Slightly different answers!! Bugger!

[edneeves]

I have just bought a PADI Wheel and have been completing the last few questions in the PADI workbook ready for my DM.

The problem I have is that the answers I am getting vary slightly to the answers in the book.

I have worked out that the problem is where the pressure groups line cut the depth line, I am taking the first line that actually cuts the line (even though it is by a small margin), however the book says that the currect pressure group is the line after that (the one that cuts the line by an extra margin).

I have checked the wheel and all the circles and dots line up ok.

My questions are these;

Does it matter to what degree of accuracy my wheel is reading?

Is it ok to have a margin of error like this?

If not would PADI swap my wheel for a more precise one?

 

[Jason B]

What is the problem you were working out. I'd like to try it on my wheel and see what I get. In fact don't tell me the answer...just the question. That way we can see if I call it like you or PADI.

 

[Kim]

Does your arrow really cut the line - or just touch it? If you have the Wheel manual handy - check pages 22 & 23

 

[edneeves]

The one above touches with the end of the line, so I naturally take the next one which is only just cutting.

Padi then informs me that I wanted the next one. Its very frustrating when I have just paid for my brand new wheel!!

I am at work at the moment Bubble Blower, when I get home I will write up your test and we will see how you get on...

Ed.

 

[MikeFerrara]

It's fairly common for two weels to be off by a minute or a pressure group. It doesn't matter for diving but can when taking a test.

I don't remember any borderline problems on the DM decompression test though. If you're confident in your ability to use the weel, I wouldn't worry.

 

[edneeves]

I am totally confident in using the wheel, thats the frustrating part! I know my methods are correct but someone (the book) is telling me otherwise.

Ed.

 

[MikeFerrara]

I am totally confident in using the wheel, thats the frustrating part! I know my methods are correct but someone (the book) is telling me otherwise.

Ed.

As I said...on borderline problems you will get slightly different answers from one weel to the next.

 

[edneeves]

Here's the question, if any one wants to have a go, we can then compare answers and see how much wheel variation we get:

A diver exits the water at 1:30pm after a dive to 19 metres/63 feet for 34 minutes. He re-enters the water at 2:20pm for a diveto 17 metres/55 feet for 24 minutes. How soon could the diver re-enter the water for a dive to 15 metres/50 feet for 40 minutes?

Your time starts now!

 

[Kim]

37 minutes.

End of dive 1 = O

50min SI = F

End of dive 2 = R

Required PG for last dive = J

SI = 37

I hope I've done this right - I have my 1.5 year old daughter running around here!! I'll check it again later!

 

[Jason B]

Here's what I get...
First dive....63 ft for 34 minutes = P
Surface Interval for 50 min = G
Second dive.....55 ft for 24 minutes = R
Third dive requires diver start dive as a L diver, which means he needs a SI of 26 minutes.

My wheel is about 13 years old...