Introduction to Lab Equipment

Version 1.1Page 1 of 4

ECE 201 – Lab 2

Lab Equipment Introduction

Prelab

Using Ohm's Law, determine the value of the resistor used in the plot in Figure 2.
The current in every household in The United States has a frequency of 60 Hz. What is the period of this current?
If the common wall sockets in the United States supply 120 V (rms), what is the voltage amplitude? What is the peak-to-peak voltage?

Use MATLAB to plot a sinusoidal voltage source with amplitude of 2 V and frequency of 3 Hz from 0 to 2 seconds. On the same graph plot the rms value. Also, on the same graph, plot the sinusoidal with an offset of 1.5 V. Add text to each plot, labeling what it is. For assistance, use the MATLAB help command. Your plot should look like the plot in Figure 3.

When taking DC voltage and current measurements, how would switching the positive and negative leads at the multimeter's input connectors effect the readings?
Would switching the leads effect the resistance reading of an element. Explain.
Select 10 resistors that came with the ECE toolkit and use the multimeter to measure their resistance. Write the nominal resistance as specified by the color bands on the resistor and the measured resistance using the multimeter in Table 1 of the Lab Worksheet. Calculate the tolerance (as a percent error relative to the nominal value) of each resistor and record it in Table 1. Are the tolerances within the nominal specified range?

(k) / Measured Resistance
(k) / Tolerance
(% error)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.

Table 1: Measured Vs Specified Resistance.

When taking AC voltage measurements, how would switching the positive and negative leads at the multimeter's input connectors effect the readings? When taking AC current measurements, how would switching the positive and negative leads at the multimeter's input connectors effect the readings? Hint: think about what a sinusoid looks like and whether the RMS value would be affected by a change in polarity. You do not need to take any measurements to answer this question.
Does switching the leads effect the capacitance read by the multimeter?

Suppose the power supply is configured to have a voltage limit of 9.5 V and a current limit of 0.05 A. If the supply is connected to a 220  load, does it act as a voltage source or a current source? What if it is connected to a 22  load?
With the output enabled, according to the power supply, what are the voltage and current values of the circuit under test? Explain any differences between the settings and the actual values.
Record the voltage and current values displayed on the power supply with the output enabled in Table 2 of the Lab Worksheet. Use the multimeter to measure the total voltage drop and the current through the resistors and record the value in Table 2 of the Lab Worksheet. Do the values measured by the multimeter match the values displayed by the power supply? If there is a difference, is it significant?

Voltage (V) / Current (A)
Power Supply
Multimeter

Table 2: Measured vs. Specified Voltage and Current.

Recall from the prelab exercise that the VRMS value of a sine wave is . Calculate the VRMS value of the default sine wave supplied by the function generator.
What voltage reading is measured with the multimeter? Do not be surprised if it does not match the value from Question 13.
Change the frequency on Channel 1 of the function generator to 10 kHz. Measure the voltage output and record it in your lab worksheet. Does the value match what you expected?
Using the formulas from the prelab exercise, calculate the period waveform with a frequency of 10 kHz.
If you needed a signal with a period of 250 s, at what frequency would you set the function generator?
What is the minimum period that a signal can have and still be read with the multimeter?
Calculate the VRMS for a 1 V, 2 V and 5 V amplitude and record them in Table 3 of the lab worksheet.
Change the amplitude on channel 1 to 2 VP-P. Measure the voltage from this signal with the multimeter and record it in Table 3 in the lab worksheet. Change the amplitude to 5 VP-P and record the measured value in Table 3.

Amplitude (V) / Calculated VRMS (V) / Measure VRMS (V)
1
2
5

Table 3. Calculated Vs Measured VRMS.

Channel 1 of the function generator should have a sine waveform with a frequency of 10 kHz and amplitude of 5 V. Add a 1V DC offset and measure the AC voltage using the multimeter. How does adding a DC offset effect the VRMS value of the waveform?