Power Grid Freq Variations To Be Allowed

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On 6/28/2011 4:38 PM, Mark Lloyd wrote:

There are always the computer implant augmented brains to contend with in the future. I think Star Trek The Next Generation had some little folks called Binars who were computer experts because they had all sorts of computer parts implanted in their bodies. :-)
TDD
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Okay, I've been good and have managed to keep myself under control. But I am officially breaking down under the strain of respectability and asking, when is the first time a person in the control room will turn to another and ask: "What's the frequency, Kenneth?" I feel MUCH better now.
--
People thought cybersex was a safe alternative,
until patients started presenting with sexually
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First it's Casablanca references, then Dan Rather. Do you think you're in some arty-farty culture group?
(-:
I believe they said "Kenneth, what is the frequency?" when they beat him. My guess? Timecops, pre-punishing him for the Bush ANG debacle.
Back to reality: What bothers me most about the frequency thing is their attitude: "Let's just do it and see if anyone complains." Seems a little cavalier.
-- Bobby G.
-- Bobby G.
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wrote:

Ah yes! I remember the stunning brunette Minuette (sp?) on the holodeck who obviously found a materializer and a time machine and came back to Earth to be the psychiatrist on the Lawn Order series of procedural police dramas.
-- Bobby G.
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On 6/28/2011 8:13 PM, Robert Green wrote:

I started reading SciFi books when when I was a little kid and I've been hooked ever since. The episode was "11001001" and the babe on the holodeck who captivated Riker was "Minuet". That episode first aired in February of 1988, DANG! it's been a long time. ^_^
TDD
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dpb wrote:

Even the newer / better turntables don't rely on line frequency, they have crystal references and servo loops to maintain accurate speed even with varying loading.
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On 6/26/2011 2:01 PM, Pete C. wrote:

he was probably referring to the old direct drive models that had a neon light and hash marks on the edge that you used to set the proper speed.
--
Steve Barker
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harry wrote:

The difference between 60 and 60.5 Hz is 14 cents, to the nearest cent. There are 1200 cents in an octave, 100 in a semitone.
I have heard songs on the radio sounding sharp when they were played 2% fast - 34 cents. Those with good "perfect pitch" can hear if a whole musical performance is 14 cents off.
In comparison between two slightly different tones, 4 cents is often audible, 3 cents sometimes is. 3 cents is a frequency difference of .17%.
--
- Don Klipstein ( snipped-for-privacy@donklipstein.com)

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On 06/25/2011 03:29 PM, HeyBub wrote:

And frequency stability is different from long-term time accuracy.
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HeyBub wrote:

I take it you haven't looked at a computer since the '70s. There hasn't been a computer power supply that cared about line frequency in decades, most these days don't care about line voltage either.
I doubt that there are any synchronous motor based traffic light controls left in use anywhere in the US either. The only places rural enough to have such old controllers are also too rural to have traffic lights.
I don't recall ever seeing a security system that cared about line frequency either, all they care about is if there is line power present.
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Ah, no...
Anyone who has a device with a crystal oscillator timebase knows that the device has to be reset to the correct time occasionally. On the other hand, plug-in devices that use the 60 Hz signal for the timebase have been (up until now) essentially perfect since the signal has been manually twiddled to make it so. (There is actually a 10 second tolerance in the East, less in the West.) And implementation is dirt cheap: you capacitively couple to the power line, use a Schmitt trigger, and some divide-by-60 counters. With better performance at less cost, using the power-line frequency as a reference is the preferred method.
Thing become ambiguous in plug-in devices with "battery backup." These devices do have crystal oscillators to ride out the power outage. When the power is on they can either use the crystal oscillator as reference, or the power line as reference, however the device was designed.
- Jonathan
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You are the first poster to actually get it correct. Thanks!!!
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wrote:

That hasn't been an accurate statement for quit some time. Whole clocks can be built for the cost of the circuitry involved of syncing the clock to to the power line. Oscillators built into the clock IC are more than accurate enough to maintain accurate clock time over years. Case in point, my trucks clock, 2003 Nissan bought in fall of 2002. Clock has never been set except by the dealer. It is now about 30 seconds off and it has always been about 30 seconds off per my cellphone clock. I never bother correcting it for DST. The Design of clocks Jonathan is talking about used an RC oscillator that was synced to the power line. By design the oscillator was a little slow, this made syncing it to the power line signal easier. Also have a desk clock meant to run on a aaa or aaaa battery but I now have it wired into 4 D cells in parallel. It has maintained accuracy for years also.
Jimmie
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Seems like the variation allowed, the more variation syncing is problematic. The whole grid is always loosing power to all the stations producing slight variation pulling on each other.
Crystals tend to be stable, but there are times when the crystal makes a steep, then needs to be calibrated. A primary frequency standard uses a quartz oscillator with another correction loop like from cesium standard.
Greg
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"Gz" wrote in message wrote: --------snip-------- Seems like the variation allowed, the more variation syncing is problematic. The whole grid is always loosing power to all the stations producing slight variation pulling on each other. ------- Not really:
a)synchronizing is matching an incoming generator to the grid frequency, voltage and phase. Normal variations in these are not a problem- if they are, then there are more serious problems occuring.
b)There is power transfer between machines- the resultant forces act to pull all machines to the same frequency. You can't run one machine at 60Hz and another at 60.1 Hz. However, the system transmission losses, for short periods of time, may increase or decrease slightly. It averages out.
c) Not correcting time as often will not adversely affect operation of the system - all it means is that there may be (not will be) some more time error before correction. This is really not a big issue.
Don Kelly cross out to reply
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There are, and I have built devices with rudimentary oscillators that sync with the line, but are not so precise, like 555 timers.
Greg
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In article

I must have lucked out. For about $30 I bought a Pulsar wrist watch at least 15 years ago. I estimate its stability as about one or two parts in 10^7 as long as the temperature does not have extreme deviations. I only reset it when I need to change for daylight savings time or for a new cell. It is about four seconds fast this now. That may be because of the cell having been in the watch for over two years now and it is probably going to fail soon.
--

Sam

Conservatives are against Darwinism but for natural selection.
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On 6/25/2011 22:28 PM, Salmon Egg wrote:

An interesting story, some of the early crystal watches had their accuracy tied to maintaining the crystal temperature. By accounting for the watch being on a human's wrist, the designers were able to design for a specific temperature at the back of the watch.
In some old power plants, we had ovens to maintain the crystal temperature of our frequency base. But curiously, the frequency base was not used for controlling the generator (base-load plant), only the oscillograph for transient plots.
daestrom
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wrote:

all crystal timebases rely on constant temp for accuracy. if the crystal temp varies,the crystal freq varies.That's physics. Temp-compensated xtal oscillators(TXCO's) rely on opposing R and C temp coefficients to compensate somewhat for temp variations. KEYWORD;"somewhat". it's not 100% effective.

These days,they use atomic clocks for precise freq reference. like Rubidium oscillators,cesium,or quantum methods.
http://www.nist.gov/pml/div688/grp50/primary-frequency-standards.cfm
--
Jim Yanik
jyanik
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On 6/26/2011 11:56 AM, daestrom wrote:

A lot of the test equipment from the big old name brand manufacturers had crystal ovens inside for the time base circuitry when I worked a bench tech in a repair depot 30 years ago. Like gold boat anchors and just as expensive. :-)
TDD
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