are normal in measurements and can be used to estimate uncertainty. It is advised to refer to the user's manual for more information on uncertainties.
- #2
Bobbywhy
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1. The multimeter is defective, or
2. The current and the voltage really are fluctuating.
I suggest you check your multimeter by reading the voltage and current of a battery-operated device. The voltage and current should not fluctuate.
2. The current and the voltage really are fluctuating.
I suggest you check your multimeter by reading the voltage and current of a battery-operated device. The voltage and current should not fluctuate.
- #3
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orBobbywhy said:
3. The batteries in the multimeter need replacing.
What are you measuring? What is the value of the voltage or current you are reading, and by how much is it fluctuating? That information might help us narrow down the cause.BlackHole213 said:
- #4
BlackHole213
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I got a voltage of about 6.692V. The digit after the 2 was fluctuating between 2 and 4. For the current, I got 1.236 mA with a similar fluctuation right after the 6. My assignment was to verify Kirchoff's current and voltage laws. Only a few of the calculations actually equal zero. The majority are off by a few milivolts or microamps. I am trying to account for the non-zero values in my discussion.
- #5
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Those appear to be real -- and very small -- fluctuations. Your readings are stable to 4 significant figures, it doesn't get much better than that! 
(At least in a student lab setting.)
As for the cause, it could have been the voltage source, or it could be the meter itself. In hindsight, it might have been good to measure the power supply voltage directly (with the circuit connected to it), and see what level of fluctuations were there.
At any rate, you can use the fluctuations to estimate the uncertainty in the measurements, and add a digit for the meter possible being off. As long as the loop voltage ±uncertainty contains zero, you are fine.
(At least in a student lab setting.)As for the cause, it could have been the voltage source, or it could be the meter itself. In hindsight, it might have been good to measure the power supply voltage directly (with the circuit connected to it), and see what level of fluctuations were there.
At any rate, you can use the fluctuations to estimate the uncertainty in the measurements, and add a digit for the meter possible being off. As long as the loop voltage ±uncertainty contains zero, you are fine.
- #6
Gordianus
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Welcome to the real world where measurements do fluctuate (I think the multimeter is working well).
The last digit of any multimeter should be regarded with suspicion.
I strongly suggest reading the user's manual as regards uncertainties.
The last digit of any multimeter should be regarded with suspicion.
I strongly suggest reading the user's manual as regards uncertainties.
- #7
cmb
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BlackHole213 said:
Just PM me if you want to swap your multimeter for one of my 3 digit meters - your problem will then disappear!
1. How do I change the units on my multimeter?
To change the units on your multimeter, you will need to locate the unit button or dial on your device. This is typically labeled as "Units" or has different symbols for each unit of measurement. Press or turn the button or dial to select the desired unit.
2. Can I manually input a specific value on my multimeter?
Yes, some multimeters have a feature that allows you to manually input a specific value. This is useful when you need to measure a value that is not provided on the pre-set settings. Look for a "Manual Range" button or setting on your multimeter and follow the instructions to enter your desired value.
3. Why is my multimeter showing a negative value?
If your multimeter is showing a negative value, it is most likely because you have the probes connected in reverse. Make sure the positive probe is connected to the positive terminal and the negative probe is connected to the negative terminal. If the problem persists, check the batteries and make sure they are not low or replace them.
4. How do I reset my multimeter to the default settings?
The process for resetting a multimeter to its default settings varies depending on the model. Some may have a "Reset" button, while others may require you to remove the batteries and wait a few minutes before reinserting them. Refer to your multimeter's instruction manual for specific steps on how to reset it.
5. Can I use my multimeter to measure AC and DC voltage?
Yes, most multimeters have the capability to measure both AC and DC voltage. However, it is important to select the correct setting for the type of voltage you are measuring. Look for symbols that indicate AC or DC voltage on your multimeter and make sure the probes are connected to the correct terminals before taking a reading.
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