a new sensor holder

My First home Made sensor holder En Français

The sensor holder one can see above is the first I built, it was located on the inhalation hose, made out of a pvc cross we had glued 2 pvc hose union fittings on.

Sensors were located in two ends of the cross, this system was simple and has worked fine, I’ve used it for a years.

The main asset of this device was the possibility to remove quickly the sensor holder and the ppo2 handset from the rebreather to put it away in a dry bag without having to take the rebreather to parts.

the pictures below show how to remove the sensor holder from
the breathing hose :

Same thing below along with my first resin moulded ppo2 and set.

This sensor holder had his 2 sensors in the gas flow coming directly from the counter lung so that the ppo2 displayed was exactly the breathed gas ppo2 .

In case the loop drowns the sensor being at the highest point of the loop they are likely not to take a salted watter bath .... at least I hope so ....

In term of humidity I think this location is not mabye not the best, as a matter of fact I’ve often noticed a lot of condensation but as I never used a canister located sensor rebreather I am not able to say if this sensor location is better or worst then other options.

I tend to think that all rebreathers suffer from general humidity.

I did not keep this pvc sensor holder only because I wanted to use 3 sensors even if i had dived ccr using only 2 sensors for quite a long time.

As a consequence I bought a Tecme sensor holder one can see on the home page pictures.

This sensor holder worked well but it is a little bit difficult to revove it from the breather, and one can’t do it without disconnecting the inhalation hose from the inhalation bag port.

What I need is to be able to remove the sensors, the canister in 1 minute and to rince the rebreather in 2 minutes arriving at the harbour.

I don’t want to spend 20’ to clean my rebreather, I don’t have time and it is not a game for me ...

in addition as the tecme sensor holder is fitted in the 35 mm diameter dolphin breathing bag port, the sensor holder intake pipe has a 26mm diameter .

I suspect this diameter restriction to increase my breathing work, well I am not sure of this as I have no breathing machine to evaluate the effect of this restriction.

For those reasons Nicolas and I started designing a new sensor holder.

Well now less talk more pictures :

this is of course only a prototype made of pvc only because it is an easy plastic to glue, but it is a nasty plastic to machine.

When it is finished and tested I will make new ones from epoxy resin moulded and then
turned on my chinese cheap lathe.

Denis could not resist long, I gave him the parts yesterday for the internal ultimate milling work he put everything all together this morning !

the tests will be done tomorrow I think, here are the pictures :

If the tests are satisfactory i will have to make a new epoxy cape, but back and to paint the pvc black cause the toilette pvc hose colors is really ugly.

I think I will built a transparent sensor holder or a delrin one

Denis performed the tests diving the rig with the new sensor holder today the 5th of august 2008, good test pilot ...

The sensor holder performed perfectly it’s duty

In spite of the fact that the sensor holder is located on the breathing hose denis did not notice any difference compared with the tecme, the sensor holder does not pull the breathing hoses.

the sensor holder keeps an horizontal attitude, Denis did not notice any wob increase .

wob is not better then the tecme sensor holder, mabye will we notice a difference under high effort.

The new sensor real make a difference during the post dive opérations.

the diver removes the sensors holder cape along with the sensor (attached on the cape) the cable and the hanset, he removes the canister all in one minute, the diver takes off the breathing bags capes and the intake watter via the sensor holder body, the water get in the inhalation side and in the exhalation side that in both brathing bags.

then the rebreather is stored in it’s uprigth position drying by itself and it will take only a couple of minutes to be prepered and tested before the next dive.

It is no more needed to carefully lay down the machine in order to undo every part one after the other to clean each part separately and the to put everything back together .

I’ve only had a diver in my nine years if rebreather diving but I’ve noticed that all the plastic parts have been damaged by the numerous assemblies and dessassemblies the original configuration forced me to do over the years (after 6 years I had to buy new bags and hoses) .

the majority of the rebreather parts stay in place and the rebreather is simply stored just like a twin tank set.

on the other hand the tecme offers the diver an easy of acess to the back of the sensor for sensor connexions checks, our new sensor holder will force us to unscrew a nut and remove the sensors to reajust or clean the molex connectors in case of a loss os signal....so everything has pros and cons