Re: Proximity sensor for RSG

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <classictesla-at-netzero-dot-com>

Marco,

Inductive sensors are not magnetic sensors. Inductive sensors will detect 
any metal.

Take care,
Bart

Tesla list wrote:

>Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><Marco.Denicolai-at-tellabs-dot-com>
>
>Hello all,
>
>I eventually purchased an inductive proximity sensor which is intended
>for use with welding robots. Its front face is teflon covered and can
>stand static and pulsing magnetic fields up to 200 mT.
>
>I'll get it within two weeks. Let's see if it will detect the metal
>mixture of Thor's electrodes (tungsten 1.5 mm and steel). I found
>nowhere the reduction factor for 2% thoriated tungsten.
>
>Anybody any clue about 2% thoriated tungsten magnetic properties (the
>dope is actually thorium dioxide, IMHO)?
>
>Regards
>
> > -----Original Message-----
> > From: tesla-at-pupman-dot-com [mailto:tesla-at-pupman-dot-com]
> > Sent: 20. maaliskuuta 2003 23:08
> > To: tesla-at-pupman-dot-com
> > Subject: Re: Proximity sensor for RSG
> >
> >
> > Original poster: "Jim Lux by way of Terry Fritz
> > <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>
> >
> > I think your real problem is going to be finding a sensor that is EMI
> > immune. The magnetic sensors (hall effect) are fairly low
> > level signals (at
> > least internally).
> > I'd think some sort of optical pickup is your best bet.  If
> > you've got a
> > bit of optics (i.e. some small convex lenses) you could make
> > something that
> > can be a bit of distance from the rotor, and furthermore,
> > which can keep
> > all the electronics in a shielded box.   A laser diode makes
> > a nice bright
> > source that's visible, for alignment. A red filter over the
> > detector helps
> > improve the SNR, and you can just use any old photodiode or
> > transistor as a
> > detector, and capacitively couple the output.  To restrict
> > the field of
> > view, you can either use a lens, or just put the detector at
> > the end of a
> > tube that's painted black on the inside, so it can't "see"
> > anything except
> > the target spot.
> >
> > If you really want to get the SNR up, make your targets out of that
> > retroreflective tape (ScotchBrite reflector...)
> >
> > At 11:32 AM 3/20/2003 -0700, you wrote:
> > >Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>"
> > ><Marco.Denicolai-at-tellabs-dot-com>
> > >
> > >Hello all,
> > >
> > >I would like to add to Thor's rotating spark gap a position sensor to
> > >know when the rotating electrodes face the fixed ones. I
> > don't need to
> > >know the absolute position (degrees), just an digital signal
> > is enough.
> > >I'll use that to synchronize the primary capacitor charge
> > and to count
> > >the bang amount.
> > >
> > >The RSG features a 30 cm diameter rotor, with 12 rotating
> > electrodes (2%
> > >thorium doped tungsten, 0.5" in diameter). The motor is a 2850 rpm,
> > >achieving a maximum bang-rate of 570 breaks/s. I calculated:
> > >
> > >- min. face time = 1.27/(PI*30*2850/60) = 0.28 ms
> > >- min. period = 1/570 = 1.75 ms
> > >
> > >I was thinking to detect the rotating electrode proximity or painted
> > >black spots on the rotor side. I don't want to drill holes
> > or whatever
> > >to the rotor.
> > >
> > >I need help in choosing the right proximity sensor: capacitive,
> > >inductive or magnetic? What will work? Anybody with
> > experience on this?
> > >
> > >Regards
> >
> >
> >
> >
>
>
>
>