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7.3 Sample Rate
Sampling is the process of converting an analog signal into digital data at a specified
time interval and then storing them sequentially in acquisition memory. The sample
rate is the reciprocal of the time interval.
In
Horizontal menu, the "SaRate" item shows the current sample rate. The current
sample rate is also indicated in the acquisition label ("A" icon) at the top of the
screen, as shown in the figure below.
Sample Rate
Sample Interval
The sample rate of the analog channel is related to the instrument model and current
channel mode. For two-channel models (DHO802 and DHO812), the oscilloscope
provides up to 1.25 GSa/s real-time sample rate in single channel mode and 625
MSa/s real-time sample rate in all channels mode. For four-channel models (DHO814
and DHO804), the oscilloscope provides up to 1.25 GSa/s real-time sample rate in
single channel mode, 625 MSa/s real-time sample rate in half channels mode, and
312.5 MSa/s real-time sample rate in all channels mode.
• Single channel mode: If any one of the channels is enabled, it is called single
channel mode.
• Half channels mode: For four-channel models, if two of the channels are
enabled, it is called half channels mode.
• All channels mode: For two-channels models, if all two channels are enabled, it
is called all channels mode; for four-channel models, if any three channels or all
four channels are enabled, it is called all channels mode.
A sample rate that is too low might have the following effects on the waveform:
• Waveform Distortion: When the sample rate is too low, some waveform details
are lost, and the sample waveform displayed is rather different from the actual
waveform of the signal.
• Waveform Aliasing: Aliasing occurs when the sample rate is twice lower than
the actual signal frequency (Nyquist Frequency). The frequency of the waveform
reconstructed from the sample data is smaller than the actual signal frequency.
Acquisition System
DHO800 User Guide
54
Copyright ©RIGOL TECHNOLOGIES CO., LTD. All rights reserved.
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