[time-nuts] Holdover, RTC for Pi as NTP GPS source

ewkehren ewkehren at AOL.com
Wed Nov 1 15:12:31 EDT 2017

Tbolt is a good oneBert Kehren

Sent from my Galaxy Tab® A
-------- Original message --------From: David J Taylor via time-nuts <time-nuts at febo.com> Date: 11/1/17  12:07 PM  (GMT-05:00) To: time-nuts at febo.com Subject: Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source 
From: Mark Sims

I have an analytical balance that reads down to micrograms.   The weigh 
chamber is surrounded by three layers of IR absorbing glass so that radiated 
body heat does not induce convection currents in the air.   I worked on a 
balance that had nanogram resolution (mostly wishful thinking in that spec). 
It operated in a vacuum.  30 bit mass-to-digital converters are rather 
finicky beasties.

It does not take all that good of a temperature sensor to detect changes in 
room temperature due to body heat (or fetching a beer from the fridge in the 
next room).  You are basically a 100 watt space heater... even larger for 
the more corpulent folks.

Temperature is indeed the killer.  My best Raspberry Pis for time-keeping 
are RasPi-1 and RasPi-4, both of which are in an unheated cupboard not 
exposed to sunlight, on the north side of the house with indoor patch GPS 


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Email: david-taylor at blueyonder.co.uk
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