Trace Update Interval

Macro: TraceUpdate

The Trace Update control sets the interval between display updates. Note that this only affects the rate at which data is displayed; it has nothing to do with acquisition of data.

The Trace Update interval works together with the Trigger process. At each Trace Update interval, Daqarta tests to see if the specified trigger event has occurred since the last display update and shows the new trace if so. If not, it waits for the next Trace Update.

If Trigger is toggled off (free-run) then traces will be shown at the Trace Update interval unless Trigger Holdoff is set to a higher value.

The Trace Update value defaults to the system timer resolution. For Windows NT/2000/XP single-processor systems this is 10 msec, which will give a free-run update rate of 100 frames per second if the system can process and display data fast enough. For multi-processor systems the default is 15 msec (66.7 frames per second). Windows 95/98/Me systems default to 55 msec, which is just under 20 frames per second.

You can set longer intervals in steps of 1 msec, but only multiples of the timer resolution msec will have a visible effect. You may want to keep Trace Update at its default value and use Trigger Holdoff for longer intervals intervals.

You might think that faster is always better, but that's not always the case. Update rates faster than the eye can follow may be simply wasting processing time, possibly causing poor control response on overburdened systems. In fact, you may wish to sometimes deliberately slow the updates, such as to produce a Spectrogram ( Sgram) that shows a long time span on a single screen. (That assumes, of course, that the signal is not changing too rapidly.)

On the other hand, for maximum speed of live spectrograms (best time resolution), you should set the update interval as low as your system allows. (Spectrograms of file data aren't affected by this control; use Read Step Size instead.)

Macro Notes:

TraceUpdate=10 sets Trace Update directly to 10 msec. TraceUpdate=>1 increments the current value by 1 msec, and TraceUpdate=>-1 decrements by 1 msec.

See also X-Axis Control Dialog