Wire heating is very real - hence there are derating tables for selecting wire gauge for an application - ampacity. 4% change in resistance over 10°C is significant Insulation severely derates copper conductors.
I am familiar with Allegro Microsystems Hall sensors and most are temperature compensated. Hall elements change their response subsequent to mechanical strain and thermal effects cause mechanical strain. They have ways of stabilizing them. On Wed, May 14, 2014 at 11:55 PM, Lee Hart via EV <[email protected]> wrote: > Jan Steinman via EV wrote: > >> Thanks for bringing that to my attention, Peter, although ±4% for 90% of >> the typical annual temperature change here isn't TOO bad! I'm guessing >> temperature affects on battery capacity are of a similar magnitude. >> > > Keep in mind that the wire also heats up from the current flowing in it. > That causes additional errors. > > There are meters that use copper wire as the shunt; but they include a > thermistor that senses the wire temperature, and corrects the current > reading accordingly. > > > I think I like the hall-effect torus sensor better. >> > > Hall effect sensors can be very good; but they too have their sources of > error. A classic problem with hall effect sensors is zero drift. (not > reading 0 at zero amps). > > Simply measuring current isn't too bad. The real challenge is to measure > amphours. Any zero offset causes errors to accumulate. An offset error of > 0.1 amps on a 500 amp sensor (0.02%, or 1 part in 5,000) accumulates an > error of 2.4 amphours per day. > > -- > Anyone can make the simple complicated. Creativity is making the > complicated simple. -- Charles Mingus > -- > Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/ > group/NEDRA) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk [email protected] <[email protected]> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140515/c9e92d6e/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
