Re: [PSUBS-MAILIST] Re: pressure sensors

[andy goldstein <andy.goldstein@videoray.com>]

Jens,

Very nice!  There is something inherently beautiful in a large 
mechanical gauge.  I'd probably trust it to be accurate to a few meters. 
 We recently did comparison tests against 2 grade 1A mechanical gauges 
and found the both mechanical gauges to be off by about 10 meters 
equivalent at worse case.  Could have been temp effects or aging though.

It's pretty easy to convert a Bar gauge to Meters depth, you can almost 
just draw a 0 after each number.  1 Bar ~= 10 m.  Americans will have a 
harder time ;)

I'll play devils advocate in the mechanical vs. electronic gauge argument:

1) You're mechanical gauge has small metal bits inside that are also 
subject to corrosion.  I feel more confident in my g-shock watch than my 
mechanical omega (even rated to 300m) in rough environments.

2) It's easier to replicate the display of an electronic gauge, so both 
pilot and observer can see the same data.

3) It's easier to telemeter an electronic gauge to the surface.

4) It's easier to switch units (meters, feet, fathoms, etc.) or 
languages on an electronic gauge

5) It's easier to trigger alarms (safe depth exceeded).

6) It's easier to integrate with a deco computer for an ambient sub

7) It's easier to correct for atmospheric pressure

8) It's easier to correct for water density (fresh/salt/etc.)

9) It's easier to integrate multiple electronic sensors into a single 
instrument (depth, temp, altitude, compass, etc.)

10) It's easier to use an electronic sensor in an automatic controller 
(for example, to automatically hold a depth)

11) An electronic sensor can just as easily drive a large analog gauge 
face (using a servo or stepper motor) or a digital readout.

12) It's easier to make a log from an electronic sensor (for stuff like 
dive profiles).


All that being said, I'd think your Tiefenmesser will be fine, and it 
does look great.   I'd also love to see of full snapshot of the colored 
mechanical drawing you used as a background for your gauge photos.

-a








Jon Wallace wrote:
> Nice work.  Nothing wrong with an analog instrument, especially a big 
> one that is easy to read.
> Jon
>
> Jens Laland wrote:
> > Here is a few images showing how I converted a 160mm (6-1/16") OD german
> > Tecsis 0-10 bar class 1.0 pressure gauge into a 0-100 meter seawater 
> > depth
> > gauge (Tiefenmesser).
> >
> > ftp://ftp.artematrix.org/personal_submarine/instruments/diy-mod1_160mmOD-Tecsis-gauge.jpg 
> >
> >
> > ftp://ftp.artematrix.org/personal_submarine/instruments/diy-mod2_pull_needle4.jpg 
> >
> >
> > ftp://ftp.artematrix.org/personal_submarine/instruments/diy-mod3a_dial.jpg 
> >
> >
> > ftp://ftp.artematrix.org/personal_submarine/instruments/diy-mod4b_modified_10-bar_pressure-gauge.jpg 
> >
> >
> > I would be very interested in your comments about using and trusting such
> > a product.
> >   
>
>
>
>
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