On 11/19/18 1:41 PM, Al Kozakiewicz wrote:
The defeat of the Nazi's assisted by this analog technology has almost passed
completely from living memory. Rotary encoders are a fraction of the price and
already signal compatible with digital systems.
Or maybe I am missing something?
Al
Synchros (and these days, resolvers) are still widely used as sensors -
they're really rugged, inherently a balanced ratiometric device, so wire
length isn't a big deal, and its all twisted pairs (or triples) so noise
pickup is less of an issue. They laugh at ESD or transients - it's a
transformer - unless the discharge is big enough to destroy the winding,
it still works - you can punch holes in the insulation with HV
transients all day. They are also inherently dust/moisture/liquid
insensitive - the accuracy is more about the quality of the shaft
bearings and how precisely they can locate the rotor within the stator
windings.
You can easily transformer isolate them for galvanic isolation (a real
issue with long sensor wire runs - galvanic isolation is good)
Unlike a quadrature encoder, they're an absolute position sensor - no
need to "find home" and count pulses. Yes, there are absolute rotary
encoders, but they don't have 16 bit accuracy, without a geared scheme
and two encoders. 16bit accuracy is achievable off the shelf with a
resolver at moderate cost (a few kilobucks, brand new, for resolver+chip
to turn it into a digital number).
You'll also see the linear equivalent called a LVDT (Linear Variable
Differential Transformer)- same basic idea, a transformer made with a
stator with multiple windings, and a slider that has an excitation
winding. Used in the same sort of hostile industrial environments. You
don't need three phases (or quadrature) for an LVDT, because the motion
is constrained - no need for "unwrapping"
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