NS Dev
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| posted on 1/11/05 at 09:04 AM |
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Digital Vernier Calipers, how do they work?
Anybody know what the innards of a digital vernier are and how they work.
I'm kinda hoping that somebody will say they use an LVDT, which would mean I can use the innards from a pair of them on a rig at work.
I guess they are not potentiometers as these would not be very robust but can anybody shed any light on this for me?
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flak monkey
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| posted on 1/11/05 at 09:33 AM |
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AFAIK they have a digital encoder in them. What type, I am not sure.
It is probably a linear encoder that counts pulses as the jaws are moved. Fully digital.
Its unlikely to be based on an LVDT as they are bulky and very very expensive if you require one with a stroke of 150mm and a resolution of
10mircometers.
I of course could be wrong.
David
Sera
http://www.motosera.com
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NS Dev
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| posted on 1/11/05 at 11:04 AM |
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Cheers Flak!
Put me on the right track and I now know!
They use one of two systems, the most common being capacitive position sensing linear encoder, basically a segmental variable capacitor but made very
accurately.
I have now also learnt that touch sensitive monitor screens and laptop touchpads use the same device.
REALLY clever stuff that I have never heard of. The laptop pad is a grid of electrodes embedded in epoxy which uses the capacitance of one's
finger to give coupling between the pads when they are driven at a given frequency. the pads are scanned very rapidy with the frequency in a similar
fashion to tv display and the variation in coupling from pad to pad gives a map of movement direction and speed very accurately!!! really
clever!!
Touch screen is the same but with clear electrodes!
Vernier is the same, much simpler but very accurately made, and uses a capacitance built into the moving part instead of a human finger!
Those touch sensitive dimming lamps apparently use the capacitance of the human body when driven at mains electricity frequency (50hz) to operate the
on off and dimmer!
I have really learn't something today!!
Cool!
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tobymack
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| posted on 2/11/05 at 09:38 AM |
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you might already of seen this but this patent by mitutoyo gives a lot of detail....
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&am
p;u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=4,879,508.WKU.&OS=PN/4,879,508&RS=PN/4,879,508
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