Hello there, I have a question. If I want to measure the resistance (Ri) of my power supply with a value of 0.5 Ohm, should I use the method where an ammeter is connected first and then a voltmeter? Additionally, can someone explain what causes deviation in this measurement method?

 

Hello there, I have a question.

Hello.

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Real meters will differ from ideal meters.
You need to take into account the properties of real meters.

 

Real meters will differ from ideal meters.
You need to take into account the properties of real meters.

Yes, I know that but I cant invent which methode should I use and why.

 

Think about the internal resistance of each meter.
Which one is significant enough to make a difference?
What should you measure in order to achieve your objectives?

 

Think about the internal resistance of each meter.
Which one is significant enough to make a difference?
What should you measure in order to achieve your objectives?

I know that in this method, the V meter also measures the Ri of the Ammeter, which is very small. However, I'm unsure which method is better for measuring small Ri, and I'm also wondering how Ri affects the measurement.

 

I know that in this method, the V meter also measures the Ri of the Ammeter, which is very small. However, I'm unsure which method is better for measuring small Ri, and I'm also wondering how Ri affects the measurement.

There are not two methods. There is only one method.
I will give you one hint.
The voltmeter has high internal resistance. It does not interfere with the measurement. Connect it and leave it connected. It measures voltage. It does not measure Ri.

 

There are not two methods. There is only one method.

That's not always true, although it may be in this case.

The best method depends upon the impedances of the meters.
You would need to calculate the power supply impedance with both configurations to determine which gives the least error.

The voltmeter first will cause the supply current to be slightly more than the measured current.
With the voltmeter second, the measured voltage will be slightly less than the power supply due to the ammeter internal resistance.