HEM 712C USED TO TRACK A-FIB I HAVE USED 3 UNITS OVER THE PAST 2 YEARS. I have been working on the data that sometimes shows no variability in hart rate for days or hours. My Dr. insist it is always in A-Fib. Is it possible that a calibration error may be variable? There are lots of types of hart irregularity to consider. I am wondering if (not detected), is machine error. Unfortunately my pacemaker was only installed with one lead, so no standard deviation data exists. Very few ERROR messages appear this year, which I assume is cuff position error: Pump speed may vary a bit