Table of Contents
Advertisement
Oscilloscope terminology
Clipping: When the 'top' or 'bottom' or both extremes of a signal are cut-of ('clipped'), e.g. because the signal cannot swing
any further due to power supply limitations. An undesired property of amplifiers that are driven beyond their specs. Also
happens when a too small Volt/div setting is selected or the signal the input of the scope is beyond the specs.
DC coupling: The oscilloscope displays both the AC and the DC component of a signal.
DC reference: DC measurement is always performed with respect to a ground level, so we need to define this ground level. If you do not set the DC reference, the
readout might not be correct. In most cases, this ground level will be the center of the screen, however this is not mandatory.
DC voltage: (DC:Direct Current) With DC, the current flows in a single direction, it does not reverse. A DC source has a polarity, (+) and (-).
Digital: Digital scopes perform an analog to digital conversion on the incoming signal and handle all the calculations and displaying in the digital domain. Digital
signals feature only two fixed levels, usually 0V and +5V. See also 'Analog'.
Distortion: Undesired alteration of a signal due to external causes such as overloaded circuits, badly designed circuits, etc...
Free running: When triggering is not enabled, then the unit is in free running mode. A trace is continuously drawn, but the signal will not be stable.
HOLD or HOLD mode: When HOLD mode is active, the screen is not longer updated. It allows you to have a closer look at the signal.
Input coupling: The drawing shows typical oscilloscope input circuit. There are 3 possible settings: AC-coupling, DC coupling and GND.
With AC-coupling, a capacitor is put in series with the input signal. This capacitor blocks any DC component of the signal and passes only AC. With DC
coupling, the capacitor is bypassed and both the AC and DC component of the signal are passed. Low frequency signals (<20Hz) should always be displayed
using DC coupling. Should AC coupling be used, the internal coupling capacitor will interfere with the signal and the displayed signal will not be correct.
AC coupling
DC coupling
GND coupling
- 25 -
Advertisement
Table of Contents
