X-Y Plotting Operations > Area

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Calculating Areas Bound By Curves

Using the cross hair to target specific bound areas of the X-Y plot, it is possible to determine the area bound by the curve. When the desired X-Y plot is displayed on the screen and the plot area to be determined is completely enclosed, adjust the cross hair such that its origin lies within the area to be determined. To fill the enclosed area and calculate the area it occupies:


  In the XY menu click on Area.


   Choose X-Y Area (ALT, X, A).


When the area function is activated, the desired plot area is filled and the analysis reporting area will display:


Where the value to the left of NEWAREA is the area of the bound curve just filled, and the value to the left of TOTAREA is the accumulated result of all bound and filled areas. The latter quantity (TOTAREA) is possible since multiple area fills are possible for any given plot by repositioning the cross hair to a new area and filling again as described above (ALT+F3 is the quickest). As consecutive areas of an X-Y plot are filled, TOTAREA accumulates a total while NEWAREA displays the area of the last fill. Any given area may be unfilled by positioning the cursor within the filled area and pressing ALT+F3 a second time. When this feature is activated, NEWAREA will display a negative number equal to the area eliminated and TOTAREA will decrease by an equal amount.


The value displayed for NEWAREA and TOTAREA is in units of channel X's units times Channel Y's units. For example, if channel X's Y-T waveform is calibrated in units of PSI and channel Y's in units of Liters, area is expressed in units of Liters ยท PSI.


When using ALT+F3 to fill areas, it is possible for the screen to fill completely if the selected area was not completely bound. If this happens, pressing ALT+F3 a second time without moving the cross hair will unfill the screen. X-Y plots appearing on your screen that are not bound (i.e., areas that are not completely surrounded by an X-Y trace) may be forced closed by:


  In the XY menu click on Clear Areas.


   Choosing X-Y Clear Areas (ALT, X, C).


When this feature is activated, the two end points of the X-Y plot are connected with a straight line allowing the now closed area to be calculated using the procedure described above. If Clear Areas is chosen while there are active area fills on the screen, they will be cleared and NEWAREA and TOTAREA are reset to zero.