On Thu, Jun 30, 2011 at 1:20 PM, RussellMc wrote: > > I suggested Sigma-Delta as an option, [having had too much (bad) > experience with software versions]. With IC based versions the > manufacturer (presumably) has sorted out the interesting things that > can happen. > > I've never seen someone use two-layer parenthesis in their email. I guess there's a first time for everything. I know that you suggested it. I just wanted to add my experience. I just finished a production tester that uses this as a method of measuring curren= t consumption down to the microamp range so I know it works pretty well. > Main issue with the MCP3551 is conversion time a bit over 70 mS or > say 14 conversions per second. > That easily exceeds his "several per second" OK and falls short of the > 100 per second 'great". > At 20 bits the tradeoff is acceptable. > > MCP3553 is 17 milliseconds woth no price difference. > > MCP3551 is notional 22 bits while MCP3553 is 20 bits and (much) more > than adequate. > > > Right, it's 22 bits - "21.9" but 1 is for input polarity which is useless for measuring supply current in most cases. As an alternative I've used a transimpedance amplifier across a shunt but I believe the A/D is superior. --=20 Martin K. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .