accurate angle measurement

That is a bit little information. There can be optical masks with micrometer resolution. Is your problem a scientific problem to be solved once, a technical problem to be solved repeatedly or a business problem to be solved cheapest in numbers.

Rene

Wow.

Theodolites implies angle - more of less.

A rate gyro, on a chip?

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Joerg can make it cheaper :-)

martin

martin griffith a écrit :

But only Philips and Infineon make that dreadfully required component.

Rene, I want to measure the angle position of a 4~6 cm radius disc. Does it help? Thanks

Rene Tschaggelar ha escrito:

Avago (was Agilent (was HP)) make some quite nice absolute and incremental encoders (14 bit). ( If you have real money there are some laser based encoders that work down to a few arc seconds, and also some rotary transformer based solutions. )

You need to specify:-

Absolute or Incremental ?

Accuracy?

Angular speed and acceleration?

Do you require 360 degree revolution ?

How much do expect to spend ?

Dave

A little calculation shows that a pointer/scale one-arcsecond system on the disk requires alignment precision (and also axis-of-rotation position) of 0.14 microns. That's not possible with simple light-readout systems.

For reference, a CD squeezes about 6170 bits into one degree of disk rotation, with good diffraction-limited optics and lotsa tricks (like servo-controlled tracking mechanisms). That's 1.7 bits per arcsecond of rotation.

One can just about use lightbeam interferometry to measure a triangle's sides to this precision, but it's not gonna be a simple measurement.

Hi Dave,

My needings are: incremental, accuracy half second or second at most, speed 1.5 revs/sec at most, yes 360 degree, $ 500 to 700 approx Thanks

Dave ha escrito:

Add a 'k' to those values and you just might do it.

Do you really mean seconds ? To put what you've said in context, that's less than the width of a motorway measured from the centre of the earth.

- Steve

Another way: you're asking for 1 part in 1296000 _accuracy_. Even that kind of _resolution_ is not easy.

John Perry

Apparently you have never worked with any high resolution angle measurement systems. I can do that using 1950's technology, all gears and some tubes as needed. Back in the 1970 i saw 30 bit per revolution systems, i expect that better can be readily achieved today.

A rotary transformer based solution is the Inductosyn (Farrand Controls

To encode the Inductosyn position, you can get an Inductosyn to digital converter or design your own.

In a former life we did our own encoder. Using a 16 bit ADC, we encoded position to 18 bits per degree, or about 0.01 arc-seconds. Accuracy however was not better than the Inductosyn, which was about 0.5 - 1 arc-second for IIRC a 12 inch diameter model. Achieving this level of accuracy required the use of patented calibration techniques.

Marc