Lab 2: Practical Voltage and Current Measurement

Objective: 

Observe the changes in the voltage v(out) based on the differences in internal resistances for ideal and non-ideal voltmeters.

Pre-lab:

Analyze the circuit of Figure 1 to determine an expected value for the measured voltage v(out) for the cases in which the measurement of v(out) is determined using an ideal voltmeter (a voltmeter with infinite internal resistance)

Ideal Voltage = 2.50 Volts

Procedure:

Set up the circuit as shown in figure 2.1. (See Figure 2.2 for how it should look)

Measure the internal resistance with a voltmeter.

Measure the internal resistance with analog discovery.

Lab Results:

1.       Provide the expected output voltage for an ideal voltmeter based on your pre-lab analysis.

Ideal Voltage: 2.50 Volts

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

Figure 2.1 – Diagram of the Circuit as provided from the handout.

Figure 2.2 – Actual setup of the Circuit in class. We used the 10 M(Ohm) resistors in class.

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.

Figure 2.3 – Setup of the circuit and the measured volt using the DMM. The DMM recorded a value of 2.41 Volts. This is relatively close to an ideal voltmeter, which would have read 2.50 Volts. This is due to the relatively small internal resistance of the DMM. The effect of internal resistance tends to vary depending on the value of the resistors.

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.

We were not able to figure out how to use the Analog Discovery. When using it, we would get very bizarre values for voltage. (~0.684 V) This is nowhere near the expected value. Even when brainstorming with classmates, no one in the class was able to figure it out. (Not even Kyle)