[Mal Bridgeman]

Liam

Been thinking some more about this.

First thing is to check the NDLs for each computer for each depth when they are "clean". Variance at this point will indicate likelihood of difference later.

Next is to compare the depth readings. It's unlikely they read exactly the same ..... the one that reads slightly deeper will use up ND time more quickly, obviously. Does the variance differ the deeper you get?

Finally when you compared the remaining NDLs were you at *exactly* the same depth. Depending on where you are in the computer's model of your dive and what was the controlling "compartment" will have a bearing. If you went up or down a metre, would the NDL change significantly?

It's why diving to the limits of a computer is really not to be recommended, especially when the decompression algorithms are ...well .... rudimentary

HTH
Mal