Source: record apnea-ecg/a02
val has 1 row (signal) and 3182000 columns (samples/signal)
Duration:  8:50:20
Sampling frequency: 100 Hz  Sampling interval: 0.01 sec
Row	Signal	Gain	Base	Units
1	ECG	200	0	mV

To convert from raw units to the physical units shown
above, subtract 'base' and divide by 'gain'.
