Gents, 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. Best regards Ulrich Bnagert > -----Ursprungliche Nachricht----- > Von: [email protected] > [mailto:[email protected]] Im Auftrag von [email protected] > Gesendet: Donnerstag, 5. Februar 2009 11:15 > An: [email protected] > Betreff: Re: [time-nuts] Tbolt temperature sensor > > > > In a message dated 05/02/2009 06:25:52 GMT Standard Time, > [email protected] > writes: > > 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 > itself. > > regards > > Nigel > GM8PZR > > regards > > Nigel > GM8PZR > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts > and > follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
