[time-nuts] Strange temperature peak

Alberto di Bene dibene at usa.net
Sat May 28 15:37:38 UTC 2011


   On 5/27/2011 10:58 PM, WarrenS wrote:

The Tbolt uses a special method to get high resolution data from its
temperature sensor by combining three things.
The first is the sensor's standard data output which is used for the most
significant bits. This gives about 1 deg resolution.
2nd an internal register is used for the middle bits which gives resolution
of 0.009 deg
and then the Tbolt's firmware averages the internal register data to get the
LS bits, with resolution (not accuracy) below 0.001 deg.

   On 5/28/2011 4:12 AM, Mark Sims wrote:

The spikes are due to an artifact in the way the Tbolt firmware reads the
temperature sensor chip.  It reads two registers and combine the values to
get a high-res temp reading.  But if the firmware accesses the registers
in-between the time that the temp sensor chip updates them it can produce
a bogus value.  Typically this seems to happen on average of once every couple o
f hours.

   Warren and Mark,
      thanks indeed. This explains everything, and also some other
   idiosyncrasies I had noticed in the
   temperature graph display.
   All clear now  :-)
   73  Alberto  I2PHD


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