Lab 2: Practical Voltage

Lab 2: Practical Voltage and Current Measurement

Introduction

In this lab assignment, we will experimentally explore the behavior of non-ideal meters. The experiments in this assignment illustrate the effects of non-ideal voltage measurements.

Procedure

1) Construct the circuit below. Measure the voltage V-out using the DMM. Estimate the internal resistance of the voltmeter.

2) Take a picture of the circuit and include in blog.
3) Repeat the test of part (1), except use the voltmeter on the Analog Discovery module to measure V-out. Estimate the internal resistance of the scope instrument.

Analysis

1. Provide the expected output voltage for both ideal and non-ideal voltmeters, based on your pre-lab analysis.

2. Provide a circuit schematic below; include measured resistance values on your schematic.

3. Provide your measured output voltage and your estimated value of the internal resistance of the voltmeter of your DMM. Comment on your results, especially relative to the effects of the voltmeter on the quantity being measured.

4. Provide your measured output voltage and your estimated value of the internal resistance of the voltmeter of your Analog Discovery. Comment on your results, especially relative to the effects of the voltmeter on the quantity being measured.

Conclusion

Very large resistors are used in the voltage divider circuit above. Due to these large resistances, measurement of the voltage V out will likely result in measurement errors due to non-ideal voltmeter effects. It can be seen that if R>>Rm, R eq and the measured V out will be essentially the same as the idealized V out. If R>>Rm is not true, the voltmeter’s internal resistance can have a
significant change on the voltage being measured.