*Question E4A06:
What is the effect of aliasing on a digital oscilloscope when displaying a waveform?*  

*Correct Answer is  A: A false, jittery low-frequency version of the waveform is displayed*  

### AI Response: (may contain errors)  

Aliasing is a phenomenon that occurs when a digital oscilloscope samples a waveform at a rate that is too low to accurately capture its high-frequency components. This can lead to a misrepresentation of the waveform, often displaying a false, lower-frequency version of the original signal. Here's why the correct answer is A:

1. **Correct Answer: A false, jittery low-frequency version of the waveform is displayed**  
   - When the sampling rate is less than twice the highest frequency component of the waveform (violating the Nyquist-Shannon sampling theorem), aliasing occurs. This results in the oscilloscope displaying a waveform that appears to have a lower frequency than the actual signal. This false representation can also appear jittery due to the insufficient sampling rate.

2. **Why the other choices are incorrect:**
   - **B: The waveform DC offset will be inaccurate**  
     - Aliasing primarily affects the frequency representation of the waveform, not the DC offset. The DC offset is a constant value and is not influenced by the sampling rate.
   - **C: Calibration of the vertical scale is no longer valid**  
     - Aliasing does not affect the vertical scale calibration. The vertical scale is related to amplitude measurement, which is independent of the sampling rate.
   - **D: Excessive blanking occurs, which prevents display of the waveform**  
     - Blanking refers to the oscilloscope's ability to hide parts of the waveform during retrace. Aliasing does not cause excessive blanking; it causes a misrepresentation of the waveform's frequency.

3. **Useful Rule of Thumb:**
   - To avoid aliasing, ensure the oscilloscope's sampling rate is at least twice the highest frequency component of the signal, as per the Nyquist-Shannon sampling theorem:  
     $$ f_s \geq 2f_{\text{max}} $$  
     where $f_s$ is the sampling rate and $f_{\text{max}}$ is the maximum frequency of the signal.