sensor signal loss mystery

jmurba

Hi all,

Last week end I was at the cavalaire (france) tech festival for a slight overview of nowdays rebreathers.
I talk to a couple of professionnals and divers using various ccr user's trying to understand what remains for me a little bit mystérious : the sensor signal losses.
here is the story, like many I convereted my first dolphin home building a simple oxymeter, I means 2 voltmeters, 2 pots , a pvc sensor holder lade in hal an hour, 3 simples cables in a watering hose going from the pvc sensor holder to a pressure oxymeter houssing......
This device worked whitout a shadow of a problem, with it I never ever met any sensor signal loss underwater.
I just even think I could see my display zeroing underwater for an other reason then a failure or the sensor itself.

Like many others I bettered my home made oxymeters, making a digital circuit, a one atm houssing, and installing disconnectable lumberg and others cables/connectors IP68/M12 .

My problems began there...ok the gauge is fine , big buzzer, hud, etc etc etc but from time to time we lose the signal....

we started suspecting the sensor connectors (the molex) , we changed it , we protected then etc....we still sometime lose the signal...

so we went on suspecting the lumberg connector but we found out that no water went in the connector.

After a further trouble shouting brain storming we discovered that after havin cleaned the lumberg connectors we had less problem, a slight oxidation on the male pin of the connector was detected...

Well anyway it works but sensor signal can be loost underwater which it not really reassuring.....

In cavalaire I spoke to the present ccr user lads arround and all told me that this problem is common...

Jacques vettier suspects his sensor connectors (the one plugged on the sensors) and the apther make various assumptions to reduce the probability of lossing the sensor signal....

Jacques was telling me that for example he had never lost the signal on his hs explorer where he happened to lose it on his revodream sharing one sensor with the hs explorer dive computer... an aother mystery


all of that only learnt me that the problem affects a wide range of ccrs...but my main question was not answered .... why the hell i had never ever faced this problem with my former simple basic home built oxygauge....

knowing that I am not alone in this situation is not satisfactory (((-:

Does it come from the disconnectable cable/connectors, is it better not to use a connector and to go directly from the cell holder to the gauge using potted cable glands ?

I don't know.

for the moment we are going to gild our molexs, and connector pins but will it solve the system ?

what I would like to know is who among the community has no sensor signal losses with is system, and how the system is built ?

is guys never lose their signal on their Rebreather it would mean that there is a solution that I still did't find....

help ((((-:

regards
sorrry for the long post

jean mi

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when will I be able to think about something else then spending hours underwater, when will I be normal ?

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jhaaja

In general connectors seem to introduce weak point on the signal path. They can get corroded etc. Hardwiring seems to work a lot better.

I have had no problems with classic YBOD or the HH but have has some trouble with 4th cell + VR3 (the Fischer connector)

JH

jmurba

Hi
Interresting, sorry for my ignorance but what is the YBOD ?
As a matter of fact I fera it comes from the connectors...
the only problem in my case is the the lumberg connector receptacle mounted on my oxygauge houssing is potted (I don't have to do it myself) and makes my houssing one atm.
the second problem of getting rid of connector is the impossibility of changing the gauge at the last moment in case of a problem coming from the gauge (as I built my oxymeters I have many) .
in addition if we get a problem in the wirer or the sensor connector that make it necesseray to change the cable, it will be more difficult to change it ....
well...
regards
thanks
jmi
jean mi

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when will I be able to think about something else then spending hours underwater, when will I be normal ?

http://web.mac.com/jmurba/Site_2/home.html
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David Pye

YBOD = Yellow Box of Death aka Buddy Inspiration CCR

jhaaja

YBOD = Inspiration Rebreather

One connector possibility might be Subconn connectors. It is always a trade of when choosing either connector or hardwired, both have their advantages/disadvantages.

JH

gibbogeo

I had signal loss on one of the three cells of my classic kiss. The problem was the crimping of the molex connector.

I changed the molex connector as suggested by paulraymaker: cut the tipof the cable (the one oxydised) sold the cable, crimp it to molex connector, resold the crimping. and the problem disappeared.

Why dont'you write something about the Cavalaire teck week?

jmurba

yes but the problem in général does not always come from connectors , as I was saying previously one of my friend was telling me that he had necer lost the signal of hs explorer sharing one sensor of his revodream that lost this sensor signal....

the question is how oftent does it happend on ccr's in general ?

are there ccr that never has those problems ???

regards

jean mi

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when will I be able to think about something else then spending hours underwater, when will I be normal ?

http://web.mac.com/jmurba/Site_2/home.html
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jmurba

Hi what do you mean by crimping and tipof ...sorry I did not understand

regards

jean mi

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when will I be able to think about something else then spending hours underwater, when will I be normal ?

http://web.mac.com/jmurba/Site_2/home.html
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jmurba

Schford out of topic sorry just to anwser gibbeo

in fact i did not really participate to the conferences, i went there just to dive and to try to get info about new computers (no one was displayed)
I just lingered a little bit among the different stands and talked with a couple of exhibitors.

others will certainely talk about this festival

the togo is still in the cavalaire bay (((-:

regards

jean mi

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when will I be able to think about something else then spending hours underwater, when will I be normal ?

http://web.mac.com/jmurba/Site_2/home.html
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Stephane

Crimping a soldered cable is not the way it must be done. Either it's crimped on bare wires and then soldered (but take care of not heating too much as the cable insulator might retract too much) or wires directly soldered on the pin.

I have a bad issue with one of my rEvodream, I'm too loosing the value during the dive (I start OK with 3 cells then few minutes later one cell disappear).
When I play with the wires near the Molex connector, I can reproduce the problem.
So yesterday I found in the electronic lab some different pins (AMP Modu) which I think have a far better contact than the Molex one. Now I can bent the cables, I don't loose the cell anymore. The contact is all gold plated, not only on the surface that comes in contact with the pin on the cell.
Oh, and what I do to prevent moisture coming into the cable is to pot the crimped part with glue.
I will try to post a photo tonight.

__________________
Stéphane