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3.2 Calibration Information Structures

The cal argument for getcal and putcal is a pointer to an object of type WFDB_Calinfo. A WFDB_Calinfo object contains information about signals of a specified type:

char *sigtype

a pointer to a null-terminated string without embedded tabs or newlines. This field describes the type(s) of signals to which the calibration specifications apply. Usually, sigtype is an exact match to (or a prefix of) the desc field of the WFDB_Siginfo object that describes a matching signal.

char *units

a pointer to a null-terminated string without embedded whitespace. This field specifies the physical units of signals to which the calibration specifications apply. Usually, the units field of a WFDB_Calinfo structure must exactly match the units field of the WFDB_Siginfo structure that describes a matching signal.

double scale

the customary plotting scale, in physical units per centimeter. WFDB applications that produce graphical output may use scale as a default. Except in unusual circumstances, signals of different types should be plotted at equal multiples of their respective scales.

double low
double high

values (in physical units) corresponding to the low and high levels of a calibration pulse. If the signal is AC-coupled (see below), low is zero, and high is the pulse amplitude.

int caltype

a small integer that specifies the shape of the calibration pulse (see ‘<wfdb/wfdb.h>’ for definitions). caltype is even if signals of the corresponding sigtype are AC-coupled, and odd if they are DC-coupled.

The calibration list is a memory-resident linked list of WFDB_Calinfo structures. It is accessible only via calopen, getcal, putcal, newcal, and flushcal.


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George B. Moody (george@mit.edu)