Simulation Lab (EC-406) - Important Questions

Describe, step-by-step, how to measure the peak-to-peak voltage $V_{pp}$, RMS voltage $V_{rms}$, frequency $f$ and phase difference $\phi$ between two sinusoidal signals using a virtual oscilloscope. Your answer must include probe connection and grounding, probe compensation, setting the timebase and volts/div, selecting appropriate coupling (AC/DC), triggering strategy, use of measurement cursors, and the formulas $f=\frac{1}{T}$ and $\phi=360\times\frac{\Delta t}{T}$ where $T$ is the period and $\Delta t$ is the time difference between corresponding points on the two waveforms.

Explain the procedure to configure a virtual function generator to produce sinusoidal, square and PWM signals. Describe how to set frequency, amplitude, DC offset and duty cycle. Then explain how to capture these signals on a virtual oscilloscope and measure rise time, fall time and duty cycle. Include the configuration steps for dual-trace measurement and suggestions to minimize measurement error.

Describe the process of probe compensation for a 10:x oscilloscope probe using a virtual oscilloscope. Show how an uncompensated probe distorts a 1:kHz square wave and explain how to adjust the probe to obtain the correct square waveform. State typical symptoms of under-compensation and over-compensation.

Using a virtual multimeter, outline the steps to measure (a) the forward voltage drop of a silicon diode in a simple series circuit, and (b) the current through a series resistor. Include how to select ranges, how to connect the multimeter for voltage and current measurements, and typical expected values for a silicon diode forward voltage at small forward currents.

Explain how to use the FFT (spectrum) function of a virtual oscilloscope to analyze a complex periodic signal. Describe the effects of windowing and resolution bandwidth on the spectrum, how to identify fundamental and harmonic components, and how to compute total harmonic distortion (THD) using $$\mathrm{THD}=\frac{\sqrt{\sum_{n=2}^{N}V_n^{2}}}{V_1}$$ where $V_1$ is the RMS amplitude of the fundamental and $V_n$ are the RMS amplitudes of the harmonics.

Describe a procedure to estimate the bandwidth $BW$ of a virtual oscilloscope from a measured rise time $t_r$ of a fast pulse. State and use the relation $$t_r\approx\frac{0.35}{BW}$$ and explain limitations of this method in a simulated environment compared to measurements with physical hardware.

Compare and contrast virtual instruments (virtual oscilloscope, virtual function generator, virtual multimeter) with their physical counterparts in terms of accuracy, bandwidth, noise, user interface, calibration needs, and suitability for different types of laboratory exercises.