Meg Electronics

Steve

Hi team.



Could someone please outline the differences between the standard Meg electronics package and Bruce’s Shearwater package?



TIA

Steve

bgpartri

I can try to help, but I really don't know much about the APECs electronics.

The Shearwater electronics is an integrated decompression computer with setpoint control. The APECs is setpoint control only.

About the only two other things I could tell you that are different is that the Shearwater uses a lot less power and it can be turned off and on from the handset, and there is only one handset.

Bruce

Robert Cook

Steve, my unit is an early APECS - it uses more power than the shearwater and dosen't have a computer (just a D-Timer arrangement). I'm tossing up various upgrades at the moment - Shearwater, Cis scrubber, whole new unit and sell the current one etc,

Thanks,
Robert

Steve

Thanks Bruce and Rob.


Bruce,

Could you please describe the HUD's LED blinking regime? Is it a factory supplied item from ISC or is it sourced from you and retro fitted to the Meg?

TIA

Steve

bgpartri

The HUD displays one orange flash for 1.0

For ppo2's above or below 1.0 it displays the number of points off 1.0 either higher or lower. Higher is in green and lower is in red. So 1.2 is green-green and .7 is red-red-red.

The coding was originally designed by Will Smithers, so I call it Smithers encoding.

I only make circuit boards and software for the Meg. All of the packaging is done by Innerspace.

Bruce Partridge

UWSojourner

cedricverdier

As far as I know, the Shearwater Electronics is a good add-up for the Meg. All the comments I got were very positive.

I just have 2 comments about it:
- AFAIK the calibration is only done on pure O2 (please correct me if I'm wrong). In the APECS electronics, you calibrate on air AND 100%O2. It should give you a better linearity of the cells reading.
- The Shearwater Decompression algorythm is a Buhlmann model with Gradient Factors. It's a good way to incorporate deep stops in a model that wasn't designed for that. Nevertheless I prefer gas phase models (VPM or RGBM) for my deep Trimix dives.

A few weeks ago I asked Bruce about the availability of a VPM-B version of the Shearwater electronics. Sounds like it's coming out in a near future. I guess I'll upgrade my 2 units.

Cheers

__________________
Cedric Verdier
PADI Course Director, ANDI-IANTD-PSAI-TDI-DSAT-DAN-NAUI-CMAS Instructor Trainer
Trimix (CCR and OC) and Cave Diving Instructor Trainer

www.CedricVerdier.com
DIRrebreather member

Skipbreather

Lets take one step back and one to the side. Whether one orders the Shearwater or APECS w/ one’s shiny new Meg is very much dependant how comfortable you are putting all your eggs in one basket. Out of the gate, by all reports both sets of electronics do a superior job at controlling ppO2. So where do they differ?

1. Price- Shearwater costs an extra $2000. This is offset somewhat by the HUD being included in the price vs. a HUD being a $225 extra w/ the APECS. Call it a de facto $1775 difference.

2. Deco- Shearwater does deco, APECS doesn’t.

3. Readouts- APECS has two handset readouts, Shearwater only has one + the HUD.

Simplified bottom line: For $1775 more, you get deco calculations integrated w/ your ppO2 controller, but you get one less handset. This can be good or bad depending on how much you value streamlining your kit. It is very, very much a personal decision.

Let’s take it another step and consider what that $1775 would buy. As a benchmark, it would most certainly get you the latest and greatest loop integrated color screen VR3 plus the custom sender to feed it. The question of which the algorithm (Shearwater or VR3) performs best is very much a subject that can be debated ad infinitum and is WAY beyond my level of expertise, but most folks would probably admit both will get you safely out of the water if you follow their respective instructions.

So what does it boil down to? For the same cost you can have either a well integrated streamlined rig, or two extra things cluttering up your forearms that give you a second window into what your ppO2 situation is plus a totally redundant ppO2 opinion and deco status. What you choose is up to you and neither is “right” nor “wrong”. Your choice is a solid reflection of how comfortable you are betting your spinal cord- and perhaps your very life- on one integrated set of microchips (“Open the pod bay doors, HAL”) that are a much cleaner overall package. You pays yer money and you takes yer chances.

Best,
Ken

caveseeker7

Excellent post, Ken.

But ordering the APEKS electronics without the optional HUD's gotta be 'wrong'.

__________________
Cheers
Stefan



"It is still a good day if you are on the green side of the grass!

Su amigo Roberto!"

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schford

I had a little play with the APECS electronics in the factory - one thing I prefer (and it is just my opinion) is the user interface on the shearwaters.

The PPO2 read outs are one on top of each other on the APECS on the left hand side of the screen - where as on the Shearwater they are spread across the bottom of the screen and for my money are easier to read.

The other reason I went for the Shearwater is so I have a goodly amount of redundancy - let me explain more.

Shearwater gives me -

1 computer which control deco using GF, monitors the PPO2 across all three cells and fires the solenoid.
2 computer that controls the HUD which monitors PPO2 across all three cells.

I now add a HS explorer to the mix run it on RGBM 1 and the shearwater on 10 / 90 GF (slightly tweaked for each mix) and I have deco profiles that are VERY similar and no single point of failure on my unit.

Bruce makes a quality product!

Stuart