From: CFKinsey@military.org.jp   
      
   On Thu, 25 Jun 2020 02:31:23 +0100, whit3rd  wrote:   
      
   > On Wednesday, June 24, 2020 at 1:03:56 PM UTC-7, Rich wrote:   
   >> In sci.electronics.equipment Commander Kinsey    
   wrote:   
   >> > I just bought an amp clamp meter, and it states the error is "+/-   
   >> > 1.9% + 3 digits".  What does the "3 digits" part mean?   
   >>   
   >> The "3 digits" part is a measure of absolute error (i.e., the amount of   
   >> error that does not depend upon the magnitude of the value being   
   >> measured).  The percentage part is a measure of relative error (i.e.,   
   >> the amount of error that does depend upon the magnitude of the value   
   >> being measured).   
   >   
   > That's not the whole story; the percentage part is often a percentage   
   > of the FULL RANGE to which the instrument is switched.   It represents some   
   > absolute errors (offset voltages) which include  slow drifts.   Resolution   
   > in excess of that percentage error is useful only in close-timed   
   determinations   
   > relative to the amplifier or reference drift and ageing.   
      
   How do I know which one the % error refers to, as I've never seen it stated in   
   the instructions?  That would make a big difference if I was reading 0.4 amps   
   on a 10 amp range.   
      
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