*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 occurs when a signal is sampled at a rate that is insufficient to capture its changes accurately. This can lead to misleading representations of the waveform on a digital oscilloscope.

### Explanation of the Correct Answer:
- **Correct Answer: A**  
  When aliasing occurs, the digital oscilloscope samples the waveform at a rate lower than the Nyquist rate, which is twice the highest frequency present in the signal. As a result, the displayed waveform appears as a false, jittery low-frequency version of the actual signal. This happens because the oscilloscope cannot accurately reconstruct the original waveform from the insufficient samples.

### Explanation of the Incorrect Answers:
- **B: The waveform DC offset will be inaccurate**  
  While aliasing can affect the representation of the waveform, it does not specifically cause inaccuracies in the DC offset. The DC offset is determined by the average value of the signal, which is not directly impacted by aliasing.

- **C: Calibration of the vertical scale is no longer valid**  
  Aliasing does not invalidate the calibration of the vertical scale. The vertical scale calibration is related to the oscilloscope's ability to measure voltage levels accurately, which remains valid regardless of aliasing.

- **D: Excessive blanking occurs, which prevents display of the waveform**  
  Blanking refers to the oscilloscope's ability to suppress the display of certain signals, typically during retrace periods. Aliasing does not cause excessive blanking; instead, it results in a misrepresentation of the waveform.

### Useful Rules of Thumb:
- **Nyquist Rate**: To avoid aliasing, ensure that the sampling rate is at least twice the highest frequency of the signal being measured. This is known as the Nyquist criterion.
  
- **Sampling Rate**: A common rule of thumb is to sample at 5 to 10 times the highest frequency of interest to ensure accurate representation and minimize aliasing effects.

By understanding these concepts, you can better interpret the effects of aliasing on digital oscilloscopes and ensure accurate waveform analysis.