SAC Calculation Error
Posted: Fri Mar 13, 2026 6:18 am
I am running MacDive 2.16.3 on a MacBook Pro with current OS. Dive data is from a Shearwater Teric with AI. When I review the plot/graph of RMV, spot check values for both SAC and RMV are about 2x higher than expected. Remaining data seems correct. Comparing a spot check of SAC rates for the same dive at the 30:00 minute mark across Shearwater and MacDive apps results in the following:
SAC Rate (psi/min):
MacDive IOS Spot Check Screen Shot:
Also, I selected a 2 minute window starting at the same 30:00 minute mark. MacDive does not give SAC rate but does give an RMV of 0.66CF/min. Manual calculation yields SAC = 13.2psi/min and RMV = 0.35 CF/min assuming a 80CF tank (which I have double-checked was set for this dive). Screen shot as follows:
Have I somehow got a wrong setting in MacDive MAC version or is there a SAC calculation bug?
SAC Rate (psi/min):
- Shearwater IOS: 15
- Shearwater Mac: 15
- MacDive IOS: 15.34
- MacDive Mac: 27.59
MacDive IOS Spot Check Screen Shot:
Also, I selected a 2 minute window starting at the same 30:00 minute mark. MacDive does not give SAC rate but does give an RMV of 0.66CF/min. Manual calculation yields SAC = 13.2psi/min and RMV = 0.35 CF/min assuming a 80CF tank (which I have double-checked was set for this dive). Screen shot as follows:
Have I somehow got a wrong setting in MacDive MAC version or is there a SAC calculation bug?