Voltmeter Problem Homework: Is My Answer Correct?

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In summary, the AVOM meter would act as a better voltmeter compared to the DMM due to its higher meter resistance. This makes it more sensitive and less likely to disturb the circuit or draw excessive current. Additionally, the resistance ratio of the voltage divider circuit is not altered as much with a higher resistance voltmeter. Good quality moving coil multimeters have a resistance of 200 K on the 10 volt scale, while digital multimeters have a resistance of 10 MEGOHMs, making them less sensitive.
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Homework Statement



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The Attempt at a Solution



I think that the AVOM meter would act as a better voltmeter. This is because it has a higher meter resistance, meaning that it is more sensitive. Therefore, it will disturb the circuit as little as possible and it will draw less current to operate compared to the DMM.

Is my answer correct?
 
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  • #2
This is because it has a higher meter resistance...

Higher resistance is good, as when the meter is placed in parallel with the circuit, the very high parallel resistance will draw very low current, and thus not change the circuit operation in noticeable ways. Do some math with a simple circuit with a 1V source and a 1R resistance representing the circuit, and then put a 500MR resistance representing the meter in parallel and see how the current is split.

...meaning that it is more sensitive...

Do you mean that an AVOM gives more accurate readings than a DMM? Do you have an explanation or justification for this?

Therefore, it will disturb the circuit as little as possible...

I think this is in partnership with the first quote, though explaining 'disturb' shows a better understanding of the actual mechanics.

...and it will draw less current to operate compared to the DMM.

What power sources do AVOM and DMM use, and why does one draw less current to operate than the other?
 
  • #3
Zryn said:
Do you mean that an AVOM gives more accurate readings than a DMM? Do you have an explanation or justification for this?

I meant that an AVOM has a higher "ohm per volt" value.


Zryn said:
I think this is in partnership with the first quote, though explaining 'disturb' shows a better understanding of the actual mechanics.

Zryn said:
By "disturb" I meant that the AVOM meter will draw less current from the circuit.


What power sources do AVOM and DMM use, and why does one draw less current to operate than the other?

The DMM and AVOM used a DC power supply (this question is from a lab experiment). I think that the AVOM meter draws less current than the DMM because it has a higher resistance. More specifically, a voltmeter with a high resistance will not alter the resistance ratio of the voltage divider circuit as much.

So is my answer generally correct? Is it not specific enough? Thank you for your help.
 
  • #4
So is my answer generally correct? Is it not specific enough? Thank you for your help.

Yes it is generally correct.

I think that the AVOM meter draws less current than the DMM because it has a higher resistance. More specifically, a voltmeter with a high resistance will not alter the resistance ratio of the voltage divider circuit as much.

I like this one better than the original!
 
  • #5
Good quality moving coil multimeters have 50 µA movements and a sensitivity of 20000 ohms per volt.

So, for example, they have a resistance of 200 000 ohms on the 10 volt scale. That is 200 K.

To check this, if it was connected to 10 volts DC on this scale, the current in the moving coil would be 10 Volts / 200000 ohms or 50 µA.

Notice that your table indicates a resistance of 200 MEGOHMS for this scale. This is not correct.

If the multimeter had a range of 25 volts full scale, the resistance of the meter on this scale would be 500 K. Your table indicates 500 MEGOHMS, which is incorrect

Good quality digital multimeters have a resistance of 10 MEGOHMs which agrees with your table. Cheap ones have a resistance of only 1 MEGOHM.
 

1. How do I know if my voltmeter problem homework answer is correct?

There are a few ways to check if your answer is correct. First, you can refer to your class notes or textbook to see if you followed the correct steps and equations. You can also ask your teacher or classmates for clarification or to check your work. Additionally, you can use a different method or formula to solve the problem and compare the results.

2. What should I do if my voltmeter problem homework answer is different from my classmates?

If your answer is different from your classmates, it could be due to a simple calculation mistake or different assumptions made in the problem. It's always a good idea to double check your work and compare it with others to see if you made any errors. If you are still unsure, don't hesitate to ask your teacher for help.

3. Can I use a calculator for my voltmeter problem homework?

Yes, you can use a calculator for your voltmeter problem homework. In fact, it is recommended to use a calculator to avoid calculation errors. However, make sure you know how to use your calculator properly and understand the calculations it is performing.

4. How do I set up my voltmeter problem homework?

To set up your voltmeter problem homework, you will need to understand the given information and what is being asked in the problem. Make sure to identify the variables, units of measurement, and any relevant formulas. Then, follow the correct steps to solve the problem.

5. What are some common mistakes to avoid in voltmeter problem homework?

Some common mistakes to avoid in voltmeter problem homework include using the wrong formula, mixing up units of measurement, and not double checking your calculations. It's also important to carefully read the problem and make sure you understand what is being asked before attempting to solve it.

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