Bruce, I have been thinking about the DS18B20 with programmable resolution.
Best regards Ulrich > -----Ursprungliche Nachricht----- > Von: [email protected] > [mailto:[email protected]] Im Auftrag von Bruce Griffiths > Gesendet: Donnerstag, 5. Februar 2009 12:14 > An: Discussion of precise time and frequency measurement > Betreff: Re: [time-nuts] Tbolt temperature sensor > > > Ulrich > > As in the difference between the DS620 (10, 11, 12, or 13 bit > directly with no additional calculation) and the DS1620 (9 > bits + 3bits extension via the procedure in the datasheet)? > > The original post did state that the sensor was a DS1620. > Mark also stated in a later post that he had replaced the > chip a new DS1620 with no effect on the resolution of the > reported temperature. > > Bruce > > Ulrich Bangert wrote: > > 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.
