Hello Dive Nut NY,
Sorry for the delay in response. We do monitor the Scuba Board and enjoy getting feedback and also answering your questions. Thank you for bringing this thread to our attention by contacting us via our Customer Service section of our website.
In response to the original thread...you are seeing a longer NDL at the 40 depth with a Bühlmann algorithm computer (NiTek DUO) versus a RGBM-based algorithm computer (Suunto). This is based on the science of the algorithm and there is nothing wrong with either computer.
It is difficult to evaluate a computer and deem it too conservative based on this one data point. Truly, you must evaluate the difference between two different scientific algorithms and select the one that you believe will work best for you. Neither algorithm is better, they both try to achieve the same goal of allowing you to safely surface from a dive without dangerous levels of residual nitrogen that can lead to DCS.
Since you are diving within recreational limits it may be that your friends RGBM-driven computer is giving him credit for slowly ascending. It may be considering his ascent a deep stop so-to-speak and allow him to stay down a few minutes longer. The Bühlmann algorithm may not give that same credit as the algorithm may be considering that slow ascent as still deep enough to be on gassing nitrogen. Therefore, the Buhlmann algorithm would shorten the dive to stay within NDL or put you into deco. It is hard to tell based on the information provided.
In your email to us today you wrote
[FONT="]When I bought this computer [NiTek DUO], I thought I was buying a computer that would handle Tech Diving To me, Tech Diving is pushing limits. This device is so conservative I can not do a Tech Dive without making the computer unusable due to the programming.[/FONT][FONT="][/FONT]
You went on to write that you did a 90 foot dive and you had to surface six minutes before your dive partner. If you are diving within NDL, then you are not tech diving. In tech diving, we routinely take calculated risks with plenty of conservatism to perform dives beyond NDL, beyond recreational depth limits and into overhead environments. Our goal is not to push limits by taking risks, but to take calculated risks based on training and education. A tech diver would go ahead and do the extra six minutes at 90 feet, if it was important for the dive mission, and then stay an extra few minutes to wash out on deco.
Please do not confuse lack of conservatism with tech diving. Tech diving is very conservative if approached safely and with the proper training.
This is a fairly complex subject for a board discussion. The bottom line is that more bottom time is not necessarily better. The best advice we can offer to help you understand the difference between algorithms is to enroll in an Advanced Nitrox and Decompression theory course, which is beyond the scope of this thread.
Please let us know if you have further questions. Thanks again for contacting us and allowing us the chance to educate and assist.
Safe diving,
Kathleen