TDS 620A, 640A, & 644A User Manual
Glossary
AC coupling
A type of signal transmission that blocks the DC component of a
signal but uses the dynamic (AC) component. Useful for observing an
AC signal that is normally riding on a DC signal.
Accuracy
The closeness of the indicated value to the true value.
Acquisition
The process of sampling signals from input channels, digitizing the
samples into data points, and assembling the data points into a
waveform record. The waveform record is stored in memory. The
trigger marks time zero in that process.
Acquisition interval
The time duration of the waveform record divided by the record
length. The digitizing oscilloscope displays one data point for every
acquisition interval.
Active cursor
The cursor that moves when you turn the general purpose knob. It is
represented in the display by a solid line. The @ readout on the
display shows the absolute value of the active cursor.
Aliasing
A false representation of a signal due to insufficient sampling of high
frequencies or fast transitions. A condition that occurs when a digitiz-
ing oscilloscope digitizes at an effective sampling rate that is too slow
to reproduce the input signal. The waveform displayed on the oscillo-
scope may have a lower frequency than the actual input signal.
Amplitude
The High waveform value less the Low waveform value.
AND
A logic (Boolean) function in which the output is true when and only
when all the inputs are true. On the digitizing oscilloscope, that is a
trigger logic pattern and state function.
Area
Measurement of the waveform area taken over the entire waveform
or the gated region. Expressed in volt-seconds. Area above ground is
positive; area below ground is negative.
Attenuation
The degree the amplitude of a signal is reduced when it passes
through an attenuating device such as a probe or attenuator. That is,
the ratio of the input measure to the output measure. For example, a
10X probe will attenuate, or reduce, the input voltage of a signal by a
factor of 10.