How do i know what is the correct time?
Discussion
I ask this as i have noticed that am/fm and DAB broadcasts of thes ame channel are about 4 secs out
Also when i swap from digital tele to HD that is 'out' as well
so which of these is the right time according to the good old 'speaking clock'
And how accurate is the 'computer clock' websites?
Also when i swap from digital tele to HD that is 'out' as well
so which of these is the right time according to the good old 'speaking clock'
And how accurate is the 'computer clock' websites?
silverfoxcc said:
I ask this as i have noticed that am/fm and DAB broadcasts of thes ame channel are about 4 secs out
Also when i swap from digital tele to HD that is 'out' as well
so which of these is the right time according to the good old 'speaking clock'
And how accurate is the 'computer clock' websites?
DAB broadcasts are out of sync by about 4-6 seconds due to the encoding and decoding process. Want to use the Radio 2 pips? Go with analogue.Also when i swap from digital tele to HD that is 'out' as well
so which of these is the right time according to the good old 'speaking clock'
And how accurate is the 'computer clock' websites?
https://time.is/
' The displayed time will normally have a precision of 0.02-0.10 seconds. '
Will also show you how far out your computer clock is.
For a desktop clock, the now cheap 'atomic' radio controlled clocks which sync to long wave transmissions are good, as they also update during BST/UTC transitions ( summer/winter time) and the date is also included in the transmissions so they update during Leap years.
These are £3 and excellent:
https://www.amazon.co.uk/Controlled-Backlight-Func...
GPS derived time is also close enough for many human-based occupations.
GMT was replaced by UTC in 1972. The BBC seem keen to keep referring to it, as UTC is a bit 'European'.
The Greenwich Meridian was defined by a USA/European conference in Washington DC in 1884 at the request of USA president Chester Alan Arthur. It's as British as baked beans.
The Prime Meridian also runs through Cleethorpes, but Cleethorpes Mean Time has so far failed to catch on.
You could just look at a mobile phone...
' The displayed time will normally have a precision of 0.02-0.10 seconds. '
Will also show you how far out your computer clock is.
For a desktop clock, the now cheap 'atomic' radio controlled clocks which sync to long wave transmissions are good, as they also update during BST/UTC transitions ( summer/winter time) and the date is also included in the transmissions so they update during Leap years.
These are £3 and excellent:
https://www.amazon.co.uk/Controlled-Backlight-Func...
GPS derived time is also close enough for many human-based occupations.
GMT was replaced by UTC in 1972. The BBC seem keen to keep referring to it, as UTC is a bit 'European'.
The Greenwich Meridian was defined by a USA/European conference in Washington DC in 1884 at the request of USA president Chester Alan Arthur. It's as British as baked beans.
The Prime Meridian also runs through Cleethorpes, but Cleethorpes Mean Time has so far failed to catch on.
You could just look at a mobile phone...
Mr E said:
Robbidoo said:
Use an NTP server
Use a stratum 1 NTP server if it’s important. Use gps for everything else.
In contrast NTP has to operate across a network intermediated by lots of routers that are each going to add some random delay determined by whatever other traffic they happen to be processing. If pings take 10s of milliseconds, I can't see the accuracy getting better than 1ms.
As said, I'm speaking from a position of ignorance, so would be very interested to hear an explanation.
Edited by ATG on Thursday 11th October 11:50
BuzzBravado said:
Isn't it true there is only one genuine atomic clock in the world, and that is the only true definition of time.
No, it's a definition (mean) derived from many atomic clocks around the world. Also Mean times are 'constructed' times and there are many other standards. Time nerd-O-rama here:
https://en.wikipedia.org/wiki/Time_standard
daddy cool said:
My G-Shock Rangeman picks up a radio signal every morning from the atomic clock at NPL.
Its accurate to about +/- 1 second every 138 million years, but for the price I paid i'll put up with that level of inaccuracy.
The radio controlled clocks are accurate enough for most humans. :-) Its accurate to about +/- 1 second every 138 million years, but for the price I paid i'll put up with that level of inaccuracy.
The NPL 'MSF' signal transmitters and caesium clocks were moved to Anthorn, Cumbria some time ago. Occasionally, they let interested parties in for a tour.
The 'atomic clocks' here get their signals from Mainflingen, south-east of Frankfurt , callsign DCF77. It's defined as 'German National Legal Time' - GNLT. The signal is good throughout South-East England.
We now have quartz watch movements accurate to 10 or 12 seconds a year for about £100. The accuracy tends to fail twice a year when we have to change them through BST/UTC.
There are smartphone apps which contact Tier 1 timeservers, (or use GPS time) this one is hooked up the National Physical Labs, and used for double checking server/network clocks. Our PC clocks are frequently more than three minutes out.
Feel free to use the picture to set your watch. :-)
ATG said:
From a position of complete ignorance, I'd expect GPS to be by far the most accurate. GPS satellites are effectively just extremely accurate clocks that know where they are and are broadcasting their location and the time. The GPS receiver knows how long it takes the satellite's signal to travel from the satellite to the receiver to within a few metres at the speed of light. The receiver should be able to figure out the time to within a few 100 nano seconds.
The clock in my car (older Mercedes) is apparently sync'd to GPS time and is, as best you can tell by eye, spot-on to the 6th pip of the BBC time signal (on FM).
I set my watch by www.timeanddate.com and it's always spot on when comparing it to Edinburgh Castle's One o'clock Gun - good enough for me!
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