I set up my spark core to log for several days and graphed the results.  The data coming from my temperature sensor was very noisy.  I added some filtering caps, but to no avail.  After examining the datasheet more carefully I discovered that a +/- 2 C range is normal, which is much greater than I would like.  I ordered some new sensors which should have a +/- 0.33 C variance at room temperature, which should give much better results.