From: yaniv_vi_at_yahoo.com
Date: 2001-05-21 12:23:39
hi
if we want to use some kind of opto couplers it's o.k. , but i would
prefer dicrete , and the transiter of the opto coupler is in one
plastic box , and the reciever is in another .
the boxes preferably have like 10 cm of distance , and if not another
way of making sure that now way a safety breach would ocur .
this could maybe save some design complexiti and time bute still give
perfecty safety .
but i don't feel that we should settle for more then total safety .
and i have understood that input stage design is done .
cheers !!!! (it was you jeorg ? very nice .i haven't got time
to look on eagle now - very busy in traveling just returned from
reking - sorry , but if you designed it's cool !!!)
sincerly
yaniv
--- In buildcheapeeg_at_yahoogroups.com, "Joerg Hansmann" <info_at_jhansmann.de> wrote:
> Hi,
>
> ----- Original Message -----
> From: JBilderback <jiva_at_humboldt1.com>
> To: <buildcheapeeg_at_yahoogroups.com>
> Sent: Thursday, May 17, 2001 4:39 PM
> Subject: [buildcheapeeg] optocoupler isolation
>
>
> > >
> > > The other option would be to use the RS232 port and some
optocouplers.
> > > Does anybody know what isolaton voltage is common in eeg
equipment ?
> > > I think the brainmaster has about 160V which sounds quite low
to me.
> > > Does anybody know types of optocouplers normally used in
medical equipment ?
> > > Another idea is to built an optocoupler by ourselves using
phototransistors and
> > > IR LEDs. That would probably also result in a very high
isolation voltage.
> > >
> >
> > the til111 used in Bernd Porr's preamp design posted by john
anand specs
> > at 1500v.
> >
> > http://www.isocomoptocouplers.com/isocom/til111.htm
>
>
> 1500V is _not_ sufficient if we want a IEC601-1 certification.
>
> 3750Vrms or 5300Vpeak (or better 5500Vpeak) (@50/60Hz) seems to be
the
> standard for EEGs.
> e.g.:
>
> www.sensoriuminc.com/manual.pdf
> "EPA-6 Electro-Physiology
> Amplifier
> Reference Manual
> ...
> Isolation: 3750 Vrms, 60Hz,continuous
> ...
> The low pass filter stage is followed by
> an isolation amplifier. The isolation element
> consists of a LED emitter coupled through a
> servo circuit with a photodiode. A second
> photodiode detects the amplitude of light.
> Optical isolation..."
>
> In this professional device the isolation is done with
> discrete IR-emitters and photodiodes. The reason
> for using a discrete solution is probably, that
> integrated optoisolators for the required voltage
> are not available.
>
>
> Regards,
>
> Joerg
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:30 BST