Specifications

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phosphor
A chemical used to coat the inside of a CRT. When struck by fast-moving
electrons, the orbital electrons of the phosphor are excited to higher energy
levels using the kinetic energy of the incoming electrons. When the atoms
decay back to their lower energy states (usually, the ground state), they
release a photon. This photon escapes the glass CRT and registers as an
oscilloscope trace on a human's eye.
post-trigger
The time period after the trigger event.
post-trigger data
The digitized waveform data collected after the trigger event.
pre-trigger
The time period before the trigger event.
pre-trigger data
The digitized waveform data collected before the trigger event.
probe
An oscilloscope accessory device used to couple the oscilloscope's input
channel to a circuit to be measured.
pulse
A rapid, transient change in the amplitude of a signal from a baseline value to
a higher or lower value, followed by a rapid return to the baseline value.
pulse period
The time that a periodic pulse train repeats itself.
pulse train
A sequence of one or more pulses.
pulse width
The width of a pulse, measured while the pulse's value is at the non-baseline
value.
ramp
A voltage that linearly increases or decreases from a starting value, then
quickly returns to the starting value. The horizontal (time axis) deflection
voltage in an analog oscilloscope's CRT is a ramp voltage.
raster
The representation of a two-dimensional image by turning small sections of
the display screen (pixels or picture elements) on and off. In the analog world,
it refers to the rapid scanning back and forth of an electron beam, each line
displaced vertically a small amount from the last line, and resulting in a
displayed image. This is the way analog televisions and older computer
displays worked.
real time sampling
A sampling method of digital scopes where the signal is directly sampled. It is
used to measure and display transient, non-repeating signals. Contrast to
equivalent-time sampling.
record length
The number of data points representing a trace on a digital oscilloscope.
rise time
The time required for a signal to rise from 10% to 90% of its maximum
amplitude (other percentages can be specified, such as 20% to 80%). With a
fast rise time pulse, the rise time specification of the oscilloscope can be
measured. An oscilloscope's rise time specification is directly related to its
bandwidth:
risetime in a scope in ns
=
350
bandwidth in MHz
RMS
Root mean square. It is a positive measure of the amplitude of a periodic
waveform and used to predict the power dissipation in a resistive element.
The
analog definition involves an integral. For a sampled waveform, the RMS val
ue
is the square root of the mean of the squares of the data values (i.e., square
each value, take their sum, divide by the number of values, and then take the
square root).
sampling
The process of taking samples of a waveform at regular intervals. This
converts a continuous analog signal into a sequence of numbers. The term
can also refer to equivalent time sampling methods.
sampling rate
A fundamental measure of the digitizing abilities of a digital scope, as in the
context of the sampling theorem. It is the frequency in Hz (or it can be
expressed in samples per second Sa/s) of the samples being taken.
sampling scope
An oscilloscope that uses equivalent time sampling methods to display high
frequency signals that lie beyond the sampling rate of the oscilloscope.
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