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#60640 - 01/08/06 03:47 AM Master Clocks  
RODALCO  Offline
Joined: Dec 2005
Posts: 854
Titirangi, Akld, New Zealand
Who in the electrical industry works or maintains master, slave clock systems.

Ok I admit it's part of a hobby of mine but interesting to know if new systems are being installed now these days, or is everything going the way of cheap quarz clocks showing all different times in public buildings.

I maintained the old WEPB English clock systems ½ second pendulum master clock with about 30 'slaves' in the Henderson POCO depot. output was 24 volts dc for about 2 seconds with polarity change every minute to provide the pulse to the 'slaves'.

There were some very intersting systems on the older pendulum clocks like the Hipp Toggle on the FAVAG masterclocks which provided a direct drive to the pendulum.
Also the outputs to the 'slaves' was via contacts, relays or mercury switches.

The newer masterclocks are obviously electronic and pick up a timereference from a time transmitter like Frankfürt DCF in Germany or via accurate quarz crytals.

It would be very interesting to see through ECN what still going on in this specialized field of electric timekeeping.

Looking forward to your replies

Thanks Raymond alias RODALCO

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#60641 - 01/08/06 04:53 AM Re: Master Clocks  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
I installed a master clock system in a insurance company building about 8 years ago.

It was nothing like the old master clock system.

It has Large LED displays and is controlled via it's own LAN (Local Area Network)

It was a nice system and it could be interconnected with other building systems like the fire alarm so the display would change from the time to flashing "FIRE".

Anyway I doubt we will see that type of master clock system in the future as 'controlled' clocks are cheap and easy.

Beside me on the wall now is a Analog clock that once an hour verifies the time via radio signal from NIST in Colorado USA.

WWVB atomic clock receiver

A radio system is available in North America set up and operated by NIST - the National Institute of Standards and Technology, located in Fort Collins, Colorado. NIST operates radio station WWVB, which is the station that transmits the time codes. WWVB has high transmitter power (50,000 watts), a very efficient antenna and an extremely low frequency (60,000 Hz). For comparison, a typical AM radio station broadcasts at a frequency of 1,000,000 Hz. The combination of high power and low frequency gives the radio waves from WWVB a lot of bounce, and this single station can therefore cover the entire continental United States plus much of Canada and Central America. The time codes are sent from WWVB using one of the simplest systems possible, and at a very low data rate of one bit per second. The 60,000 Hz signal is always transmitted, but every second it is significantly reduced in power for a period of 0.2, 0.5 or 0.8 seconds: • 0.2 seconds of reduced power means a binary zero • 0.5 seconds of reduced power is a binary one. • 0.8 seconds of reduced power is a separator. The time code is sent in BCD (Binary Coded Decimal) and indicates minutes, hours, day of the year and year, along with information about daylight savings time and leap years. The time is transmitted using 53 bits and 7 separators, and therefore takes 60 seconds to transmit. A clock or watch can contain an extremely small and relatively simple antenna and receiver to decode the information in the signal and set the clock's time accurately. All that you have to do is set the time zone, and the atomic clock will display the correct time.

I think my clock cost less than $20.00 and no wiring was needed.


Bob Badger
Construction & Maintenance Electrician

#60642 - 01/08/06 07:21 AM Re: Master Clocks  
frank  Offline
Joined: May 2001
Posts: 376
windsor ontario canada
We are in the process of installing the new PRIMIS GPS system.The slaves run 5yrs on regular batteries and the master is on the roof.It downloads information from a satellite and automatically updates as necessary.once it's setup everything is totaly autonomous.We currently have the 1962 vintage Edwards systems with two masters and about 150 slaves

[This message has been edited by frank (edited 01-08-2006).]

#60643 - 01/08/06 11:10 AM Re: Master Clocks  
JoeTestingEngr  Offline
Joined: Nov 2005
Posts: 791
Chicago, Il.
Most SCADA systems (Supervisory Control And Data Acquisition) provide a means of the Master end sending a time sync signal to all the remotes in the field. The Master can get its reference from WWVB, GPS, or other means. The remotes can then send time-stamped data back to the Master. We don't use this scheme so our data come back referenced to the time that a given RTU was polled, perhaps several seconds after a status or analog change outside of the deadband.

Our Master is sometines referenced within a second to WWVB. This happens when Power Control gives me a call about the SCADA clock needing set. I look at my WWVB referenced watch and correct the Master from my desktop. But again, when your acquired data might be time stamped several seconds late, fractions of a second accuracy of a Master doesn't gain you anything. Have you ever heard a news report of a train derailing or storm damage causing service interruptions at 09:15:27.3 hours? I didn't think so.

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