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Re: Dry Cameras



The main use of this discussion is to keep my mind occupied until the sky
clears so I can test the modified system.

Tom Croege

At 10:59 AM 5/12/00 -0500, you wrote:
>
>tom
>
>you are getting close . .  but since yours is based upon lee's suggestion
>the monies would have to be split between the two of you
>
>but, i have not put a time limit so we will wait and see :]]]
>
>jamie
>
>
>On Fri, 12 May 2000, Tom Droege wrote:
>
>> Hmmm!  I could hang the paper up on the wall, and have both cameras look at
>> it.  Since there are two different filters, I could calibrate the result
>> and figure out what color it is to match the table below.  Of course we
>> could do no useful work with the camera system, just measure the relative
>> humidity.  But that is OK, as the real objective of this project is to win
>> jamie bush's $5 Rube Goldberg award.
>> 
>> Tom Droege
>> 
>> At 01:32 AM 5/12/00 PDT, you wrote:
>> >The alchemist cannot resist---you want simple and inexpensive----
>> >
>> >Cobalt chloride-----------one ounce
>> >Sodium chloride-----------one half ounce
>> >Calcium chloride----------75 grains
>> >Acacia--------------------one quarter ounce
>> >Water---------------------three ounces
>> >
>> >Saturate white blotting paper and hang up to dry.
>> >
>> >Rose red-------rain
>> >Pale red-------very moist
>> >Bluish red-----moist
>> >Lavender blue--nearly dry
>> >blue-----------very dry
>> >
>> >From the old reliable 1907 Henley's Twentieth Century Secret Formula and 
>> >trade processes.
>> >
>> >the other Droege
>> >
>> >
>> >>From: Tom Droege <droege@wwa.com>
>> >>To: tass@listserv.wwa.com
>> >>Subject: Dry Cameras
>> >>Date: Thu, 11 May 2000 14:43:02 -0500
>> >>
>> >>I have modified two cameras to have gas in and out fittings.  This was a
>> >>pain as I had to drill an tap a 1/8 NPT fitting into a completed camera.
>> >>Hard to keep metal scraps out of the works.  The cameras have been baked
>> >>for a day and a half with dry air passing through them.  They are mounted
>> >>on the telescope, and dry air is circulating.  It has been raining
outside,
>> >>so there could not be a better day to test a "keep the cameras dry" 
>> >>project.
>> >>
>> >>I should know by the end of today if I have solved this "last" problem.
>> >>
>> >>CAUTION!!!   Do not connect the gas flow fittings to the cooling water
>> >>loop.  This will circulate wet water throught the cameras rather than dry
>> >>air.  No, I have not yet made this mistake.  But the fittings are the
same
>> >>(at the moment).   Nothing is ever easy.  A catalog search has not
produced
>> >>a black fitting of the size I need for the air.  1/8" NPT to 1/8" hose
>> >>barb.  The only one I can find is white plastic.  I guess I will have to
>> >>paint them.  There is a light baffel inside the camera, but I would
like to
>> >>minimize the need to block stray light.
>> >>
>> >>Does anyone know a source for a cheap, not too accurate relative humidity
>> >>indicator?  I would like one powered by 5 or 15 volts, and which puts out
>> >>only a modest signal.  The ADC measurement system has a least significant
>> >>bit of 300 micro volts.  Something with say 3mv or more per % relative
>> >>humidity would be fine.  I think I can tolerate almost any scale factor
>> >>that such a device would have.
>> >>
>> >>I would like to sense the relative humidity.  I already sense the
>> >>temperature.  With the two, I think one can compute the dew point.  I
would
>> >>then regulate the cooling water just above the dew point.
>> >>
>> >>Tom Droege
>> >>
>> >
>> >________________________________________________________________________
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>> >
>> >
>> >
>> 
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