[time-nuts] Thunderbolt performance vs temperature sensor
SAIDJACK at aol.com
SAIDJACK at aol.com
Fri Mar 6 22:17:50 UTC 2009
Hi,
while this is good news for Trimble's competition and may open up the avenue
for an amateur mod, I think we would have to be fair to Trimble and do the
double-blind test:
1) Put the original temp sensor back into the unit, let it run one week, and
do the drift tests exactly the same as before.
2) remove the sensor completely from the board, and let it run without any
sensor (if the unit works this way)
You may have seen the performance difference due to measurement errors,
aging of the crystal, ambient temperature changes (there was over 1 week
difference between the two tests, so I am sure ambient temperature effects were
different on the two runs), etc.
To really get to the bottom of this, you would have to put the unit into a
thermal chamber and cycle it from say -20C to +60C over an hour with say 10C
steps and see the frequency change versus temperature.
bye,
Said
In a message dated 3/6/2009 09:58:07 Pacific Standard Time,
holrum at hotmail.com writes:
So, it appears that the Thunderbolt does indeed use the temperature sensor
readings in its disciplining of the oscillator (which is also obvious from
the plots of DAC voltage vs temperature) and that the units performance (at
least the holdover performance) was adversely affected when the DS1620
temperature sensor chip was changed going from rev D to rev E.
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