HID Wierdy....

Andy M

Doesnt the meg have a computer in the head as well as in the handset? In which case it is possibly unique amongst rebreathers as there is a clocked digital bus between the two parts. The EM field wouldnt affect the Inspiration because the computer is all contained in the handsets. Not sure about Vision? Cis Lunar?

__________________
Know your PO2 at all times

schford

Andy there is no computer in the hand set in the Meg - the 2 ccomputers are in the head. the handset has a display and some buttons only...

I think you might be on to somethign though as Leon said that the flashing red green red green means that the HUD computer is out of calibration and if it will not then claibrate it is out of synch with the shearwater and the way to fix that is to switch them both off then both on then recalibrate.

Andy M

OK. Let me rephrase, there will be a microprocessor in the handset. because something has to convert the signals from the head unit into the digits on the LCD display...

__________________
Know your PO2 at all times

schford

The Shearwater works fine though - no errors at all, wrist mount display tracks PPO2, deco obligation etc etc perfectly.

The problem was with the HUD which is controlled from a sperate computer...

Stuart

divingniknaks

As promised feedback from Barry.

"He has no knowledge or any previous reports of the HID affecting Rebreather's. "

I guess that doesn't help too much to throw any light on it, but I did say I'd ask him.

Phill

bgpartri

The Meg main unit signals the HUD across a wire when it wants it to turn on or off, or to calibrate. The signal is precisely timed, and the HUD will ignore any signal that doesn't go on and off in the right times. For example, to cause a calibration, the signal must go on and off in 100 uS, then go on again in 200 uS. There is no communication from the HUD to the main computer.

I put the timing in so that turning off the main computer or having the battery fail wouldn't turn off the HUD. And it doesn't. However, I didn't plan for active jamming.

The HUD is receiving the calibrate signal, and can't calibrate successfully, so it displays the calibration failure signal.

I've tested my Meg with both a DiveRite and a Sartec HID and can't duplicate the problem, so I suspect that the light in question radiates a lot of interference. That could be because of the design, or maybe just because of the power. I'll dig out my dual 24 watt Halcyon video lights, charge them up, and give that a try.

An RFI shield in the form of a copper or aluminum piece of metal, or one of the sprays or paints available should fix it. But I have no way of testing it because I can't duplicate it.

BTW, the communication from the controller to the handset display is plain old low speed serial.

Bruce Partridge
Shearwater Research Inc.

caveseeker7

For years now I had to listen to people saying that the military testing performed on the PRISM Topaz and Invader didn't apply to civilian divers, that those tests, including EMP testing, are not important.

I truly hope some of these naysayers are reading this thread, as it should change their mind. With electronics for underwater lighting getting ever more powerful, these effects should have been and need to be taken into consideration. We are talking about a life support system here, and using cameras and lights is a common reason for the use of rebreathers.

At first I considered to respond with a new thread in the PRISM section, but as this is the General Rebreather Forum and the subject fits, here it is:

The PRISM has passed full IV & V (Independent Validation and Verification) by the NAVY and to their standards. Even a coast guard flash fired into the battery/electronics compartment did not harm the electronics or prevent them from operating. At 10 volts/meter the electronics kept working and didn’t even need to reset.

The maximum exposure was 200 volts/meter. That's enough power to light the LEDs in the HUD up (even with the battery physically removed), but not enough to damage the electronics or prevent the unit from resetting itself, being fully operable within seconds and without operator action.

__________________
Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"

UWSojourner

Did the life support system fail? Did the handset disintegrate? Did the electronics fry?

Sounds to me like the HUD required reset. But I guess a little hyperbole never hurt anyone.

caveseeker7

Did I say that anywhere? No.

Did the computer reset itself and continue to monitor the pO2 and control the O2 addition?
No. And apearantly not for 24 hrs.
I do call that a failure. Just my opinion, though.

Stuart gave the answer to this and the above question.
Sounds to me like something that you wouldn't want to happen during a dive.
A reset that requires the primary and secondary electronics to recalibrated.
At what depth do you usually calibrate your rebreather?

And maybe more importantly, do you know that this couldn't happen UW?
It wasn't commercial or military hardware that triggered the failure, but a dive light.

I'm perfectly aware that the majority of people do not even remotely care about that sort of thing,
but I find it suprising nevertheless. My intent is not to bash the Meg or Shearwater,
but I do find a failure such as this disappointing.

Someone earlier in this thread commented on the Inspiration, and asked about
the Vision and Cis. So I assumed the discussion included other units.

__________________
Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"

UWSojourner

Maybe not, but you clearly attempted to raise concern about its appropriateness as a life support system . While doing so you then tout a military study that must have supported the idea that a nuclear device was detonated next to PRISM - and the thing survived and protected the diver too ( Wow, turns out I can do hyperbole too !)

I'd like to see the military study though. Sounds interesting. Do you have a copy, or a website, I could get for review?