On 2015-02-19, Rob <nom...@example.com> wrote: > Miroslav Lichvar <mlich...@redhat.com> wrote: >> On Thu, Feb 19, 2015 at 12:48:46PM +0000, Rob wrote: >>> I am still finding out what sensor is best to use, we do have a room >>> temperature sensor that has .1C resolution and is readable via snmp, >>> and there are the usual sensors for board- and inlet air temperature. >>> (and of course CPU temperature) >>> >>> It does not matter if it is only a course indication, the room temperature >>> varies over a -10 .. 50C range (don't ask...) and a 1C resolution is not >>> bad relative to that. >> >> In my tests using a sensor with 1C resolution it was barely useful >> with NTP sources and 1024s polling interval. If the sensitivity is >> around 0.1 ppm per degree, 1C resolution means the compensation >> jumping the frequency in 0.1ppm steps. That's a lot, especially if you >> compare it to the tracking skew with a refclock. > > Ok but of course we are using PPS and a 16 second polling interval. > (or maybe the PPS refclock polls even faster although it displays 4 as > the poll interval indicator)
The shm refclock will get one pulse per second, and then average the offsets over a 16 sec period after getting rid of the outliers. _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
