Donovan Parks wrote...

>Here is the setup.  I have a submarine with a differential pressure =
sensor.
>The high pressure end of the sensor will be placed in a 'ballon' that is=
 in
>the water and the low pressure end will be in the interior of the sub.  =
=46or
>technical reasons I can't run a tub up to the surface of the water.

>How do I can this differential pressure into a measurement of the subs
>depth?  Since the submarnie was sealed at the water surface pressure =
(i.e. 1
>atm) and is rigid I am assuming the pressure in the submarnie will =
remain 1
>atm regardless of the depth of the submarnie.  Now, the pressure of the
>'ballon' will change will change will depth as it is non-rigid, but what=
 is
>the conversion factor from differential pressure to depth?  I have a =
book
>(which I don't have access to right now) that gives the relationship, =
but I
>don't really trust the source and it is to 0 decimal places of accuracy!=
  I
>will be using the sub in FRESH water.  (A search of the Internet has =
been
>unfruitful - likely because I am not sure what I should be searching =
for.)

Searching on "pressure conversion factors", google.com pointed me to a
bunch of online units converters.  According to:

http://www.processassociates.com/process/convert/cf_prs.htm ,one foot of
H2O is equivalent to 0.433527516 PSI.

Other than creating an inconvenience for you, the fact that you're using
a differential pressure sensor instead of an absolute sensor is of no
consequence; if the pressure inside your sub starts changing, you've got
more urgent problems than making accurate depth measurements- you're
sinking.

Hope this helps...

Dave

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics