Sampling oscilloscope concepts
Sampling oscilloscope concepts
Read this section if you are a new oscilloscope user, or are new to using a digital oscilloscope.
Sampling and acquisition concepts
Before the oscilloscope can display or measure a signal, it must be sampled.
Sampling
is the process of measuring the
input signal amplitude value at regular intervals (called the sampling rate, in samples per second), converting the sampled
levels into digital data, and storing the sampled values in memory to create a
waveform record
. The oscilloscope uses
the digitized values in the waveform record to create, display, and measure waveforms. Each oscilloscope channel has
its own waveform record memory storage.
TBS2000 Series oscilloscopes use real-time sampling. In real-time sampling, the oscilloscope samples and digitizes all
of the sampled points at one time, in sequence, stores the sampled data in memory, and then repeats the sampling and
storage process.
You use the
Horizontal Scale
knob to change the sample rate (samples per second). The oscilloscope automatically sets
the sample rate so that there are more than enough samples to accurately capture the signal information. The sample rate is
shown on the screen at all times in the horizontal position/scale readout. See item 11 in
The graphical user elements
section.
NOTE.
The maximum sample rate of 1 GS/s is only available when one channel per channel pair is active (channel 1, 2
pair or channel 3, 4 pair).
For two-channel models, only one channel (either channel 1 or 2) can sample at 1 Gs/s. If channel 1 and 2 are both
active, then the maximum sample rate changes to 500 MS/s.
On four-channel models, only two channels can sample at 1 GS/s (one channel from each pair). So if channel 1 or 2, and
channel 3 or 4, are active, the maximum sample rate is available. Turning on a 3rd channel (in either pair) changes the
maximum sampling rate to 500 MS/s.
You can set the waveform
record length
(number of sample points in the waveform record) from 2000 points to 20 million
points (20M). A longer (larger) waveform record is useful to capture several waveform cycles to search for a waveform of
interest, or to capture a great deal of detail for just a few waveform cycles and then use the
Zoom
function to search
the waveform for areas of interest.
Each time the oscilloscope
fi
lls the waveform record is called a
waveform acquisition
, or
acquisition
for short. Acquisitions
happen up to 10,000 times a second, for all channels. Each acquisition stores new sample data into the same waveform
record for that channel.
A waveform record is further divided into
acquisition intervals
, which are equally sized groups of samples. Acquisition
intervals let the oscilloscope perform calculations to analyze and display data such as the minimum and maximum data
values per interval, or the average signal value per interval. How the values in the acquisition interval are used is set
by the acquisition mode.
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TBS2000 Series User Manual
