Question

Oscilloscope channel addition problem. Read the following oscilloscope settings carefully. Suppose you display a 1 kHz, 2 V sine wave in channel A and a DC, 1V signal in channel B with sensitivities set on 1V/div. You select 'Add' so that the two signals are combined and you readjust the position so the trace is in the middle of the screen. If you switch the signal in channel B from DC to AC, what will happen? (Draw a picture if it helps.)

Answer 1

Answer:

The signal will move down by 1 division

Explanation:

We have two signals here:

- An AC signal (sine wave), centered at 0 V, with amplitude 2 V (it means that it goes from a maximum of +2 V to a minimum of -2 V)

- A DC signal, which appears in the oscilloscope as a flat line, of 1 V

If we add these two signals together, we are adding a constant offset of +1 V to the sine wave, so the sine wave will move up by one division

Now, if we readjust the position so the trace is centered again at 0 V, we are moving the signal down by 1 division

Then, if we switch the signal in channel B from DC to AC, we are removing the constant offset of 1 V - so the signal will be now centered at -1 V. Therefore, the signal will move down by 1 division.