User manual

WaveSurfer 3000/3000z Oscilloscopes Operator's Manual
Memory
Maximum Points is the maximum number of samples taken per acquisition. The actual number of
samples acquired can be lower due to the current Sample Rate and Time/Division settings.
The oscilloscope will allot the maximum memory and sample rate possible based on the activity within
each pair of channels. As long as only one channel in each of the C1-C2 and C3-C4 pairs is turned on, the
interleaved rate is used. Turning on both channels in either pair reduces memory and sample rate to the
standard, 4-channel specification.
To avoid aliasing and other waveform distortions, it is advisable (per Nyquist) to acquire at a sample rate at
least twice the bandwidth of the input signal. Use Maximum Points in relation to Time/Division to adjust
the overall Sample Rate (shown on the Timebase descriptor). The formula for sample rate is: Sample Rate
= Memory Samples/Acquisition Time, with the maximum sample rate being limited by the instrument's
analog-to-digital converter (ADC).
Sampling Modes
The Sampling Mode determines how the instrument samples the input signal and renders it for display.
Average Sampling Mode
Average sampling mode calculates the average value for each captured point over a specified number of
acquisitions. Each individual acquisition uses Real Time mode and the results are averaged together.
Average mode can be used to reduce random noise in repeating signals.
When selecting Average sampling mode, also select the number of Sweeps to calculate in the Average.
The Max Memory Length you can set for Average sampling mode is 10 kpts. This limit applies only to the
hardware acquisition system. You can apply the Average math function to larger acquisitions.
Real Time Sampling Mode
Real Time sampling mode is a series of digitized voltage values sampled on the input signal at a uniform
rate. These samples are displayed as a series of measured data values associated with a single trigger
event. By default (with no Delay), the waveform is positioned so that the trigger event is time 0 on the grid.
The relationship between sample rate, memory, and time can be expressed as:
Capture Interval = 1/Sample Rate X Memory
Capture Interval/10 = Time Per Division
Usually, on fast timebase settings, the maximum sample rate is used when in Real Time mode. For slower
timebase settings, the sample rate is decreased so that the maximum number of data samples is
maintained over time.
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