Problems going from v1.80 to v1.90..

[olibert]

I enjoy very much the new logbook viewer and the future decotime features in v1.90 but I am worried about some changes in behaviour:

- the depth calculation has changed. I dive in sweet water and in v1.80 I always had a bit more depth than my other computer that is fixed at sea water. Now, since I installed v1.90 I get the exact same depth reading. And salinity is set to 1.00. Why has depth calculation changed? Other colleagues with OSTC verified this too: they get a reading like if it was salt water...

- you cannot adjust the depth for the (G1) (first gas). It is fixed to 0m. I remember changing this on v1.80 so I could choose the max ppo2 I wanted to be exposed to and seeing the ostc calculated depth..

Are those changes on purpose? Or colateral damage??

It just made me think: how formal is the testing process before a new official firmware is posted? are we testing OC/ CC, Air, TRMX, single gas, multi gas, GF, no GF, etc? I love new features but I will panic and slow down the updates if I get the feeling things get broken now and then.

Anyway, just healthy questions: please don't take this as bad criticism..

Thanks,
Olibert

[heinrichsweikamp]

Hi,

> - the depth calculation has changed. I dive in
> sweet water and in v1.80 I always had a bit more

Correct, there was a minor bug primary affecting cold water. The 1.90 reading is more accurate. However, the difference is small.

> - you cannot adjust the depth for the (G1) (first
> gas). It is fixed to 0m. I remember changing this
> on v1.80 so I could choose the max ppo2 I wanted
> to be exposed to and seeing the ostc calculated
> depth..

That was intend (First Gas starts at 0m). After some complaints about this, we changed it again in 1.91 (Where you can freely choose the depth again).

> process before a new official firmware is posted?
> are we testing OC/ CC, Air, TRMX, single gas,
> multi gas, GF, no GF, etc?

Yes, all of the above. With the simulator, in the pressure tank and during real dives with a lot of input from the community. We go diving a lot, too.

Cheers,
Matthias

[olibert]

Thank you Matthias for your thorough response!

I am satisfied with your comments except with the first one "The 1.90 reading is more accurate.". I have compared different depth meters against v1.90 and I have the impression that readings are lower than they should be. Example:

dive in sweet water
digital gauge depth = 82.6m (they assume salt water 1.03)
suunto HelO2 depth = 82.9m (they assume salt water 1.03)
mk2 v1.90 depth = 82.7m (salinity set to 1.00kg/l)

Based on my previous dives, I believe that with mk2 v1.80 (salin=1.00kg/l) I would have a reading of ~84.6m (which is quite logic)

I set, just to test, the mk2 to Salinity 1.03kg/l to compare to other salt-water computers I get a depth reading clearly understated... I really believe something is wrong. Is it possible that something was missed?

Thanks for looking into it and kind regards,
Xavier

[olibert]

Hello Again,

I have tested again on sweet water, this time against a new Mares Icon set to sweet water and a Suunto HelO2 with default salt water calibration. The OSTC, set to sweet water, is giving me shallower readings. Same depth readings, or slighly shallower, than the HelO2. So those are "salt water readings". The Icon indicates the real sweet-water depth, deeper than the OSTC or the Suunto.

I will repeat this test after resetting the OSTC to v1.80. This will allow us to compare figures from same ostc hw with different sw version. I will send the full set of figures if needed..

Regards,
Xavier

[sailor]

sweet water = fresh water ;->

[tiefunten]

As far as I know, the guys from Heinrichsweikamp have a pressurized chamber to test the computers. I'm quite convinced that the ostc depth reading is more accurate than that of the HelO2 unless the manometer of the pressure tank is broken. Maybe you can shoot a buoy on the next dive with a correctly measured lenght of line and compare this with your depth readings?

[olibert]

Hi tiefunten, sorry but that, I think, wishful thinking... (no offense!) It is not an HelO2 I am comparing to but also 3 other gauges and event the exact same OSTC with v1.8

The problem I report is not HW related. It is a SW change introduced somewhere between v1.8 and v1.9 that over-corrects depth readings. If our friends at Heinrichsweikamp set a chamber to 8.00bars they will quickly see that the mk2s (with salinity=1.00) are reading closer to 68m than the 70m it should be..

[heinrichsweikamp]

Hello,

As discussed intensively here: http://www.heinrichsweikamp.com/read.php?2,4224,page=1 we precisely followed the sensor manufactures procedure for pressure readings. In 1.80 was a bug leading to a small error in cold water, in 1.90 this is corrected causing a slight different reading.
In the OSTC 1bar pressure increase equals 10m depth if salinity is set to 1.00kg/l

Regards,
Matthias

[olibert]

Thank you Matthias for the precision. But let me ask: Have you really verified on v1.90 that "In the OSTC 1bar pressure increase equals 10m depth if salinity is set to 1.00kg/l"? I don't have access to a pressure chamber but my field tests prove this wrong..

Regards,
Xavier

[fishwithlungs]

>In the OSTC 1bar pressure increase equals 10m depth if salinity is set to 1.00kg/l<

I recall from my training(long ago,with depth gauge on a console) and so I pass on to my students now that 1bar pressure change equals 10m depth change in salt water,in fresh water is widely accepted 10.3m depth change for each bar.Average salinity in oceans is around 35 g/l,so that would logically suggest only 9.65m depth change if salinity is 0 g/l.Further that leads to assumption that OSTC with salinity set to 1.00 is in fact ready for your average saltwater.That would be consistent with different gauges and computers calibrated for salt water that I have used alongside OSTC,

Greetings,
Richard

[olibert]

Richard, spot on! you're right 1bar = 1.0197Kg/cm2 , therefore:

a 10m column of fresh water weights 1Kg
1Kg/cm2 -> 0.9804 bar

so, according to Matthias' statement "In the OSTC 1bar pressure increase equals 10m depth if salinity is set to 1.00kg/l" identifies the problem.

the correct statement would need to be:

"In the OSTC 1bar pressure increase equals 10.2m depth if salinity is set to 1.00kg/l".

That 2% increase would fully explain the discrepancy I observed with multiple devices.

Matthias, does this make sense? Is this 1.0197 factor something you guys could adjust in a future version??

Thanks & Regards,
Xavier

[tiefunten]

Hi,

it seems to me, that Heinrichsweikamp simply forgot to include the "Ortsfaktor g" (apparent gravity?). As F=m*g that means p=F/A=m*g/A. With a salinity setting of 1.00kg/l that means in a depth of 10m: p=10m*1000kg/m[sup]3[/sup]*9,8m/s[sup]2[/sup]=98000 N/m[sup]2[/sup]= 0.98 bar. Matthias: could you please correct this before 2.0 stable?

Cheers,

Jörn

[olibert]

Matthias,

would you like any more data to be convinced of the issue? or you are
already convinced and scheduling a bugfix?

Thanks and regards,
Xavier

[tiefunten]

@olibert: Hi, it is already corrected: http://www.heinrichsweikamp.com/read.php?2,5645
V1.95 beta and later will show an increased depth of approx. 2%.

Cheers,

Jörn