I don't disagree with the value of test data - that is not what I am suggesting.
I do object to the improper use and/or manipulation of quantitative test data and in turn designing regs that test well, but at the expense of real world validity.
In my field as a program and agency evaluator, I frequently encounter people who use data to measure performance but fail to consider the real meaning and limitations of the data as it relates to real world performance. The fact that the performace meansurments or indicators are developed or stnadardized by a government source does not automatically mean they have much more than face validity. They often select those indicators as they are the best they have, not because they are in any sense of the word perfect.
In this case, one of the easiest methods to improve a total work of breathing score is to decrease the effort needed to exhale and that is easily done by using an overly large exhaust valve. Another cheap and easy means to decrease total WOB is to add a flow vave that creates a venturi effect that increases at high flow rates.
The downside is that you can then end up with a reg that has excellent WOB scores but that has a high cracking effort and then tries to artifically inflate the diver. On paper it looks great, but in the real world, subjectively, it breathes like crap.
In effect, there is value in WOB scores, but that quantitative data needs to be tempered with the qualitative performance of the reg as well. In the case of the pre-1998 D400, I don't know anyone who ever complained about it's performance at depth. In my experience it still delivered gas at deep depths, including hard working dives at deep depths, with the same outstanding subjective feel it displayed at lesser depths. Yet, when WOB testng became the rage, none of that mattered as the focus became entirely quantitative. And the truly stupid freeflow resistance standard became the rock on which lesser CE approved regs broke the better ones by requiring some of the best regs around to be detuned to meet it.
There is real value in WOB data, but that value is most often seen in the graph, not the total WOB number. The graph will tell the entire story of the inhalation cycle including cracking effort, exhaust effort and any unnatural positive pressure phases of the cycle. But no one focuses on that, the focus is just on the total WOB number.
I do object to the improper use and/or manipulation of quantitative test data and in turn designing regs that test well, but at the expense of real world validity.
In my field as a program and agency evaluator, I frequently encounter people who use data to measure performance but fail to consider the real meaning and limitations of the data as it relates to real world performance. The fact that the performace meansurments or indicators are developed or stnadardized by a government source does not automatically mean they have much more than face validity. They often select those indicators as they are the best they have, not because they are in any sense of the word perfect.
In this case, one of the easiest methods to improve a total work of breathing score is to decrease the effort needed to exhale and that is easily done by using an overly large exhaust valve. Another cheap and easy means to decrease total WOB is to add a flow vave that creates a venturi effect that increases at high flow rates.
The downside is that you can then end up with a reg that has excellent WOB scores but that has a high cracking effort and then tries to artifically inflate the diver. On paper it looks great, but in the real world, subjectively, it breathes like crap.
In effect, there is value in WOB scores, but that quantitative data needs to be tempered with the qualitative performance of the reg as well. In the case of the pre-1998 D400, I don't know anyone who ever complained about it's performance at depth. In my experience it still delivered gas at deep depths, including hard working dives at deep depths, with the same outstanding subjective feel it displayed at lesser depths. Yet, when WOB testng became the rage, none of that mattered as the focus became entirely quantitative. And the truly stupid freeflow resistance standard became the rock on which lesser CE approved regs broke the better ones by requiring some of the best regs around to be detuned to meet it.
There is real value in WOB data, but that value is most often seen in the graph, not the total WOB number. The graph will tell the entire story of the inhalation cycle including cracking effort, exhaust effort and any unnatural positive pressure phases of the cycle. But no one focuses on that, the focus is just on the total WOB number.
