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When observing mains hum on an oscilloscope, it may appear as a stepping voltage rather than a smooth sine wave due to several factors:

  1. Sampling Rate: The stepping voltage appearance can occur if the oscilloscope's sampling rate is not sufficient to accurately capture the high-frequency components of the mains hum. Mains hum typically has a frequency of 50 or 60 Hz, which can result in the oscilloscope not capturing the complete waveform within each sampling interval, leading to an incomplete representation and the appearance of steps.

  2. Triggering: The triggering settings on the oscilloscope can also affect the displayed waveform. If the triggering is not properly set to synchronize with the mains frequency, the waveform may appear distorted or exhibit steps. Adjusting the triggering settings to align with the mains frequency can help display a smoother sine wave.

  3. Noise and Interference: Mains hum often coexists with various forms of noise and interference, such as electrical noise, ground loops, or electromagnetic interference. These external factors can introduce additional irregularities or distortions to the waveform, leading to the stepping voltage appearance on the oscilloscope.

  4. Coupling and Grounding: The choice of coupling and grounding settings on the oscilloscope can impact the observed waveform. Improper coupling or grounding can introduce impedance mismatches or introduce additional noise, resulting in distorted or stepped waveforms.

To obtain a smoother sine wave representation of mains hum on an oscilloscope, you can try the following steps:

  1. Increase the oscilloscope's sampling rate to ensure it captures the high-frequency components of the waveform adequately.

  2. Adjust the triggering settings to synchronize with the mains frequency, ensuring the oscilloscope triggers consistently and displays the waveform accurately.

  3. Minimize noise and interference by using proper shielding techniques, ensuring proper grounding, and reducing nearby sources of electromagnetic interference.

  4. Pay attention to coupling and grounding settings, ensuring they are appropriately configured for the measurement scenario.

By optimizing these settings and minimizing external sources of noise, you can improve the visual representation of mains hum on the oscilloscope, resulting in a smoother sine wave.

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