On Mon, Mar 7, 2022 at 12:04 PM gene heskett <[email protected]> wrote:
> > Technically, we can do it but you'll need a couple of dump trucks full of > gold to finance one neasurement. We can't yet buy a calibrated answer in > 10 milliseconds for a $500 bill. Someday? Maybe, but it may take a new > method to be invented. > I have a system that does FAR better. I tried to build a clock that would give accurate absolute time measurements with the goal of it being inexpensive. It is easy to do this if you have boatloads of money but what if you limit the budget to about $50? So with a $50 budget, I can measure seconds of time, referenced to a world standard to 10 decimal places. 13 is possible if the budget were larger. How? First, you need a really good crystal oscillator. On this budget you have to buy them used on eBay. These will typically be double ovenized and inside some insulated temperature controled and sealed. box. They are removed from microwave telecommunications equipment or laboratory grade frequency meters. These were made by companies like HP but are now obsolete. These crystals will have a fine frequency adjustment on them that was intended to be set by a technician using a laboratory calibration standard. Here is the key, Connect the oscillator output to an analog pin of a microcontroller, like an Arduino. The computer counts the cycles and with an analog pin, can measure phase. The computer also is connected to the 1Hz output of a GPS. GPS output is VERY good in the long term. It is very stable over months and years but each pulse might have up to 50 nanoseconds jitter (for more money you get 5ns jitter) The software measures the phase of the crystal and the GPS and makes very tiny adjustments to the crystal to keep it phase-locked to GPS. We can easily measure phase to 1,024 parts per cycle. After a few days, the system is locked. You might ask how I know I have 10 digits precision, don't ask. It means you need several better clocks and a way to cross-reference them. I bought a couple rubidium clocks as even these are now obsolete for cell tower frequency control, and you can buy them from Chinese companies that salvage old cell towers for $100 per unit. You slave there to a better GPS and then filter with a Cystal General Relativty predicts that tiime runs slower if gravity is stronger. The best clocks now can measure this effect if you move them from a desk to a tall shelf because gravity is weakers on the shelf then the desk. This is the curent state of the art for portible clocks that can be lifted by one person. Hint: We can locate objects from gravitational attraction's effect on time. Massive objects are getting harder to hide. because mass warps space-time. SO, we can do 13-digits on a high-end hobby budget -- government labs do better. > > Does anyone here know of some brands/ models to check out? > > > > Google has pointed me at some Acuity products but I wondered if there > > were other options besides that. > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > Cheers, Gene Heskett. > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > > > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
