Data AcQuisition And Real-Time Analysis
Scope - Spectrum - Spectrogram - Signal Generator
Software for Windows
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The following is from the Daqarta Help system:



Spectrum Analyzer

Signal Generator

(Absolutely FREE!)


Pitch Tracker


DaqMusiq Generator
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Engine Simulator

LCR Meter

Remote Operation

DC Measurements

True RMS Voltmeter

Sound Level Meter

Frequency Counter
    Spectral Event

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Data Logger

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Post-Stimulus Time
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THD Meter

IMD Meter

Precision Phase Meter

Pulse Meter

Macro System

Multi-Trace Arrays

Trigger Controls


Spectral Peak Track

Spectrum Limit Testing

Direct-to-Disk Recording



Frequency response

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X-Axis eXpand

Controls: X-Axis Dialog >> eXpand
Macro: Xpand

This button duplicates the X-Axis button on the Daqarta toolbar. You can also toggle with ALT+X. When active, the X axis expands to the limits set by the Max and Min controls below it.

The expansion simply changes the spacing between data points for easier viewing; it does not increase actual resolution.

There are separate eXpand states and Max and Min limits for waveform, Histogram, and Spectrum modes, as well as for X-log Spectrum, Spectrogram, and Spectrogram Pitch Track. In the Spectrogram modes, eXpand actually operates on the Y (frequency) axis. (Note that the eXpand controls are duplicated in the Spectrogram / Pitch Track Control dialog for convenience.)

Besides setting the Max and Min limits manually and hitting this eXpand button, you can also expand the region between the cursors at any time by hitting CTRL+ALT+X. If eXpand is not active, that will activate it, and Max and Min will be forced to the values under the solid and dotted cursors. Whichever cursor is at the lowest X-value will set Min, and the highest will set Max.

Additionally, you can scroll Min with the horizontal arrow buttons at the left end of the X axis, and scroll Max with those at the right end. Alternatively, you can drag the X axis left or right with the mouse. Dragging to the left moves Min down, while dragging to the right moves Max up. To move Min up, start dragging to the left and then without lifting the button drag to the right. To drag Max down, start dragging to the right and then to the left.

eXpand is toggled on automatically by these scrolling or dragging operations. Use the X-Axis button (ALT+X) or the eXpand button to toggle it back off.

In waveform mode, the eXpand state is active by default to show only the first 512 points of the waveform, even though 1024 data points are collected. That's because all screens can resolve 512 horizontal pixels, even at 640x480 resolution.

If eXpand is set to show more points than the screen supports, it simply means that some of the points will overlap. The cursors will still move one point at a time using the arrow keys, which will be seen on the readouts, even if the cursor doesn't appear to move because both points share the same horizontal pixel position. Positioning the cursors with the mouse will still work, but you won't be able to get the finest resolution.

In Spectrum modes, the same 1024 points yield 512 spectral lines, so there is normally no issue regarding screen resolution. However, regardless of the screen, in X-log mode the high frequencies will typically be compressed as a result of the logarithmic axis. Points will then overlap and the same issues with cursor position will arise. Just use the cursor keys for finest control.

For Spectrogram and Pitch Track modes, note that changes to the eXpand state or Max/Min limits only apply from the current time point onward. Any prior time points that may be visible on the screen are unchanged until they are eventually overwritten.

Also note that in Spectrogram or Pitch Track modes you can change Max and Min by dragging the vertical (Y) axis instead of the X axis. However, the horizontal scroll buttons at either end of the X axis still control Max and Min as described above. (The vertical scroll buttons control Spectrogram color range.)

Macro Notes:

Xpand=1 sets eXpand mode, Xpand=0 turns it off, and Xpand=x toggles between on and off.

See also X-Axis Control Dialog


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