Read the manuel that came with your meter.

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SUMMARY

To obtain accurate readings of potential difference with voltmeters that have finite resistance, it is essential to understand the meter's internal resistance and its impact on the circuit. Older voltmeters had a resistance of approximately 20K ohms per volt, which could significantly affect circuit measurements. Modern electronic voltmeters utilize field-effect transistors, resulting in much higher internal resistance, thereby minimizing their influence on the circuit. Calculating the effect of the voltmeter's resistance is crucial for precise measurements.

PREREQUISITES
  • Understanding of voltmeter operation and internal resistance
  • Basic circuit theory and Ohm's Law
  • Familiarity with field-effect transistors (FETs)
  • Ability to perform resistance calculations
NEXT STEPS
  • Research the specifications and resistance values of different voltmeter models
  • Learn about the impact of internal resistance on circuit measurements
  • Study the principles of field-effect transistors and their applications in electronic devices
  • Explore advanced techniques for minimizing measurement errors in electrical circuits
USEFUL FOR

Electronics students, electrical engineers, and technicians who require accurate voltage measurements in their work or studies.

richard7893
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For voltmeters with a finite resistance placed in a circuit, What can be done to get a correect reading of potential difference? my teacher said you would have to place a resistor between the leads of the voltmeter to get a close to correct reading, but I am just not quite wrapping my head around this idea.
 
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It doesn't make sense to put a resistor across the meter (unless you mean a resistor already in the circuit).

There isn't much you can do other than to learn the resistance of the meter (often stated on the face of the meter) and do some calculations to see how it is affecting the circuit.

At one time this was a serious problem because Voltmeters had something like 20K ohms resistance per volt on the range used. However, electronic Voltmeters usually have much higher resistance due to a field affect transistor on the front end. If you have a modern meter it is unlikely that its resistance is affecting a circuit significantly.
 

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