Acquisition Modes

Question: What acquisition modes are available on most Tektronix oscilloscopes?

Answer: Here’s an overview of 8 acquisition modes commonly available.

Sample mode: The most basic of all the modes, sample mode delivers the highest accuracy for timing interval measurements. It retains and displays the first point from each sample interval, discarding the others. In many DSOs, sample mode interleaves the digitizers of two or more channels to achieve the instrument’s maximum sample rate.

Peak Detect mode: Determines the highest and lowest values for each sample interval, then displays all the samples between the two values, inclusive. Especially useful at slower sampling rates, Peak Detect allows you to see any extremes that occurred during the sample interval.

High Resolution (Hi-Res) mode: A Tektronix-patented process that calculates and displays the average of all the values in each sample interval. It runs at the highest sampling rate of the digitizer, providing maximum detail in the acquired waveform. It does not interleave channels. Because it works with more data per sample interval, Hi-Res mode increases the effective vertical measurement resolution. Sample, Peak Detect, and Hi-Res modes operate in real time, using the acquired data from one trigger event. Therefore these modes are suitable for the most demanding, single-shot measurements at frequencies up to the oscilloscope’s upper bandwidth limit. The remaining modes require a repetitive signal.

Waveform Database mode: The waveform database is a three-dimensional accumulation of source waveform data over several acquisitions. In addition to amplitude and timing information, the database includes the number of times a specific waveform point (time and amplitude) has been acquired. Using waveform database technology, the real-time oscilloscope processes a much larger sample of data than when using the sample acquisition mode.

DPO FastAcq mode: FastAcq optimizes the oscilloscope for analysis of dynamic signals and capture of infrequent events.

Average mode: Using the data from two or more acquisitions, this mode averages the corresponding data points on a point-by-point basis. Average mode improves the signal-to-noise ratio, removes uncorrelated noise, and makes viewing of repetitive signals easier.

Envelope mode: Builds a waveform “envelope” from the highest maximum values and lowest minimum values among the corresponding samples from two or more trigger events (acquisitions). Envelope mode is similar to Peak Detect mode (and in fact uses some Peak Detect capabilities) but is best used on repetitive waveforms, where it minimizes aliasing effects.

Random Equivalent Time (ET) mode: Accumulates a waveform record from acquisitions over many trigger events. The samples from any one trigger occur randomly with respect to samples from any other trigger, so eventually, samples will fill all parts of the waveform record. ET mode may capture several samples during any one acquisition, but cannot be used on single-shot signals. ET mode requires a repetitive waveform that remains consistent from trigger to trigger. In a DSO, random ET sampling allows sampling at rates higher than the oscilloscope’s nominal Nyquist frequency limits.

Explore posts in the same categories: Ask Scope Guru Q/A, Oscilloscope Fundamentals


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