Re: [CAD_CAM_EDM_DRO] Re: sine wave encoder outputs

Hi Mariss,

I'd be very interested to see the circuit.

Thanks,
Lee


At 06:23 PM 9/24/00 -0000, you wrote:

>
>Hi, The main advantage of a sine/cosine encoder is the absence of
>servo "dithering" when stopped. Unless it is an extremely accurate
>(read expensive) encoder, any scheme to increase resolution is
>unsatisfactory for the following reasons:
>
>1) Encoders have a cyclic amplitude modulation; a sine/cosine
>amplitude of +/- 1 volt may be +/- 1.2 volts when the encoder is
>turned 180 degrees.
>
>2) Any resolution enhancing scheme depends on a 90 degrees
>relationship between the two channels. This cannot be gauranteed.
>
>3) The waveform more than likely is a "quasi-sinewave". This means it
>actual waveform will be somewhere between a sinewave and a triangle
>wave.
>
>4) Even if the encoder is perfect, the circuitry necessary to extract
>additional resolution is complex and expensive.
>
>Apart from the "non-dithering" advantage, the expense of
>interpolation is better spent on a higher resolution digital encoder.
>If anyone is interested, I can post a circuit I designed that
>extracts an analog voltage proportional to position between encoder
>counts.
>
>Mariss
>
>--- In CAD_CAM_EDM_DRO@egroups.com, "Elliot Burke" <elliot@h...>
>wrote:
>> Does anyone know a way to convert (4 phase)sine wave encoder output
>to allow
>> interpolation of the phases?
>> It should be possible to greatly multiply the pulse resolution by
>> interpolation. The encoder has a spec of 10° precision of the
>quadrature
>> phases, so that limits accuracy for large interpolations.
>>
>> Elliot Burke
>
>
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