Solving a Multimeter Problem with 10k Internal Resistance

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Discussion Overview

The discussion revolves around a problem involving a multimeter with a specified internal resistance and its interaction with a voltage source. Participants explore the implications of the multimeter's resistance on its readings when connected to a source with its own internal resistance. The scope includes conceptual understanding of multimeter operation and circuit behavior.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant presents a problem involving a 20,000 ohms per volt multimeter connected to a 1 volt source with a 10k internal resistance, seeking help to understand the setup.
  • Another participant explains that the meter's specification indicates it will load the circuit with a resistance of 200,000 ohms when in the 10 volt range, suggesting a series circuit analysis.
  • A third participant describes the circuit as having a 10k ohm resistance in series with a 20k ohm resistance, proposing to use Ohm's law to find the voltmeter's reading.
  • One participant questions the relationship between high resistance and sensitivity, expressing confusion about why higher resistance does not imply lower sensitivity in this context.
  • Another participant clarifies that a high resistance in a meter results in less current drawn from the circuit, which is beneficial for accurate measurements.

Areas of Agreement / Disagreement

Participants express differing levels of understanding regarding the implications of the multimeter's resistance on its readings. There is no consensus on the conceptual clarity of the relationship between resistance and sensitivity.

Contextual Notes

Some assumptions about circuit behavior and the definitions of sensitivity and resistance may not be fully articulated, leading to potential misunderstandings in the discussion.

Who May Find This Useful

Individuals interested in electronics, particularly those learning about multimeter operation and circuit analysis, may find this discussion relevant.

scientifico
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Hello, I'm trying to learn some electronics by myself but it's quite difficult, now I'm studying the multimeters and a problem says

What will a 20000Ω/V meter read on its 1 volt scale, when attached to a 1 volt source with an internal resistance of 10k?

Can you set up this problem for me because I didn't yet understood well the argument. Thank you!
 
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Analog meters have an ohms per volt spec. This means that if the meter a 20,000 ohms per volt spec and has a 10 volt range that means that the load the probes will put on a circuit while in the 10 volt range would be 200,000 ohms. So do the math figuring a series circuit of 10K ohms with 200K ohms and a 1 volt source.
 
It is equivalent to having the voltmeter in series with a resistance R1 of 10k and another R2 of 20k.

Use V = IR to find V2 which is the reading of the voltmeter.
 
But doesn't an high resistance mean a lower sensibility (because it "resist" to more electrons)? Instead why it's the opposite here?
 
scientifico said:
But doesn't an high resistance mean a lower sensibility (because it "resist" to more electrons)? Instead why it's the opposite here?

I don't understand what you just said, but here's the thing: high resistance in a meter means the meter will have less effect on the circuit that it is measuring because it will draw less current out of it. That's a good thing.
 

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