I took a look inside the shaft encoder attached to a DC servo motor
and was rather expecting to see a standard A/B quadrature optical
assembly with a glass wheel, an LED illuminator and the usual optical
pickup assembly.

Whet is ended up with is http://www.idesignz.org/misc/shaft_enc.jpg
which looks a bit more like a tape head mounted close to a roller
wheel.

The head appears to be thin film, and I assume that the wheel is some
form of electromagnetic assembly - possibly like a resolver. There is
a small air gap separating the two.

Any idea what the name of this technology is and who might be
manufacturing it ?

Thanks,

Mark

"MarkAren" <m...@yahoo.com> wrote in message 
news:a...@s33g2000prm.googlegroups.com...
>I took a look inside the shaft encoder attached to a DC servo motor
> and was rather expecting to see a standard A/B quadrature optical
> assembly with a glass wheel, an LED illuminator and the usual optical
> pickup assembly.
>
> Whet is ended up with is http://www.idesignz.org/misc/shaft_enc.jpg
> which looks a bit more like a tape head mounted close to a roller
> wheel.
>
> The head appears to be thin film, and I assume that the wheel is some
> form of electromagnetic assembly - possibly like a resolver. There is
> a small air gap separating the two.
>
> Any idea what the name of this technology is and who might be
> manufacturing it ?
>
> Thanks,
>
> Mark


No idea who made that one but the technique is pretty common. I've seen it 
used in wind measurement instruments and IIRC the other one was in some 
domestic application with a magnetoresistive sensor. The wind measurement 
was single channel only for speed, ie not quadarature.

Looks like quite a few conductors going to the sense head. 

Royston Vasey wrote:
> 
> "MarkAren" <m...@yahoo.com> wrote in message
> news:a...@s33g2000prm.googlegroups.com...
> >I took a look inside the shaft encoder attached to a DC servo motor
> > and was rather expecting to see a standard A/B quadrature optical
> > assembly with a glass wheel, an LED illuminator and the usual optical
> > pickup assembly.
> >
> > Whet is ended up with is http://www.idesignz.org/misc/shaft_enc.jpg
> > which looks a bit more like a tape head mounted close to a roller
> > wheel.
> >
> > The head appears to be thin film, and I assume that the wheel is some
> > form of electromagnetic assembly - possibly like a resolver. There is
> > a small air gap separating the two.
> >
> > Any idea what the name of this technology is and who might be
> > manufacturing it ?
> >
> > Thanks,
> >
> > Mark
> 
> No idea who made that one but the technique is pretty common. I've seen it
> used in wind measurement instruments and IIRC the other one was in some
> domestic application with a magnetoresistive sensor. The wind measurement
> was single channel only for speed, ie not quadarature.
> 
> Looks like quite a few conductors going to the sense head.

The wheel may have several 'tracks' to give better angular resolution.

-- 
Paul Hovnanian     mailto:P...@Hovnanian.com
------------------------------------------------------------------
Rube Goldberg is alive and working for Microsoft.

On Wed, 17 Feb 2010 06:41:19 -0700, Paul Hovnanian P.E. wrote:

> Royston Vasey wrote:
>> 
>> "MarkAren" <m...@yahoo.com> wrote in message
>> news:a...@s33g2000prm.googlegroups.com...
>> >I took a look inside the shaft encoder attached to a DC servo motor
>> > and was rather expecting to see a standard A/B quadrature optical
>> > assembly with a glass wheel, an LED illuminator and the usual optical
>> > pickup assembly.
>> >
>> > Whet is ended up with is http://www.idesignz.org/misc/shaft_enc.jpg
>> > which looks a bit more like a tape head mounted close to a roller
>> > wheel.
>> >
>> > The head appears to be thin film, and I assume that the wheel is some
>> > form of electromagnetic assembly - possibly like a resolver. There is
>> > a small air gap separating the two.
>> >
>> > Any idea what the name of this technology is and who might be
>> > manufacturing it ?
>> >
>> > Thanks,
>> >
>> > Mark
>> 
>> No idea who made that one but the technique is pretty common. I've seen it
>> used in wind measurement instruments and IIRC the other one was in some
>> domestic application with a magnetoresistive sensor. The wind measurement
>> was single channel only for speed, ie not quadarature.
>> 
>> Looks like quite a few conductors going to the sense head.
> 
> The wheel may have several 'tracks' to give better angular resolution.

Usually a fairly broad track, covered by two reading heads, displaced to
give quadrature between. It's easier to make than trying to lay down two
quadrature tracks.

Probably also a one-pulse per rev "index Z" track, usually a raised cosine
pulse shape.

Magnetic encoders are usually high resolution, so there are possibly more
than one set of quadrature signals at differing PPR.

-- 
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
                                             (Stephen Leacock)

MarkAren wrote:
> I took a look inside the shaft encoder attached to a DC servo motor
> and was rather expecting to see a standard A/B quadrature optical
> assembly with a glass wheel, an LED illuminator and the usual optical
> pickup assembly.
> 
> Whet is ended up with is http://www.idesignz.org/misc/shaft_enc.jpg
> which looks a bit more like a tape head mounted close to a roller
> wheel.
> 
> The head appears to be thin film, and I assume that the wheel is some
> form of electromagnetic assembly - possibly like a resolver. There is
> a small air gap separating the two.
> 
> Any idea what the name of this technology is and who might be
> manufacturing it ?
> 
> Thanks,
> 
> Mark

Googling for "magnetic shaft encoder" finds many, eg:
http://www.gurley.com/Encoders/rotabs.htm


-- 
Regards,

Adrian Jansen           adrianjansen at internode dot on dot net
Note reply address is invalid, convert address above to machine form.

"Fred Abse" <e...@invalid.invalid> wrote in message 
news:p...@invalid.invalid...
> On Wed, 17 Feb 2010 06:41:19 -0700, Paul Hovnanian P.E. wrote:
>
>> Royston Vasey wrote:
>>>
>>> "MarkAren" <m...@yahoo.com> wrote in message
>>> news:a...@s33g2000prm.googlegroups.com...
>>> >I took a look inside the shaft encoder attached to a DC servo motor
>>> > and was rather expecting to see a standard A/B quadrature optical
>>> > assembly with a glass wheel, an LED illuminator and the usual optical
>>> > pickup assembly.
>>> >
>>> > Whet is ended up with is http://www.idesignz.org/misc/shaft_enc.jpg
>>> > which looks a bit more like a tape head mounted close to a roller
>>> > wheel.
>>> >
>>> > The head appears to be thin film, and I assume that the wheel is some
>>> > form of electromagnetic assembly - possibly like a resolver. There is
>>> > a small air gap separating the two.
>>> >
>>> > Any idea what the name of this technology is and who might be
>>> > manufacturing it ?
>>> >
>>> > Thanks,
>>> >
>>> > Mark
>>>
>>> No idea who made that one but the technique is pretty common. I've seen 
>>> it
>>> used in wind measurement instruments and IIRC the other one was in some
>>> domestic application with a magnetoresistive sensor. The wind 
>>> measurement
>>> was single channel only for speed, ie not quadarature.
>>>
>>> Looks like quite a few conductors going to the sense head.
>>
>> The wheel may have several 'tracks' to give better angular resolution.
>
> Usually a fairly broad track, covered by two reading heads, displaced to
> give quadrature between. It's easier to make than trying to lay down two
> quadrature tracks.
>
> Probably also a one-pulse per rev "index Z" track, usually a raised cosine
> pulse shape.
>
> Magnetic encoders are usually high resolution, so there are possibly more
> than one set of quadrature signals at differing PPR.
>
> -- 
> "Electricity is of two kinds, positive and negative. The difference
> is, I presume, that one comes a little more expensive, but is more
> durable; the other is a cheaper thing, but the moths get into it."
>                                             (Stephen Leacock)



These guys have some cool mag encoder ICs. I've got a sample kit I must play 
with one day....

http://www.austriamicrosystems.com/eng/Products/Magnetic-Encoders

On Thu, 18 Feb 2010 08:34:01 +1000, Adrian Jansen <a...@qq.vv.net> =
wrote:

>
>MarkAren wrote:
>> I took a look inside the shaft encoder attached to a DC servo motor
>> and was rather expecting to see a standard A/B quadrature optical
>> assembly with a glass wheel, an LED illuminator and the usual optical
>> pickup assembly.
>>=20
>> Whet is ended up with is http://www.idesignz.org/misc/shaft_enc.jpg
>> which looks a bit more like a tape head mounted close to a roller
>> wheel.
>>=20
>> The head appears to be thin film, and I assume that the wheel is some
>> form of electromagnetic assembly - possibly like a resolver. There is
>> a small air gap separating the two.
>>=20
>> Any idea what the name of this technology is and who might be
>> manufacturing it ?
>>=20
>> Thanks,
>>=20
>> Mark
>
>Googling for "magnetic shaft encoder" finds many, eg:
>http://www.gurley.com/Encoders/rotabs.htm

Helpful at least.  Looking at the photo i believe it is an at least 8 bit=
=20
absolute position encoder.  Many of these thing use Gray code.

http://en.wikipedia.org/wiki/Gray_code