This is mine, used to calibrate some aircraft related equipment: https://www.flickr.com/photos/103726899@N08/33326340242/in/dateposted-public/
and its diagram: https://www.flickr.com/photos/103726899@N08/33482556075/in/dateposted-public/ iov >----Messaggio originale---- >Da: "Mike Seguin" <n1...@burlingtontelecom.net> >Data: 16/03/2017 22.33 >A: "Discussion of precise time and frequency measurement"<time-nuts@febo.com> >Ogg: Re: [time-nuts] Antique precision timing device without electronics > >Very interesting use of a tuning fork. > >I have only seen this once before. I have the tuning fork used with an >Ampex Model 300 reel to reel tape machine. The tuning fork was used as a >reference in the power supply that drove the capstan motor for accurate >speed. > >It's 60 Hz not 25 Hz. It's marked B E Eisenhour. Patent is here: > >https://www.google.com/patents/US1880923 > >Pic is here: > >https://www.dropbox.com/s/opmxr521qqkx76r/60%20Hz%20Fork.jpg?dl=0 > >Mike > >On 3/16/2017 2:04 PM, Bill Hawkins wrote: >> Hi Morris, >> >> If there's no active devices (and you'd be sure to see them, not solid >> state) where does the power to operate the motor come from? Is it the >> same contacts that drive the fork? >> >> It's amazing that there is high Q when contacts must be operated by the >> fork. >> >> Did it come with instructions for setting the weights at the end of the >> fork tines? >> >> Best regards, >> Bill Hawkins >> >> -----Original Message----- >> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Morris >> Odell >> Sent: Thursday, March 16, 2017 4:23 AM >> To: time-nuts@febo.com >> Subject: [time-nuts] Antique precision timing device without electronics >> >> Hi all, >> >> I was recently asked to resurrect this interesting device by a colleague >> who collects antique scientific instruments. It's a "Chronoscope" made >> by the H. Tinsley company in London in the early 20th century and used >> to measure time intervals with the precision of those days. It's large >> and heavy in a polished wooden case with a top deck that hinges up to >> reveal the innards. >> >> The timing reference is a large tuning fork about 30 cm (1 foot) long >> and running at 25 cps. It's normally in a glass fronted housing (removed >> for the video) that includes a pair of hinged mechanical arms for >> starting it. It's maintained in oscillation by an electromagnet and >> contact arrangement powered from a 12V DC supply. The fork amplitude is >> controlled by a rheostat - too much and the tines impact on the magnet. >> The video frame rate makes the fork look slower than it actually is. I >> was able to extract a signal and measure the frequency with a modern GPS >> disciplined counter - it's 0.007% off its specified 25 Hz! The frequency >> is too low for my HP 5372A so I was not able to easily get an idea of >> stability or do an ADEV measurement. The fork has quite a high Q and >> takes over a minute to stop oscillating after the power is turned off. >> There's a built in higher voltage AC power supply, probably a mains >> transformer, potted in beeswax in a polished wooden box inside that is >> intended to >> energise a large neon strobe lamp used to adjust the fork. >> Unfortunately the lamp was not with the unit and is no doubt >> irreplaceable. >> >> The 25 Hz signal is filtered by an LC network and used to run a >> synchronous motor in the Chronoscope unit. Synchronous motors not being >> self-starting, you need to tweak a knob to get it going - there's a joke >> in there but I can't for the life of me think what it could be ?? The >> "Contact" switch and associated socket on the back controls an >> electromagnetic clutch that connects the clockwork counter mechanism to >> the motor and the contact "on" time is indicated on the dials with 10 mS >> resolution. >> >> There's not a single active device in there and after a clean and lube >> it runs very nicely from a modern 12V DC plugpack. My friend is very >> pleased with it and it will take pride of place in his collection. >> >> I'd be interested to know if any time nuts have knowledge or experience >> of this lovely instrument. >> >> A video of it is at https://youtu.be/i5S8WS9iN_E >> >> Enjoy! >> >> Morris >> >> _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.