Re: Condensation and off by one byte again...

[Tom Droege <tdroege2@earthlink.net>]

Rob,

I am replying to the group since I think this is of general interest.

It is possible for the "one off" problem to happen any time.  It happens to 
me possibly every couple of months.  It should restore on the next image.

The reason is that a noise spike can strobe an extra byte into the memory 
card.  It is just a question of a large enough noise spike.

To reduce the possibility of this happening:

1) Keep the cable between the computer and the camera short.
2) Use a shielded output cable between the Mark IV and the computer.
3) Don't use a shielded output cable between the Mark IV and the computer.
4) Plug the computer into the same outlet as the Mark IV.
5) Make the path that the output cable takes to get to the computer the 
same as the path that the power cord for the Mark IV takes to get to the 
computer.

You may notice a minor conflict between rule 2) and 3).  You try 
both.  Most likely 2) will be the best.  But this is black magic.  3) might 
be better.  To guess which one, you have to really understand the whole 
noise picture.  If you think you have a noise problem, then I will work 
with you to solve it.  I have done this for many years.  You may need to 
really understand where the signals go and where noise comes from in your 
location.

Rob, I think you have your computer in the same box with the Mark IV.  So 
mostly worry about how you get power there.  An outlet strip in the "dome" 
with both the Mark IV and the Computer plugged into it should work OK.  The 
all you should have back to the garage is an ethernet cable and a power 
cord.  Just make sure they follow the same path.  You might twist them 
together if you are paranoid.

Below, I think you mean one pair was good and the next pair bad.  How about 
the pair after the bad pair?  If it is OK, then you just have a noise 
problem.  If it stayed bad for many frame pairs, then I would work on the 
reset.

Heh! Heh!  Mark IVs are not so free.  They are an excuse to buy the latest 
and greatest computer, I think.

Tom



At 10:44 AM 3/13/03 -0700, you wrote:

>Hey Tom,
>
>Looking at my images, it appears that the condensation is clearing during 
>the night run, and showing up during the day.  Oh well.  I'm gunna try to 
>find a spanner wrench for the future, and heating tape for the present.
>
>During my run last night, the one byte off problem showed up, between two 
>picture sets.  One image set was fine, the next off by one byte.  Could a 
>reset sequence which occurs too fast cause this?  I have not yet put in 
>any delays to see what happens.  Other ideas?
>
>I'm about to order one of those dual AMD systems, as my current machines 
>take a few days to reduce one night's worth of data...
>
>Cheers,
>Rob
>
>Robert Creager
>Senior Embedded Software Engineer
>ATS Library Engineering
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