MK-6 Electronics white paper.

For your reading pleasure, two sensors or three, it'll make you think.

http://www.poseidon.se/DL_files/MK6_White_Paper_v2.pdf

Hi,

I prefer the simple 3 sensor kiss approach, I think that "humanly" monitoring the 3 sensors is the better way to control the loop ppo2.

if the 3 sensors are the same , in 99.99% on the case the gas loop ppo2 is likely to be close to the ppo2 displayed , in the 00.01% of the case the 3 sensor will give all three a bad info.

if the 3 sensors give all 3 a bad ppo2 it is either because the microcontroller has frozen either because the 3 sensors are blocked by a water vapor film .

Kiss the diver can easily manage this possiblility to be aware of those 2 cases in which the 3 sensors give all 3 the a bad ppo2 .

first of all the kiss diver has to monitor both the ppo2 datas at a given time but also to check that this ppo2 is changing when o2 is manualy injected, when the divers slightly ascends an descends and even doing nothing the diver can track the sligth ppo2 changes if the diplays is able to display enough decimals.

if the diver is able to both check that the 3 sensors displays correct ppo2 and that this ppo2 is always changing a little bit or franckly when injecting o2 then I firmly think that there is very little chance for an error.

of course all this reasonning is based on the kiss "religion" , it means the strong belief that the diver must remains as close as possible from the sensor datas interpreting himself the sensor signal and never let the a softwear interpreting those sensor datas simply reading the résultes of the microcontroller put into the microcontroler.

the simpler the better and the safer.

having read the article you are mentionning I have the impression that it is an other automatic protocol, different from the voting logic but still a softwear, still an interface between the diver and the sensors.

if the diver really want to dive with an automatic O2 injector this protocol may be a little safer because the classic voting logic can't track the 0.01 case in which the 3 sensor displays all 3 a bad data because they are all 3 blocked by a water vapor film, this new protocol will be able to overcome this case blowing dil on a sensor to find out the real ppo2 because the computer both knows the depth (water pressure) and the dil o2 fraction.

on the other hand in case the microcontroller freezes the diver will have no idea of this.

it is also just my own vison.

regards

jean mi















all the best.

I take issue with this passage:


My training with Richie Stevenson covered exactly this point and it was put forward that either a dil flush, or an O2 flush, dependant upon depth and PPO2 in the loop at the time would allow you to ascertain which sensor /s were reading correctly. Never assume it's the two that match in their readings.

I take issue with this passage:

"Suppose you have three sensors that give you readings of 0.5 atm, 0.5 atm, and 1.1 atm. What should the control system assume to be the correct PO2, and how should it use this information to maintain a safe breathing mixture?

Each experienced rebreather diver gave an answer. No two answers were the same. One said the PO2 should be interpreted as 0.5 atm (voting out the high reading as erroneous). Another said the PO2 should be interpreted as 0.7 atm (the average of all three sensors). Another said that the PO2 should be interpreted as 0.8 atm (midpoint between the two values). Another said that the sensor with a dynamic reading should override
the static readings, if any. Another said that the control system should use the low value for preventing hypoxia and for calculating decompression, and the high value for preventing hyperoxia."

My training with Richie Stevenson covered exactly this point and it was put forward that either a dil flush, or an O2 flush, dependant upon depth and PPO2 in the loop at the time would allow you to ascertain which sensor /s were reading correctly. Never assume it's the two that match in their readings.

The point of the text is not "how does the diver know which is correct?" but "how does the control system know which sensors are correct?"
Rebreathers currently are technical dive kit which rely significantly on input from the user. This method is a way to try and remove the need for the user to decide which cell(s) are good and then tell the electronics.

Simon A