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Display calibration is performed by WAVE in several steps:
-
First, WAVE determines the display resolution (either
from the -dpi command-line option if possible, otherwise from the
Wave.Dpi resource if possible, or by querying the X server if
neither the command-line option nor the resource was specified).
-
Next, WAVE determines what scales to use for time and amplitude. You
can set these using the Time scale: and Amplitude
scale: menu buttons in the View window. The amplitude scale refers to
standard ECG signals; the default scales (10 mm/mV and 25 mm/sec) are those
used for standard ECG chart recordings. If you choose a non-standard amplitude
scale, WAVE sets its magnification factor to the ratio between that
scale and 10 mm/mV.
-
Finally, if any of the signals to be displayed are not ECGs, WAVE checks
the DB calibration file (named by the DBCAL environment variable) for
entries that specify the standard display scales for those signals. WAVE
multiplies these scales by its magnification factor (see above) in order to
determine the final display scales.
In general, it is not necessary to do anything to make WAVE display
common signals at reasonable scales. If you have a previously undefined signal
type, or you need to change the size of a particular type of signal relative to
that of an ECG, however, simply edit a copy of the DB calibration file, reset
DBCAL, and restart WAVE. (If you wish, you need not exit and
restart WAVE;
instead, give the copy a different name, then change the
Calibration file item in the Load window to match. Any changes are
effective only when the signal window is redrawn.) See
dbcal(5),
in the
ECG Database Applications Guide,
for details.
If the display calibration appears incorrect for all signals, the X
server may be supplying incorrect information about the display size
to WAVE. This problem can be diagnosed by setting the time and amplitude
scales to their default values (nominally 25 mm/sec and 10 mm/mV),
and displaying the default grid (0.5 mV x 0.2 s). If the grid
intervals are not 5 mm in each direction, follow the procedure in
``How can I get correct display scales?''.
Next: Customizing WAVE
Up: Calibration
Previous: Signal calibration
George B. Moody (george@hstbme.mit.edu)
Wed May 7 20:21:25 EDT 1997