Hi Grant, that was me, and I think Jim Lux. Many thanks for the link.
Martin, HS0ZED
On 07/12/2018 05:05, Grant Saviers wrote:
Not sure who was looking for the voltage/current equations for
synchros but some data is in MIT Rad Lab Vol 25 Chapter 3. Found by
accident.
https://www.jlab.org/ir/MITSeries/V25.PDF
Grant KZ1W
On 11/19/2018 15:28 PM, jimlux wrote:
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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