Unless you aren't planning on submerging your probe more than 100 feet, you
may want to rethink the RS-232. Maybe 422 or some other differential
solution would prove more robust. I think the '71 is a good choice if you
need compact size and performance.

Tom

On Monday, March 02, 1998 7:48 AM, Wayne Foletta
[SMTP:foletta@IX.NETCOM.COM] wrote:
> James - You wrote:
> >
> >Hi Wayne,
> >        How would I obtain this information ? Manufacturer or trial and
> >error ?
> If the manufacturer does not publish a "Percent Change of Light Output vs
Time"
>  you
> could estimate it for the generic type (GaAs is better than GaAlAs) and
use
>  other
> manufacturer's specs. Otherwise test aging yourself with a linear
photodector.
>  Also
> remember temperature is major factor in LED light output (-0.5% per
degree
>  typical).
>
> >As far as time goes, the counters would only be underwater for 12 to
> >18 hours at
> >the most. But a concern would be that the display stopped working
> >while down below.
> >If a return trip had to be made because the display was out it could
> >get very costly in a hurry
> >at multiple thousands of dollars per hour.
> >        I just returned from looking at your web page.. I would sure
like to
> >pick your brain about
> >the next project. A 2 axis inclinometer that will send RS232 up to
> >the surface. I was thinking of
> >using the PIC 12C671 with it's built in A/D converters and 2 pins
> >left for RS232.
> >        Thanks for taking the time to reply to my post.
> >        James Holbrook
> >
> >On Saturday, February 28, 1998 8:21 AM, Wayne Foletta
> >[SMTP:foletta@IX.NETCOM.COM] wrote:
> >> Be sure to check the "half-life" spec of the LEDs versus forward
> >> current for the LEDs you are using. With some brands of LEDs the
> >> light output falls off very quickly at higher currents (over 20%
> >per
> >> decade of time at 2X rated maximum If).
> >>
> >> Wayne Foletta
> >> Data Acquisition Engineering
> >> SiliconSoft, Inc.
> >> http://www.siliconsoft.com
> >
>