Selecting Ac-Coupling - Extech Instruments MS400 User Manual

Term Glossary
Collecting mode: The oscilloscope transforms the collected analog data into a digital
form after it is gathered in the following three modes: sampling, peak value detection
and averaging values.
Sampling: The oscilloscope takes samples from the signal at equal time intervals to
reconstruct the waveform. In this mode, the analog signal can be expressed correctly
in most cases. However, rapid changes cannot be detected between two sampling
time intervals.
Peak value detection: The oscilloscope takes samples from the maximum and
minimum of signals in each sampling interval and shows the Waveform with the
sampled data. Thus, the oscilloscope may capture narrow pulses that could not be
detected in sampling mode.
Averaging values: The oscilloscope collects several Waveforms, averages them,
and displays the averaged Waveform. In this mode random noise can be reduced.
Duration time: When a new Waveform is displayed, the previous Waveform shown
on the screen does not disappear immediately but will continue to be displayed for a
period of time. This period of time is referred to as the duration time. Thus, a display
similar to that shown by an analog oscilloscope can be achieved.
Roll scan mode: The oscilloscope updates the Waveform sampling points by
scrolling through the screen from left to right (only applicable to the primary time base
setting above 50ms).

Selecting AC-Coupling

After a reset, the Oscilloscope is dc-coupled so that ac and dc voltages appear on the
screen. Use ac-coupling to observe small ac signals that ride on a dc signal. To select
ac-coupling:
1. Press the MENU key and the function menu will appear at the right side of the
screen.
2. Press the MENU UP or the MENU DOWN key to select the CH1 SETUP. Four
selectable items are visible at the bottom of the screen.
3. Press the F1 key and jump to AC. The bottom left side of the screen displays the ac-
coupling icon.
The user can view a screen that looks similar to the following Figure 17.
Figure 17: AC-Coupling
21 MS400 Version 2.0 – December 2007