Algorithms, Conservative Factors, Altitude, Planned Deco - Questions

[Jay]

...Case in point: all cool kids play vinyl. And if you want lossless audio and are not satisfied with iTunes' selection, CDs are pretty much it. Or you can rip your vinyl into FLACs to play from hard drive.

Hear hear.

... Or you go 192kHz, or rip your DSDs using an ancient PS3 ... just saying

 

[dmaziuk]

I can hear 192Kbps in crapbuds that came with my phone.

 

[CandiveOz]

Just getting back on topic I think I have found the answer to one of my Scupapro questions;

What has your experience been with the heart rate monitor? Do you use it?

Based on a posting in the Subapro forum, for the G2, Scubapro replaced the Polar T31 HRM with their own design which included a skin temperature sensor. Divers have reported problems with the new HRM as compared to the T31. It appears to be a problem with the battery or its ability to function at depth. I suspect it is a water pressure problem which deforms the battery case.
Scubapro Heart Rate Monitor

 

[CandiveOz]

Have you ever had large heart rate spikes during a dive? What was the consequence?

After searching the Scubaboard forums I found two posts that answer my second question above regarding the Scubapro dive computer and the heart rate monitor;
Galileo Sol Troubling Issue
Galileo Sol heart rate monitor accuracy seems poor
Divers have experienced spikes and dropouts using the heart rate monitor (HRM). This was no big surprise since I experience this occasionally with my own HRM on dry land. The consensus is to ensure the HRM is worn snugly and that the contacts are wet. If wearing a dry suit, contact gel works well. Obviously not necessary when wearing a wet suit. Some divers have turned off the workload function for the HRM but still wear it to monitor their heart rate - it helps them to relax during the dive (which is a good thing).

Workload can be calculated by either breathing rate and/or the heart rate monitor. Something that I learned from these posts is that the computer can misinterpret the use of the inflator valve as an increase in breathing - workload. I suppose the same thing can happen if you start purging your reg. The sensitivity of breathing can be adjusted on the computer to mitigate the problem (25 points of adjustment - that's fine tuning!).

Also, if using both breathing rate and heart rate as a measurement of workload but there is a concern that heart rate spikes or inflating your BC would give a false positive to the computer and hence a reduction in NDL or increase in deco obligation, there is a setting in the computer to address these two issues. You can set the computer to select the lower reading of breathing rate or heart rate in real time. In theory any abnormal spike in heart rate or air consumption would be ignored because the lower reading in percentage would be used. So obviously the developers had thought about that scenario.

I now have only two remaining questions to get answers to from my original post.

 

[CandiveOz]

What factors do you take into consideration when setting a MB level. Do you set a microbubble level and keep within its limit or do you breach its limit occasionally or all the time?

I continue searching for answers to my questions in my original post. Most have been answered with the help of SB members but the above question has proved elusive. I posted this question on the Scubapro forum, but didn't get any response.
Scubapro G2 Why 9 Microbubble Levels?
Reading other posts it appears that Scubapro users mainly leave the microbubble level at L0 or maybe go down to L2, but no one has dived L9. In fact I am curious to know how conservative L9 really is and why Scubapro thought it was appropriate to include 9 conservative factors.

 

[CandiveOz]

Is there a way of telling when the computer applies a conservative factor based on the reading from the chest strap? Does the computer use the microbubble level to employ this adjustment? Say for example you enter the water with an MB 3 but when you finish your dive the MB level was 5. And the reason for this was the computer estimated your workload during the dive as high and pushed up the conservative factor/MB level. Is that how it works?

This was the last question to Scubapro users in my post. At the time, I didn't understand how the Scubapro computer informed the diver of an increase in workload and what ramifications it had on the NDL or decompression profile. I initially thought it increased the conservative factors or micobubble levels and forced the diver to follow a more conservative profile. But I was incorrect because while the MB levels are more conservative, the diver is not obligated to follow them. Only at Level 0 (the computer default and most liberal setting) is the diver obligated to follow the decompression profile.

According to the Galileo Sol user manual; "If Galileo detects a sufficient increase in workload, no-stop times can suddenly shorten and decompression stops can quickly grow. To alert you of such possibility, upon entering into an increased workload situation, Galileo warns you with an audible sequence while displaying the message INCREASED WORKLOAD for 12 seconds."

From an article in DiverNet, I also discovered that while wearing the heart rate monitor, the workload alert triggers when the heart rate is 80% of max. The author of the article indicated that he had set his maximum heart rate at 150 and with hard finning the workload alert triggered at 120 (120/150 = 80%). See attached.

Unfortunately the article did not describe by what measure did the workload alert impact the NDL or decompression profile or if there was a delay to allow the diver to reduce his workload before any changes kick in. This specific question remains unanswered.

 

[Jay]

Unfortunately the article did not describe by what measure did the workload alert impact the NDL or decompression profile or if there was a delay to allow the diver to reduce his workload before any changes kick in. This specific question remains unanswered.

I wonder if emailing customerservice@scubapro.com might be a way to answer the question if the SP OZ doesn't know?

 

[CandiveOz]

Hi Jay,
Good idea. I sent them an email. I'll post their response when I receive it.

 

[rongoodman]

Why does Scubapro believe increased work load would affect NDL? I understand that gentle exercise might be helpful during deco stops.

 

[dmaziuk]

Why does Scubapro believe increased work load would affect NDL? I understand that gentle exercise might be helpful during deco stops.

Workload at the bottom w/ no exercise at deco stop does the opposite of gentle exercise at the stop and no work at the bottom. Presumably they've programmed for the former.