Pico Macom Pico Technology PicoScope 4000 Automotive PC Oscilloscopes - Manual (Page 13)

Glossary 9
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4 Glossary
AC/DC control. Each channel can be set to either AC coupling or DC coupling. With
DC coupling, the voltage displayed on the screen is equal to the true voltage of the
signal with respect to ground. With AC coupling, any DC component of the signal is
filtered out, leaving only the variations in the signal (the AC component).
Aliasing. Like all digital scopes, the PicoScope 4000 Series cannot reliably capture
signals with a frequency higher than half the scope's maximum sampling rate. For
example, with a 80 MS/s sampling rate, the frequency limit is 40 MHz. If the signal
frequency exceeds this limit then a distorted waveform appears. This distortion is
called aliasing.
Analog bandwidth. All oscilloscopes have an upper limit to the range of frequencies
at which they can measure accurately. The analog bandwidth of an oscilloscope is
defined as the frequency at which a displayed sine wave has half the power of the
input sine wave (about 71% of the amplitude).
Block mode. A sampling mode in which the computer prompts the oscilloscope to
collect a block of data into its internal memory before stopping the oscilloscope and
transferring the whole block into computer memory. This mode of operation is
effective when the input signal being sampled is high frequency. Note: To avoid
aliasing effects, the maximum input frequency must be less than half the sampling
rate.
Buffer size. The size of the oscilloscope buffer memory. The buffer memory is used
by the oscilloscope to temporarily store data. This helps to compensate for the
differences in data transfer rate from one device to another.
Maximum sampling rate. A figure indicating the maximum number of samples the
oscilloscope is capable of acquiring per second. Maximum sample rates are usually
given in MS/s (megasamples per second) or GS/s (gigasamples per second.) The
higher the sampling capability of the oscilloscope, the more accurate the
representation of the fine details in a fast signal.
PC Oscilloscope. A generic term used to describe a PicoScope 4000 Series
Automotive PC Oscilloscope and the PicoScope software application.
PicoScope 4000 Series Automotive. An oscilloscope range comprising the
PicoScope 4223 and PicoScope 4423 Automotive PC Oscilloscopes.
PicoScope software. This is a software product that accompanies all our
oscilloscopes. It turns your PC into an oscilloscope, spectrum analyser, and meter
display.
Spectrum analyser. An instrument that measures the energy content of a signal in
each of a large number of frequency bands. It displays the result as a graph of
energy (on the vertical axis) against frequency (on the horizontal axis). The
PicoScope software includes a spectrum analyser.
Streaming mode. A sampling mode in which the oscilloscope samples data and
returns it to the computer in an unbroken stream. This mode of operation is effective
when the input signal being sampled is low frequency.
Timebase. The timebase controls the time interval across the scope display. If you
select Timebase is time per division in the Preferences dialogue box, this works
like a traditional bench top scope. There are ten divisions across the screen, so the
total time interval is ten times the timebase.
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