Best rEvo sensor configuration?

[NAND]

@tbone1004 Thanks for this info, was already wondering

@stuartv

While sharing sensors is possible it increases the risk of losing your information validity during dive. In every circuit are weak spots (Eg. Fischer-connectors etc.) which may short out or receive voltage from other sources and produce errors.

It comes back to the point where Eg. one computer floods and the other computers information can not be trusted anymore due to voltage transferred from the shared cable, leaving you with the only option of bailout. Now there may be bugs or defects noone yet can forsee leading to such 'dont trust any of them' situations.

I started ccr diving when single cell sensors were state-of-the-art and most manufacturers introduced either a second PPO2-monitor or the three cell concept. My experience is there are more possible sensor error than only the current cap happening after time. Faulty connections, corroded pins, broken wires etc. may give you really confusing readouts.

Fact is: One computer reporting sonsense on a cross-wired system lets you doubt the other as well.

Having independant circuits enables you to simply throw one unit out and end the dive safely.

On the issue of sensor rotation, Paul wrote on this issue some years back, worth reading if you will be on a rEvo for a while, here and here. I must blame myself to equally behave like @Tassi Devil Diver explaines, there are different opinions on the topic...

 

[stuartv]

Thanks, everyone, for all the ideas.

I had a longish conversation with tbone last night, too. Thanks again, Tom!

So, with all this input, what I am contemplating to do is this:

Run 5 sensors. 3 dedicated to the controller.

Run the other 2 sensors to the HUD.

Remove the Fischer cable Predator completely.

Use my Perdix AI in CC mode as a backup computer.

Put Perdix transmitters on the 1st stages, so I can monitor CCR cylinder pressure on my Perdix.


Some of the benefits I perceive (which could be wrong! so please tell me) in doing it this way are:

- if 2 sensors on the controller are off, but the same, then the voting logic will have the controller calculating the wrong deco*. But, I can set it for a low setpoint and fly it manually based on the 1 sensor that is good plus the 2 sensors that are on the HUD. The Perdix will still calculate a valid deco schedule.

- No sensors are connected to more than one monitor, so none of the electrical issues related above.**

- The HUD has 2 independent sensors that I can read, so I can still fly the unit manually, even if the controller totally dies or if 2 sensors on the controller go bad in the same way.

- The Perdix AI will display a critical alert if I were to do something like splash with my O2 turned off. I *think* that, in the case, presuming the 1st stage was charged, I would splash with a "good" pressure reading. But, as soon as the O2 solenoid fired once (or a few times?), the 1st stage pressure would drop and the Perdix would display the alert then - which should be well before the loop ppO2 becomes hypoxic.

The only real downside to this plan, that I can see, is that I would have to manually maintain the setpoint setting on the Perdix. If I kept the Predator with the Fischer cable, it would have realtime ppO2 data and I would not have to manually do anything with it if/when I change the setpoint on the controller.


* this does yield a question, for which I need to go read the Predator manual. Is there a way that I could "turn off" two of the sensors on the controller, so that it would maintain the desired setpoint using just one sensor? If so, then the case where I determine that 2 sensors are bad and the controller is voting out the one good sensor, I could just disable the 2 bad ones and let it still maintain my setpoint for me. Thus, both keeping my task loading minimized and ensuring the controller still calculates the correct deco schedule.

** regarding the electrical issues with using a splitter: Is this a real world problem, or a theoretical one? Meaning, have problems actually been seen in the real world from this? On units that have been maintained properly?

 

[Schwob]

I just bought a used rEvo....

Congrats!!!
And please, pretty pretty please keep posting your noob rebreather experiences ss they progress... moments of insights, difficulties to work through (if any) until the lightbulb went off... etc.
Lurking ... big time...

 

[stuartv]

Congrats!!!
And please, pretty pretty please keep posting your noob rebreather experiences ss they progress... moments of insights, difficulties to work through (if any) until the lightbulb went off... etc.
Lurking ... big time...

LOL Okay. Will do. :-D

 

[tbone1004]

@stuartv

You need to post a picture of the O2 board. IIRC the diveCAN revo's have 3 cells that go to the DiveCAN. This will be your primary and your HUD and there isn't a lot you can do about that. Cells 4/5 were going to a pair of Revo Dreams and may be wired to the Fischer cable, but you'll have to figure out where that fischer cable goes.
If you have 3 cells going to the DiveCAN I would not split them under any circumstances and in that case the DiveCAN does the splitting over digital signals

 

[stuartv]

@tbone1004

I will work on getting a picture, but I looked at it pretty closely yesterday.

I believe that all 3 devices are wired in separately. In other words, I believe the HUD is not DiveCAN and has no direct connection to the controller.

There are 3 cable bundles coming into the sensor tray. One is from the controller and goes into a little black box. Wires from the little black box connect to 3 sensors. The other 2 cables are the Fischer cable and the HUD cable. They each have their own wires that connect directly to O2 sensors. Splitter cables are in there to allow more than one molex connect to attach to the same O2 sensor.

At least, that is how I assessed things when I looked in there yesterday. I need to open it back up and do some cleaning before class on Sunday, so I will take pictures then.

 

[stuartv]

To be transparent, the rEvo I bought is the one Dsix36 posted here in the SB Classifieds last week. It was a real pleasure to meet Dsix36. He treated me very well on this whole deal.

I drove to Fort Lauderdale on Sunday night. Met Dsix36 Monday afternoon and bought the unit. I also stopped by Add Helium and bought sorb while I was there. Drove home. 2000 miles in 38 hours (4 hours of which was at AH or with Dsix36 or taking a short nap in the AH parking lot).

 

[tbone1004]

@Dsix36 Don, help on how this thing is supposed to work pretty please?

 

[stuartv]

@Dsix36 Don, help on how this thing is supposed to work pretty please?

It was his buddy's unit, so Don wasn't positive on how his buddy had been running it.

No big deal, though. My plan is to run it however my instructor tells me, until I complete my certification on it. After that, I will decide for myself on whether to change it up - based on input from my instructor and what I learn here.

 

[RainPilot]

I would have to manually maintain the setpoint setting on the Perdix.

I run 1.2 at depth on my RB but I have the Perdix set to 1.1

As a backup computer, that gives me a conservative schedule to get out with and I don't worry too much about small SP fluctuations. On a normal dive I follow the most conservative computer which is usually the Perdix. With the diving I am doing, the difference is a minute or two, obviously bigger dives will have more difference.

I also have it on auto-increase but manual decrease so I don't end up with silly switches to 0.7 while on deco.