Chart and Scope Views

The normal view contains one sample per pixel on the x-axis.  However, you can select compression ratios of 2, 2.5, 4, 5, and 10 (these options are available only if the number of chart samples is greater than the number of samples per screen).  Thus with a 640-pixel-wide screen, up to 6400 samples can be shown on a single screen.  The range is 832 - 8320 when using an 832 pixel-wide screen, and so forth with larger screen sizes.

Using the more compressed views increases the amount of recording time that fits on the screen, but at the same time the screen resolution is decreased (for viewing only; not recording) because several samples are plotted within the same x-axis pixel position.

Some combinations of view compression and maximum sample number may generate fractional time units on the X-axis of the chart display.  However, you can manually adjust the scaling of the 'time tics' on the x-axis (if they are used) with the 'use custom tic unit' button (this is automatically selected if you click in the adjacent edit field).

If the number of samples is greater than can be shown on a single DAQ window, the chart display must be scrolled when the data plot reaches the window's right edge.  The default scrolling value is 100% -- that is, the entire window is redrawn, showing none of the previously-acquired data.  Alternately you may select fractional scrolling (50%, 67%, 75%, or 90%), which leaves some of the previously-acquired data in view.
        Another option, which works only at low sample rates, is 'Continuous' scrolling.   In this mode, once data lines reach the right edge of the DAQ window, the window is scrolled one pixel at a time as additional data are obtained.   If you sample too fast, data will be acquired -- and can be saved --successfully, but the display updating will 'get behind' and seem to pile up at the right edge:   display updating will lag behind data acquisition.  The program will let you do this but it may be cosmetically ugly and confusing as well.   The sampling rates that cause this problem depend on the number of channels, the speed of the computer's graphics engine, and other factors, but very roughly, you can expect normal function with 6-10 channels if sampling rates are slower than 2-4 samples/sec.

  •   SCOPE VIEWS AND TICS...      opens a window that allows selection of the 'density' of data plotted in chart mode.  It is similar to Chart view, except that it offers options to display only a fraction of the gathered data (all the data will be saved if a file is stored).  Reducing the number of points displayed can greatly increase the display rate (and hence the fraction of total time spent in sampling data) -- although this is rarely a limitation with fast, modern Macs and relatively slow A-D converters.  For all practical purposes, you should use the "show every point" option.

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