Dr David Kirkby Ph.D C.Eng MIET Email: [email protected] Web: https://www.kirkbymicrowave.co.uk/ Kirkby Microwave Ltd (Tel 01621-680100 / +44 1621-680100) Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3 6DT.
On Sun, 28 Jun 2020 at 12:44, Tom Van Baak <[email protected]> wrote: > About slabs and stability... Around the world there must be a hundred > precision time labs, including official NMI (National Metrology > Institute) labs that contribute to the calculation of UTC itself. You > run into photos of these labs and their T&F gear on the web all the time > when you search for time nutty stuff. Those of us with home labs -- even > if just a few vintage frequency standards -- can relate. > > Anyone, one of my favorite lab photos is from VSL, the Dutch Metrology > Institute. Photo attached. [1] > > Spend time time pan/zooming around the gear in the photo. The usual > suspects: hp 105 quartz; TimeTech (I think); lots of SDI > (Spectradynamics); also Truetime or Symmetricom stuff; maybe that's an > old Tracor/Fluke VLF receiver on the far right (?); and of course lots > of Stanford Research SR620 counters, the TIC still used by almost every > time lab. > > But what really caught my eye was not just the four hp 5071A in the > foreground but *how they are mounted* -- on top of massive granite blocks! > There's a picture of a granite block here, at a former place I used to work as a student - EQD Aquila, the MODs calibration labs. https://www.derelictplaces.co.uk/main/military-sites/14101-aquila-mod-testing-facility-bromley-march-2004-a.html#.XvirQuco9PY about 60% of the way down the page. (Some of the pictures are quite amusing, as well as some of scientific interest). There's a couple of guys at my radio club used to work somewhere where a milling machine was turning high precision device. I just phoned one to ask what they used for anti-vibration, as I knew they took some precautions. He said they had dug a hole about 2 m into the ground, above that was 600 mm of "rubber", then 1.4 m of reinforced concrete. That used to stop lorries messing up the work. That's a different sort of application. I assume the OPs objects are quite large - not wrist watches. Otherwise, I was wondering if an active damping system might be practical. They certainly exist for laser tables https://www.newport.com/n/active-vibration-damping but I would imagine that for heavy 19" rack equipment, there would need to be quite a bit of power consumed in such a system. I've never done any calculations - just intuitively, I can't imagine that one could achieve anything useful without some pretty big power amplifiers. When I worked at UCL we had a laser table. Our department was near a main road. The laser table had gas-filled "dampers", but apparently these made the vibration problems worse rather than better, so the gas was removed. We never had any active system. Dave _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
