Accordingly to datasheet, but not exceed +5V. From the output of OA use a
small resistor and a 5V1 0.5W zenner.
Vasile

On Mon, 8 Oct 2001, MATTHEWS, DEAN (D.) wrote:

> All,
>
> I propose to use the onboard a/d converter to process a varying analogue signal.  I would like to protect the a/d converter from external voltages exceeding 5v.  Would it be best to use a 4.7v zener diode or a 5.1v zener.  What is the maximum voltage that the a/d converter will permit.
>
> Dean Matthews
> Reliability Engineering
> Ford Engine Plant Bridgend
> South Wales, U.K
> Tel No:(01656)672597
> Fax No:(01656)672558
> Email: dmatth14@ford.com
> ` Please consider your environmental responsibility before printing this e-mail
>
>
> -----Original Message-----
> From: Bob Ammerman [mailto:rammerman@ADELPHIA.NET]
> Sent: 27 September 2001 12:49
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: SCALING A/D CONVERTER
>
>
> Please don't shout!
>
> You can adjust the Vref+ of the PIC to improve your resolution somewhat, but
> not to a value as low as 1 volt. You will need an external opamp.
>
> Bob Ammerman
> RAm Systems
> (contract development of high performance, high function, low-level
> software)
>
>
> ----- Original Message -----
> From: "MATTHEWS, DEAN (D.)" <dmatth14@FORD.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Thursday, September 27, 2001 4:31 AM
> Subject: Re: [PIC]: SCALING A/D CONVERTER
>
>
> > I AM PROPOSING TO USE THE 40PIN 16F877.  I HOPE TO USE THE ONBOARD AD
> CONVERTER TO PROCESS A VARYING DC ANALOGUE SIGNAL RANGING BETWEEN 0 AND
> 1VOLT.  DOES THE PIC HAVE A FUNCTION THAT WOULD ENABLE ME TO SCALE THIS
> VOLTAGE OR DO I NEED AN EXTERNAL AMPLIFIER TO AMPLIFY THE SIGNAL TO ARROUND
> 4VOLTS TO GET BETTER RESOLUTION.
> >
> > Dean Matthews
> > Reliability Engineering
> > Ford Engine Plant Bridgend
> > South Wales, U.K
> > Tel No:(01656)672597
> > Fax No:(01656)672558
> > Email: dmatth14@ford.com
> > ` Please consider your environmental responsibility before printing this
> e-mail
> >
> > --
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> >
> >
>
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