Glossary
TDS 684A, TDS 744A, & TDS 784A User Manual Glossary–9
fill a waveform record from a single trigger event. Use real-time sampling to
capture single-shot or transient events.
Record length
The specified number of samples in a waveform.
Reference memory
Memory in a oscilloscope used to store waveforms or settings. You can use
that waveform data later for processing. The oscilloscope saves the data even
when the oscilloscope is turned off or unplugged.
Rise time
The time it takes for a leading edge of a pulse to rise from a LowRef value
(typically 10%) to a HighRef value (typically 90%) of its amplitude.
RMS
Amplitude (voltage) measurement of the true Root Mean Square voltage.
Runt trigger
A mode in which the oscilloscope triggers on a runt. A runt is a pulse that
crosses one threshold but fails to cross a second threshold before recrossing
the first. The crossings detected can be positive, negative, or either.
Sample acquisition mode
The oscilloscope creates a record point by saving the first sample during
each acquisition interval. That is the default mode of the acquisition.
Sample interval
The time interval between successive samples in a time base. For real-time
digitizers, the sample interval is the reciprocal of the sample rate. For
equivalent-time digitizers, the time interval between successive samples
represents equivalent time, not real time.
Sampling
The process of capturing an analog input, such as a voltage, at a discrete
point in time and holding it constant so that it can be quantized. Two general
methods of sampling are: real-time sampling and equivalent-time sampling.
Setup/Hold trigger
A mode in which the oscilloscope triggers when a data source changes state
within the setup or hold time relative to a clock source. Positive setup times
precede the clock edge; positive hold times follow the clock edge. The clock
edge may be the rising or falling edge.
Select button
A button that changes which of the two cursors is active.