Diference in maximun depth -Divinglog software and OSTC

[david tobin]

The maximum depth on my OSTC MK 2 is different from that shown in the divinglog sofile profile graph and profile data.

Eg OSTC max depth 36.8m
Divinglog lowest postion on graph 38.14 and maximum depth in profile data is 38.14

Why would this be?

David
OSTC 808

[divinglog]

Hi David

What is the max. depth displayed in Diving Log on the first logbook page in the max. depth field? Is it wrong for all dives or just one?

Sven

[dmainou]

What was the salinity setting during that dive?

[david tobin]

Data from previous dives
Date MaxDepth on first logbook page 1 MaxDepth in profiel data Salinity
21/7/10 31.2 31.2 n/a
31/10/10 30.9 31.8 1.03
31/10/10 14.9 14.9 1.01
1/11/10 30.3 30.6 1.02
26/4/11 35.5 36.5 1.04
26/4/11 30.2 31.4 1.04
2/5/11 31.3 32.5 1.04

[Regthing]

The first figure appears to be raw data and the second has the salinity applied 31.3x1.04=32.5

[dmainou]

Yep,

Its the same error that appears in JDiveLog.

The download protocol doesn't include (or didn't include) the salinity setting.

This was actually very helpful back when the accuracy of the sensor was in question.

I believe that HW will be including the salinity setting on the download for the new stable version. That then will allow Sven and Pascal to adjust the depth.

Sven, would you please have a chat with Christian or Jean Do to ensure this is happening?

Thanks mate


Diego

[dmainou]

BTW, If you use a second computer it would be very easy for you to determine its approximate salinity calibration.

Simply divide the reading of one computer over the other.

It won't be 100% accurate as the Mk2 performs active pressure sampling before the dive to determine the surface level. In contrast, most computers simply use the theoretical 1013mB for their calculations.

Therefore the depth readings will be off by approx 10cm for every 10mB (1013mB every 10m).

Of course, then they will also be off by the error in each computers sensor reading.

But will be close enough.

D

[david tobin]

I use a Vytec DS as backup and i carried out the claculation for my last 25 dives.

The value ranged from 1.08 to 1.05 with an average of 1.06

[Regthing]

dmainou Wrote:
-------------------------------------------------------
> BTW, If you use a second computer it would be very
> easy for you to determine its approximate salinity
> calibration.
>
> Simply divide the reading of one computer over the
> other.
>
> It won't be 100% accurate as the Mk2 performs
> active pressure sampling before the dive to
> determine the surface level. In contrast, most
> computers simply use the theoretical 1013mB for
> their calculations.
>
> Therefore the depth readings will be off by approx
> 10cm for every 10mB (1013mB every 10m).
>
> Of course, then they will also be off by the error
> in each computers sensor reading.
>
> But will be close enough.
>
> D


Not quite. You need to know the salinity setting of the 2nd computer. Your method would only work if the 2nd comp was set for fresh water (1.00)

[dmainou]

Regthing Wrote:
-------------------------------------------------------
> dmainou Wrote:
> --------------------------------------------------
> -----
> > BTW, If you use a second computer it would be
> very
> > easy for you to determine its approximate
> salinity
> > calibration.
> >
> > Simply divide the reading of one computer over
> the
> > other.
> >
> > It won't be 100% accurate as the Mk2 performs
> > active pressure sampling before the dive to
> > determine the surface level. In contrast, most
> > computers simply use the theoretical 1013mB for
> > their calculations.
> >
> > Therefore the depth readings will be off by
> approx
> > 10cm for every 10mB (1013mB every 10m).
> >
> > Of course, then they will also be off by the
> error
> > in each computers sensor reading.
> >
> > But will be close enough.
> >
> > D
>
>
> Not quite. You need to know the salinity setting
> of the 2nd computer. Your method would only work
> if the 2nd comp was set for fresh water (1.00)

Hi Scott,

If we assume that the OSTC is accurate (at least yours is). The 1.00 reading of the OSTC it will help determine the calibration of the other computer for that non disclosed "salt water" setting.

That is what I meant.

BTW,it would be awesome to test the seiko's again set to "salt water" just to be aware of how "salty" ys theri salt water calibration.

D

[divinglog]

If I remember correctly, we discussed that when the salinity setting was intruduced in the OSTC long time ago. We agreed that the salinity adjustment is made within the OSTC and the corrected depth is stored in the logbook memory, so we don't have to adjust it after downloading.

I'm doing no salinity adjustment at all (JDiveLog does the same), neither for the max. depth from the dive header, nor for the depth values in the profile. So I assume, the OSTC applies the salinity adjustment just for the max. depth in the header, but not for each depth sample in the profile.

I think it should be changed in the OSTC firmware to keep it identically to the max. depth field and to avoid confusion. But if not possible, I could add the adjustment to the profile parser, of course.

[Bardass]

see the file below

I dived this week with 1.87 Beta

Maximum depth is almost the same between Diving log and OSTC = 39,6 and 39,5m

but not for Jdivelog = 40,05m

My parameters :
salinity = 1,03
2 gaz : air and nitrox 80%

Max Depth

[Bardass]

A bug in Diving Log :
maximum depth is not the same in LogBook and in Data log or profil

logbook Diving Log : 39.6m
In Data Log and profile : 40,7m

Bug maxdepth Diving Log