[time-nuts] Tbolt temperature sensor

Mark Sims holrum at hotmail.com
Thu Feb 5 00:03:29 UTC 2009

Hello Tom,

All my earlier Tbolts report 2002-2003 manufacturing date codes.  They are rev 2.22 and 3.00 firmware.  They all show the nice smooth high res temperature curves that are usually sinusoidal.   I know of around a dozen units that respond this way.

All the later build Tbolts that I have seen (mine,  Asa's,  and one other) are from the March to May 2005 time frame.  They all show the basically flat temperature curve that is quantized to 0.25/0.75C readings (except when a firmware filter kicks in for a short time when the value steps between readings).

The temperature sensor chip is a DS1620 chip in a small SOIC-8 package next to the RS-232 connector.  I guess the questions are:

1) Is the difference a firmware change (even though the "problem" units all report the same 3.0 firmware levels as the earlier units) or is it a change in the sensor chip that  causes the high-res temperature read technique listed in the DS1620 data sheet to fail on the Tbolts?

2) Which units are affected by the issue?   Can it be isolated to a date code or some other marking on the DS1620 package?  Is there a Tbolt manufacturing date or range where the issue first pops up or occurs over?  

Lady Heather shows the Tbolt manufacturing dates and firmware dates.   She also plots the temperature curve. 
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