SAC on Suunto dive Manager

I am running v 2.30 of the suunto dive manager software and I have 10 logged dives on the cobra myself and 50 or so dives from the previouse owner.

I have noticed a coulple of things with the SAC it reports.
First is that on 4 out of my 10 dives it shows a flat red line for SAC on the graph. and on the virtual computer display the SAC figure is static for the whole dive. While on the other 6 dives I can get a SAC figure for any time durring the dive.
On the previouse 50 dives only the 2nd to last dive gives a changing SAC rate. Any Idea why this is?


Also the SAC figure in the Air Consumtion display is always lower than the SAC on the virtual computer display. Any idea why this is? Also if I change the tank size and then recalculate gas usage the SAC in the Virtual display does not change untill I select another dive then reslect the dive again.

Does v1.6 show constant SAC?

Thanks.

Please dont ask what my SAC is

Were any of your dives which show a changing SAC recorded on your cobra?

The cobra only records the beginning and ending air pressure. The dive computer does not record what your tank pressure was throughout the dive, so it can only calculate an average SAC for the entire dive. No software can show your instantaneous SAC without having the raw data to use in the calculation.

The newer computers like the D6 and D9 do record the tank pressure throughout the dive. So when using these computers you can see your SAC at various points through your dive.

-Mark

All dives were on the same cobra.
The cobra does record Tank pressure & depth every 10 seconds ( or what ever sampling rate it is set to) or at least it displays this in the profile window.