Process timer using atomic clock as standard

rich p · Jun 29, 2017

We have a master stop watch we use to check accuracy on our process timers. We always use the Atomic clock for calibrating using this website https://www.time.gov/
The issue I have is I don't have any documentation from the Atomic clock. I googled for any NIST certificate but came up empty. Can anyone tell me how they are doing this? Thanks for any help.

Red James · Jun 29, 2017

Poor choice of standard, as web traffic does not travel instantaneous along the many pathways of the web. Look for certs from the makers of your master stop watch.

rich p · Jun 29, 2017

Thanks for reply. That makes sense. Has anyone used one of these? 53 Traceable(R) Atomic Clock

bryan_machine · Jun 29, 2017

"radio-controlled" link to NIST's atomic clock in boulder, CO. This implies it's listening to the radio station (WWV I think) which broadcasts the time. www.time.gov has an app with the same data, and there is also a web protocol, supported by various time servers.

Calling that an "atomic clock" seems like a fraud - real atomic clocks (like cesium) are rather bigger.

It would seem the best modern solution is GPS.

But why do you care? All of this is about time of day, not length of time per se. And an ordinary quartz clock can be Very Very good.

DDoug · Jun 29, 2017

I dunno but at the radio/tv station, we would tune in WWV, and set our clocks
so we would be synced to network.

Boy oh boy did I hate Saturday night 6:00 pm Garrison Keeler, would always
come up late.....man did a couple of seconds of dead air make me sweat.

greif1 · Jul 5, 2017

You can get time from WWV by shortwave radio (accuracy 1/100 second (10ms) or better), or call their service on the phone (land line- cell might be different) for 150ms accuracy)

https://www.nist.gov/pml/time-and-f...adcasts-frequently-asked-questions-faq#listen

When I listen to WWV or WWVH, how accurate is the time?
The time is kept to within less than 0.0001 milliseconds of Coordinated Universal Time (UTC) at the transmitter site, but the signal is delayed as it travels from the radio station to your location. This delay increases the further that you are from the station, and the delay can vary by as much as 1 millisecond if the signal is bouncing between Earth and the ionosphere. However, for most users in the United States, the received accuracy should be less than 10 milliseconds (1/100 of a second).
Listening to the signals by telephone, the delays will be larger, but the time is usually accurate to within 30 milliseconds if you are using a landline. If you are using a cellular phone or a voice over Internet protocol (VOIP) connection, the delay can be much larger, but should still not exceed 150 milliseconds, based on International Telecommunication Union (ITU) recommendations for voice transmissions.

The real Leigh · Jul 5, 2017

bryan_machine said:
"radio-controlled" link to NIST's atomic clock in boulder, CO. This implies it's listening to the radio station (WWV I think) which broadcasts the time.

These "atomic clocks" listen to WWVB on 60 kHz, way below the broadcast band.

It transmits a very accurate time code that's usable in most of the USA.

I have such a clock on the wall above my desk.
It syncs with WWVB at about midnight every day.

- Leigh

greif1 · Jul 6, 2017

This fellow is looking for a standard to check an interval (his stopwatch), not time of day. Getting an atomic clock involved opens the door to question how good it is and how good it is at times other than when it is synced.

If he uses time ticks directly from NIST (via phone or radio), there is little left to question accuracy and traceability.

tomato coupe · Jul 6, 2017

If the OP is using an actual stopwatch, then using an atomic clock as a reference is complete overkill. The accuracy of his measurements will be totally dependent on how well he can synchronize his "thumb" to the event he is measuring.

greif1 · Jul 12, 2017

Overkill yes, but he still needs to establish traceability.

Chip Chester · Jul 12, 2017

An alternative with general availability and interfacing docs would be video/broadcast industry timecode generators that are linked to GPS receivers... which would at least be traceable. Whether it's to the standards required remains to be seen. Of course, there are likely just GPS receiver modules with enough documentation to address his needs, too.

(The various broadcast networks each have a different idea of when "6:00" really is. They know they're early or late, but there are too many affiliates down the chain that have done it the old way for too many years for them to change to 'correct' time.)

Chip

Tony Quiring · Jul 12, 2017

Many ways and only limited by budget.

Cell phones need dead on accuracy so data does not get wonky between cells and gps is the tool used.

The little cone antennas at ground level you see at the cell towers serve this function.

They like consumer atomic clocks (wwv reference) have their own frequency standard that uses the gps for reference and will operate without gps for a few days.

Telco switch rooms sometimes use gps but also used is a standard T1 line as it needs to be stable.

For general consumer use one should look at time keeping systems as they need accuracy to some point and there are already in place network clocks that use a standard located someplace via the net and via magic of computing can compensate for all of the distributed latency of the systems between wherever the standard is and the end user.

Example is watching video on a current mobile device while moving in a market with proper cell tower density and bandwidth.

The video is sliced up into thousands of chunks going out of multiple cell towers that are different distances from the end user but the device can put them all back together and show it without glitches.

What you want is simple.

Google network clock to start and you will find your answer

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greif1 · Jul 12, 2017

Let's not forget that to be traceable it has to stand up to an audit. Signal directly from NIST- no problem; signal from various other places which have no documentation showing traceability = problem. Spec sheets do not = traceability.

Tony Quiring · Jul 12, 2017

Working at a public safety dispatch center and here is what they have.

It is a set of equipment from Spectracom and is gps based with an assortment of interfaces.

Photos will be on following posts.

NetClock GPS/ 9383 and TimeSaver 9388

{ad deleted - TRL}

Tony Quiring · Jul 12, 2017

Photos below.

This is older equupment but it should be a starting point.

{ad deleted - TRL}

MattiJ · Jul 17, 2017

Easiest and lowest cost solution with best possibility to pass even most idiotic auditors is digital stopwatch calibrated yearly at ISO 17025 accredited cal lab.

edit: forgot to add that if the auditor is both idiot AND american its best to have the traceability to NIST.

greif1 · Jul 18, 2017

Traceable stopwatch! Even better solution! You can buy one with docs here for ~$46;
Stopwatches

comes with;
TRACEABLE® CERTIFICATE
An individually-numbered Traceable® Certificate provided with each unit, assures accuracy from our ISO/IEC 17025:2005 (1750.01) calibration laboratory accredited by A2LA. It indicates traceability of measurements to the SI units through NIST or other recognized national measurement institutes (NMI) that are signatories to the CIPM Mutual Recognition Agreement.

Paolo_MD · Jul 18, 2017

Tony Quiring said:
...
Example is watching video on a current mobile device while moving in a market with proper cell tower density and bandwidth.

The video is sliced up into thousands of chunks going out of multiple cell towers that are different distances from the end user but the device can put them all back together and show it without glitches.

What you want is simple.

Google network clock to start and you will find your answer

{ad deleted - TRL}

Have you ever heard about "buffering"? That's what you have when streaming video on practically any device: since not necessarily all the "packets" of data that you receive from one or more sources are correct and sometimes they need to be sent again, any streaming media is played back with a delay: the better the connection, the shorter the delay.

For most of the other things, especially GPS functions, cell phones need accurate time either directly from GPS satellites or through the cell towers.

Paolo

dcsipo · Jul 18, 2017

what precision do you need?

Network Time Protocol - Wikipedia

dee
;-D

The real Leigh · Jul 18, 2017

Frequency and Time, which is the inverse of Frequency, can be measured with greater precision than any other physical quantity.
Parts in 10E-11 (0.00000000001) or better are easily achieved with modern laboratory equipment.

That does NOT translate to the accuracy of a stopwatch when used as intended.

The problem is the human reaction time involved in such measurements.

Contrast this with a micrometer. When used with a ratchet or friction tensioning device, different users should get the same readings within a very narrow range. No such uniformity is true for stopwatches.

- Leigh

Process timer using atomic clock as standard

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