Glossary
TDS 620A, 640A, & 644A User Manual
Cycle RMS
The true Root Mean Square voltage over one cycle.
DC coupling
A mode that passes both AC and DC signal components to the
circuit. Available for both the trigger system and the vertical system.
Delay measurement
A measurement of the time between the middle reference crossings
of two different waveforms.
Delay time
The time between the trigger event and the acquisition of data.
Digitizing
The process of converting a continuous analog signal such as a
waveform to a set of discrete numbers representing the amplitude of
the signal at specific points in time. Digitizing is composed of two
steps: sampling and quantizing.
Display system
The part of the oscilloscope that shows waveforms, measurements,
menu items, status, and other parameters.
Edge Trigger
Triggering occurs when the oscilloscope detects the source passing
through a specified voltage level in a specified direction (the trigger
slope).
Envelope acquisition mode
A mode in which the oscilloscope acquires and displays a waveform
that shows the variation extremes of several acquisitions.
Equivalent-time sampling (ET)
A sampling mode in which the oscilloscope acquires signals over
many repetitions of the event. The TDS 600A Series Digitizing Oscil-
loscopes use a type of equivalent time sampling called
randomequivalent time sampling. It utilizes an internal clock that runs
asynchronously with respect to the input signal and the signal trigger.
The oscilloscope takes samples continuously, independent of the
trigger position, and displays them based on the time difference
between the sample and the trigger. Although the samples are taken
sequentially in time, they are random with respect to the trigger.
Fall time
A measurement of the time it takes for trailing edge of a pulse to fall
from a HighRef value (typically 90%) to a LowRef value (typically
10%) of its amplitude.
Frequency
A timing measurement that is the reciprocal of the period. Measured
in Hertz (Hz) where 1 Hz = 1 cycle per second.