Display calibration

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 WFDB calibration file (named by the WFDBCAL 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 WFDB calibration file, reset WFDBCAL, 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 wfdbcal(5), in the WFDB 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?''.