FAQ: Difference between revisions

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Revision as of 08:07, 27 March 2016

251 bytes added ,  27 March 2016
→‎... How do Fine Offset stations handle Daylight Saving Time?: Allow for radio controlled clocks in some stations
(→‎... How do Fine Offset stations handle Daylight Saving Time?: Allow for radio controlled clocks in some stations)
=== ... How do Fine Offset stations handle Daylight Saving Time? ===
 
*For Fine Offset stationsmodels ''without access to a radio controlled clock'', if you don't have Cumulus running when DST ends in autumn, then when you start Cumulus up again, the catch up ''misses off the first hour after the time Cumulus was stopped'' (unless you have adjusted the time in [[today.ini]] by subtracting one hour for end of DST while Cumulus was stopped).
**This is because the console memory does not time-stamp the data blocks and Cumulus does not remember the console data block used just before shutdown, (after all depending on how long Cumulus has been stopped and the station logging interval, the oldeach memory location couldsimply becontains overwrittenthe bynumber now), but each memory location does containsof minutes elapsed since the previous memory location usedwas last updated.
**Cumulus does not remember the console data block used just before shutdown, (after all depending on how long Cumulus has been stopped and the station logging interval, the old memory location could be overwritten by now), and so Cumulus works out a time-stamp based on current clock time and the stored elapsed interval times as it works back through those memory locations.
**The stored minutes elapsed value will be consistent with the logging interval you selected for the station (might be different to that selected on Cumulus) and apart from adding an extra minute if a read from the transmitter (every 48 seconds on models without solar sensors) delays a particular log update, the console clock is unaware of DST.
**On restart Cumulus just tries to read the appropriate number of hours worth of observations back from the block now marked as latest.
**For example if it was stopped at 2200 DST and restarted at 0600 standard time, Cumulus catches up with the last 8 hours worth of stored measurements as if going back to 2200 standard time, that means it retrieves back to 2300 DST and has forever lost the period 2200 to 2300 DST.
*So with Fine Offset stations, I strongly recommend that you leave Cumulus running at the end of DST, if at all possible, to ensure that average temperature, heating/cooling degree days, wind run, and similar calculations are accurate.
*See Fine Offset forum discussions for further information.
*At the start of DST in spring, the catch up will ''duplicate the last hour that Cumulus was previously operating'' (unless you have added one hour to the standard time stored in [[today.ini]] for start of DST while Cumulus was stopped).
**e.g. Stopping from 2200 standard time to 0600 DST the catch up goes back to 2200 DST or 2100 standard time.
**Some calculated measurements like average temperature, cooling degree days, and the like will be slightly out, but no measurement is actually lost.
 
== What formula does Cumulus use for Dew Point? ==
Sfws
5,838

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