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Re: [PSUBS-MAILIST] depth gauges
On March 7, 2010 11:09:12 you wrote:
> On the R300, I have a primary and backup depth measurement. The primary is
> a 0-250 psig pressure transmitter (Digi-Key MSP6251P4-1-ND) tied into my
> PLC and touch screen display. This has worked very well as you can
> display the depth digitally and you can switch between sea water and
> freshwater in the depth calculation with a touch of the screen. As a
> backup in the event I loose both my main and auxiliary power supplies, I
> have a Weksler Altitude Gauge (BM43-YHT4-LW). The dial is for 0-450 fsw.
> The problem with a manual pressure gage like this is
> you introduce 2.5% error in the depth measurement when you move between
> sea water and freshwater because of the density difference. As with any
> pressure gage, you need to use a dead weight tester to calibrate the
> instrument.
>
> Cliff
>
Cliff - a couple of questions:
How accurate is the digital gauge in the vicinity of the zero end of the
spectrum. i.e. - Is that sensor as accurate in 0-5 psig as in 120-125 psig?
While it probably doesn't matter for the R300, if someone had a sub in which
they wanted to maintain a periscope / snorkeling depth near the surface, would
there be any merit in also incorporating a higher resolution, lower range
sensor (i.e. 0-50 psig) to be used in that range, and then switching to the
other signal when the vessel is deeper?
I notice that you move your vessel between salt and fresh operating areas. In
the interest of complicating things unnecessarily, it occurred to me that you
could include outboard salinity and temperature sensors to calculate the
density of the water on the fly, and actually create a density profile on the
way down in order to accurately calculate depth, even across a halocline. Fun
stuff.
-Sean
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