synchros

Resolvers are a lot less common than synchros. There seems to be a pretty active market for Harosyn higher-frequency resolvers for some CNC application. They go for something like $220 used and $1800 new.

I really need 400 Hz stuff.

A pair of good quality permanent magnet DC servo motors will do that too. There will be some slip, of course.

Jeroen Belleman

steper motors.

OK, we can add synchros and resolvers to the very, very long list of things that you have no interest in.

Certainly NOT synchros or resolvers!

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John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com

Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

My synchros require 120 V 60 Hz to be supplied to each one. The other wires are connected together and the sybchro's shafts "follow" each other.

I remember three wires (keep in mind that I'm remembering back some 55 years :-) And they "angle followed". ...Jim Thompson

Two wire or more? Two wire would be permanent magnet motors for large computer tae drives.

There are such things as inverters for aircraft applications so the output will be clean:

Dunno how much, maybe $100 .

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Here's another way to get precision angle output:

This was when I was with Telecomputing. I don't know if anyone is still making this type of encoder.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Many years ago used to use selsyn (resolvers) in radar. Transmitter connected to the radar head turning gear so was locked to the rotation position/rate. Located remotely in the ops/display room was the receiver selsyn (a 3 wire link if I remember). Connected to the receive selsyn shafts were sine cosine pots which were injected with a sawtooth. Out of the pots you got phase and quad sawtooth which drove the PPI (plan position indicator) displays - the sine /cos sawtooth applied to the x & y deflection coils produce a rotating line vector anchored to the display centre. Radar video super imposed on the z mod gave the familiar 2d radar display.

Andy

Yup, that's what the ones I got were, and the market I am mostly working in. They are generally designed for 2500 Hz, but work fine at 10 KHz, which is the design frequency of the AD2S1200 chip. I run them at pretty low excitation to satisfy the chip's requirement of an output of 3.6 V P-P at the angle of maximum signal on the sin/cos outputs. In servo measurements, actually, resolvers are pretty common, used in a lot of machine tool gear. it gives you sin/cos voltages without the need for a Scott-T transformer set. Anywhere you would be using an amplifier to drive a servo to null, it is simpler. The old way was you had two selsyns, one on the thing to be measured, and one on the indicator. You excite the rotor on the source selsyn and observe the rotor output on the indicator selsyn, and that can be amplified and applied directly to one winding of a 2-phase induction motor, the other winding excited by a 90 degree phase-shifted excitation, and the motor will spin until the two selsyns are aligned. That is a mechaincal nightmare, but made sense in 1960.

Jon

Jon

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Cool, sort of a capacitive inductosyn. With toobs!

Air caps are interesting. It shouldn't be hard to measure nanometers with some flat metal blocks and a little electronics.

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Back in 1960, I worked on a transducer which measured very large, very short pressure impulses from within explosive devices. It used a small capacitive variation to tune an RF circuit, whose frequency change was used for the output.

The problem was temperature compensating the thing! It worked perfectly, but had to be "tuned" just before the measurement.

The problem with digital systems is that somewhere there has to be an "analog" component!

Andy, You rang the right chime... "selsyn" was the name my mind couldn't quite pull back up from "archives"

be clean:

Nice, but it's $525.

I'll go with a function generator, audio amp, and a transformer for now. That lets me futz frequency and voltage too.

Selsyns (archaic term for torque synchros) wouldn't work without power.