Advanced acquisition concepts are demonstrated in the Tektronix MDO3104 Oscilloscope.
We’ll look at the FastAcq capability in the amazing Tektronix MDO 3000 Series oscilloscope, together with some related signal acquisition concepts.
We’re feeding a simple sine wave from the internal arbitrary function generator into one of the analog channel inputs, whereupon it is digitized, placed in memory and displayed on the screen.
First we’ll press Acquire. This is the gateway to copious functionality, as we shall see. Pressing Acquire brings up the Acquisition Menu across the bottom below the display. The first item on the left is Mode. When the corresponding soft key is pressed, the Acquisition Menu appears to the right of the display. The first three choices starting at the top are Sample, Peak Detect and Hi Res. Each of these affects the signal as displayed in a different way.
Sample is the default mode. It retains the first sampled point from each acquisition interval.
Another acquisition mode, this one working only in real time, non-interpreted sampling, is Peak
Detect. It uses the highest and lowest of all samples occurring in two consecutive acquisition intervals. It is a valuable tool for displaying high-frequency glitches, which would otherwise be very difficult for the oscilloscope user to see.
High Res mode is a technique for eliminating noise that may contaminate a signal. Like Peak Detect, this method functions in real-time, non-interpolated sampling. By temporarily limiting the bandwidth, broad-spectrum noise is reduced, allowing the genuine signal to be seen.
Envelope Mode employs Peak Detect on the level of each individual acquisition in order to display the highest and lowest record points in the full range of acquisitions.
Average Mode is another very effective method for dealing with noise that is obscuring a signal. The user specifies the number of acquisitions to be averaged and then the oscilloscope performs the operation. Since noise is a random event, the averaging process cancels it out, while the actual signal, which is repetitive, persists and is displayed in great clarity.
Notice that as the number of waveforms to be averaged is increased, using Multipurpose Knob a, the trace becomes continuously clearer. The minimum number of cycles that can be averaged is of course two and the maximum number in this Tektronix 3000 series oscilloscope is 512.
FastAcq, just as the name suggests, speeds up the oscilloscope, revealing signal anomalies that would otherwise elude the user. Runt pulses and glitches become visible in the display. Another function of FastAcq is that it displays waveforms so that the intensity corresponds to the rate at which they occur.
FastAcq is invoked simply by pressing Acquire. Then, in the Acquisition menu that appears across the bottom, press the soft key that goes with FastAcq. This allows this informative function to be toggled On in the vertical submenu. Once it has been switched On, Waveform Palette Temperature can be set. If noise is added, there is a colorful display that reveals its spectral distribution relative to the original signal.
Now, with the same settings, lets take a look at the Noise waveform, if you want to see a vivid
display of colors corresponding to a very broadband phenomenon.
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