[time-nuts] Tbolt temperature sensor
df6jb at ulrich-bangert.de
Thu Feb 5 10:23:44 UTC 2009
has anyone checked which DALLAS part is REALLY inside the box?
I put forward this question because DALLAS has parts in their portfolio
that sell as "genuine" 12-bit resolution ones and other ones that sell
as 9-bit resolution ones where additional 3 bits of resolution can be
used by some "tricks" The software for these two types is NOT the same.
> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von GandalfG8 at aol.com
> Gesendet: Donnerstag, 5. Februar 2009 11:15
> An: time-nuts at febo.com
> Betreff: Re: [time-nuts] Tbolt temperature sensor
> In a message dated 05/02/2009 06:25:52 GMT Standard Time,
> holrum at hotmail.com
> Actually, what is apparently going on with the newer
> Thunderbolts is worse
> than that. The reported temperature seems to only end in
> 0.25C or 0.75C, so
> it has an effective 0.5C resolution. The basic DS1620
> resolution is 9
> bits, but the Tbolt firmware reduces that to 8 bits since
> the first step in the
> high res temp algorithm is to mask off the lower bit.
> Whatever is going on
> they are not getting the extra resolution that they think
> they are, and in
> fact they are reducing the basic resolution of the chip.
> The firmware does seem do do some filtering on those values
> since whenever
> the reading steps you can see some smoothing going on. A
> lot of times the
> temperature value oscillatates around the step point. The
> filter apparently
> does not have any hysteresis.
> The older Thunderbolts produced a nice smooth curve. The high res
> temperature reading (Bruce says is 12 bit/0.0625C) coupled
> with the firmware filtering
> gave temperature curves with microdegree scale resolution.
> The newer ones
> clunk around with effectively 0.5C resolution.
> But have you actually established this has anything
> whatsoever to do with
> the oscillator conditioning and, if not, what effects are you
> suggesting it has
> on the conditioned output?
> Isn't it likely that a temperature sensor adjacent to the
> RS232 connector is
> just going to monitor unit temperature for environmental
> purposes, perhaps,
> for example, to give the option for flagging up an
> overheating situation, in
> which case surely 0.5C resolution is more than adequate and
> the "clunkiness"
> isn't really an issue?
> I agree it's always nice to know what's happening, and why,
> but I suspect
> the performance of this sensor has no relevance to the
> oscillator performance
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts
> follow the instructions there.
More information about the time-nuts