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ACCURACY AND READING THE SCALE THE GOOD NEWS ABOUT A DMM IS THAT IT IS
BASED ON AN A/D CONVERTER.  OF COURSE, THE BAD NEWS IS THE SAME A/D
CONVERTER MAKES IT VERY DIFFICULT TO STATE THE METER ACCURACY IN JUST A FEW
WORDS.  THE ACCURACY, USUALLY EXPRESSED AS A PERCENTAGE, DEPENDS ON THE
BASIC ACCURACY OF THE REFERENCE USED IN THE A/D CONVERTER AS WELL AS THE
NUMBER OF BITS IN THE CONVERTER.  ON TOP OF THAT, THE DESIGN OF THE INPUT
CIRCUITS PLAYS A MAJOR ROLE IN THE FINAL NUMBER.  GENERALLY, THE ACTUAL
ACCURACY IS SPECIFIED FOR EACH SCALE OF THE METER.  AS YOU CAN SEE IN
FIGURE 10, THE WORD AUTO INDICATES THAT THE METER IS DOING AUTOMATIC
RANGING.  MOST, IF NOT ALL, DMMS HAVE AUTOMATIC RANGING.  THEY SET THE
SCALING TO PRODUCE THE MAXIMUM NUMBER OF DIGITS FOR THE VALUE BEING
MEASURED.  IF THE VALUE IS OVER THE ALLOWABLE RANGE, BUT BELOW THE POINT
WHERE THE METER IS DAMAGED, THE METER WILL READ OL, FOR OVERLOAD.  YOU CAN
SEE THIS IF YOU TURN THE METER TO THE OHMS BUT DO NOT CONNECT THE PROBES TO
ANYTHING.  THE METER SEES A RESISTANCE OVER THE MAXIMUM VALUE IT CAN
MEASURE, SO IT DISPLAYS OL.  ONE NICE FEATURE IS THE AUTOMATIC SENSING OF
POLARITY FOR VOLTAGE AND CURRENT.  FOR EXAMPLE, IF YOU HAD A 9 V BATTERY
AND CONNECTED THE COMMON OR BLACK TERMINAL TO THE BATTERY POSITIVE AND THE
RED TERMINAL TO THE BATTERY NEGATIVE, A MINUS SIGN WOULD APPEAR IN FRONT OF
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