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Comment by T3OU-736 | Hacker News Reader

Watching this, a couple of questions came up in my mjnd:

1. Siemens rep physically touching things despite vibration sensors being in place - do they not trust the sensors? If they do not, how are they doing routine monitoring? Have someone sit atop the machine and feel for things 24/7? Or is that just the rep grandstanding for the cameras?

2. Time of grid sync only having hh:mm precision. Nitpick, but at 60hz, that is about 50s of imprecision.

3. The mentioned previous unsuccessful attempts - so went wrong? Dunno, I tend to learn more about systems from failure :)

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> Siemens rep physically touching things despite vibration sensors being in place - do they not trust the sensors? If they do not, how are they doing routine monitoring? Have someone sit atop the machine and feel for things 24/7? Or is that just the rep grandstanding for the cameras?

You ever give a pair of kitchen tongs a few good clacks before using them? You know, just to make sure they're still clacking?

The building I currently work in used to have clocks that were synchronized by the power grid. The power company would guarantee a number of cycles per day. While the precision isn't always there your clocks would never be permanently drifted and that was good enough.

I haven't looked into it but the guy who sold me our current gps time receiver told me that power companies no longer offer a cycle guarantee.

A friend of mine lived in a deliberate-built uranium mining town about 30 km away from the Trans-Canada Highway. One day, it disconnected from the main grid for one reason or another, but still had power from a local hydroelectric dam.

The dam ran too slow, and everyone who relied on wired clocks ended up being 15 minutes behind in their day.

In the European grid, grid time is tracked and adjusted as needed by nudging target frequency.

https://www.swissgrid.ch/en/home/operation/grid-data/current...

Thirty years ago I had a graduate assistantship in the physical plant of my university. One of the cool things I saw was a 55-gallon drum sized motor spin up to synchronize all the clocks on campus at noon.

It costs nothing to check. Gauges are one thing, but physical senses are good for intuition. It's no different from a racecar driver knowing their engine is underperforming because it sounds different.

If it's the first time the equipment has spun up after the sensors were installed, maybe he's just validating the installation. Maybe they wouldn't be doing that 24/7, just every month or year, the same way I don't validate unit tests constantly, only when I write them and then occasionally after.

> Siemens rep physically touching things despite vibration sensors being in place - do they not trust the sensors?

Trust but verify?

> Siemens rep physically touching things despite vibration sensors being in place

If the rep’s touch is calibrated, then it would perturb the sensors by a known amount and should validate the sensors are not resulting a metric that is permanently wrong.

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