The Rebreather Guardian HUD

The Rebreather Guardian HUD
By Mark Chase


In keeping with my ‘Toys Are Us’ tag from Zac I have spent another shed load of hard earnt on a HUD (Heads up display). My main reason for this was that I didn’t think I could trust my self to spend enough time checking my PP02 during an interesting dive. I wanted improved safety and enhanced diving enjoyment and this seemed a good way to get that on a CCR.

This is a ‘first impressions’ report on the unit from Uri and Ill let you all know how I get on with it after a few more dives but for now hers how installation and puddle tests went.

The unit demands a 16mm hole be drilled in the scrubber head. This is no easy thing to do unless you have the right kit but I was lucky enough to have access to a pillar drill and a 5/8th expanding reamer. The type of plastic used in the scrubber is soft and is damaged easily by clamps so care needs to be taken when supporting and fixing down the head. The material also grabs the drill bit so firm clamping is a must. The position of the hole is important but not critical so I guestimated it following a print out of a photo of the unit on Uri’s web site. Doing this it is important to balance the centre hub-fixing ring in pace to get the visual effect required for lining up. Uri is considering a template or axial dimensions to prevent serious errors in the location of this hole.


The actual plug is threaded M16 so it would perhaps have been better to tap the head. The plug is sealed with a single O-ring on the outer face of the scrubber and held in place with a single nut on the inner face. Had I taped the head this would have acted as a lock nut but as it is the integrity of the nut becomes critical to prevent flooding the scrubber. As a result, I have put a blob of Loctite screw lock on it to stop it inadvertently coming undone.

I have the 100m unit but a 160m unit is available. The prime difference being the use of fisher connectors on the deeper unit. Unfortunately, I found out too late that the plugs for the 160m units are smaller in diameter so I can never upgrade to that unit without replacing the head. I concluded that I could do the very occasional 100m plus dive and just not use the HUD but I will have to confirm this with Uri. Suffice as to say if a dive much deeper than 100m enticed me to come I would not quibble at getting a blank scrubber head and swapping it over.

Under the plug connector a new loom is fitted to the existing 02 sensor plugs. These come apart fairly easily and Uri’s replacement loom is marked for cell 1, 2 & 3 The plugs are re used on the end of the loom and the loom is connected to the jack plug by re usable non-crimping connectors. These allow removal of the loom so you can re wire the original configuration and send the unit up for servicing in a state that does not contravene CE mark. A smart move but it will be interesting to see Martins actual reaction to the jack plug through the head of the scrubber. Finally, the non-crimping connectors are taped up and the head is rebuilt. No easy task with the additional wiring but it all goes together somehow.


The black box locates on the bottom of the scrubber and is held in place with Velcro. The cables have plenty of slack for routing around the unit to the mouthpiece. The mounting I am using now works well but Uri is not happy with it so an improved unit is in the offing. The LED’s are paired red and green for each cell. Cell 1 is on the left. The unit is pre programmed to the user’s personal preference prior to installation. I stuck with Uri’s recommendations, as they appeared logical


Pp02 range Display signals
>1.6 Red constantly on
>=1.45 and <=1.6 Alternate red/green flash (slow flash)
>=1.15 and <=1.45 Green on constantly (high set point)
>=0.80 and <=1.15 Alternate green on/off (slow flash)
>=0.60 and <=0.8 Green on constantly with off flicker (low set point)
>=0.45 and <=0.6 Alternate red/green fast flash
>=0.05 and <=0.45 Alternate red on/off fast flash
<0.05 Both off

I used Velcro wraps to keep the cable tight against the breathing loop but only because he girls got upset when I nicked some of their hair bands. The final mounting bracket is work in progress but the temporary one supplied is held to the right of the mouthpiece so it does not interfere with shut downs and is held in place with a cable tie.


To set up the unit you simply switch on by plugging in a start switch into the charger plug. Then carry out the normal calibration cycle on the Inspiration. As the handsets switch from FLUSHING to CALIBRATING, you touch a contact button on the side of the HUD black box. The LEDs flash confirmation and the unit is good to go. Very simple but does require you to have the back off the unit so a minor faf on the boat pre dive.

The unit has a 48-hour duration rechargeable battery built in and a reusable-potting compound. This is apparently good for 1000 charges so should last a while. Each unit is pot tested prior to delivery. If one thing lets the professional look of the unit down, it’s the battery charger cable. This terminated in a piece of dowel with a pos and neg contact in each end and it looks pretty DIY. Due to restrictions on selling things with plugs on the battery charger is not supplied, however full specification is provided for suitable chargers.

In use, I found the display to be excellent. The response time is quicker than the Inspiration handsets and even on an ascent from 6m on a 0.7 set point it was quick to flash red indicating the dropping PP02. The unit emits a slow flashing green on low set point, which reminds the diver to switch to high set point. Once there a solid green is visible and it should stay that way throughout the dive. S the unit is failsafe and linked to all three 02 sensors it is usable as a primary display. Theoretically, no need to look at the hand sets at all throughout the dive. I used several reality checks to make sure it was functioning correctly and used dill flush to simulate failures ant it worked perfectly. Used in idiot mode you just see ANY red and check your handsets but with a full understanding of the various light signals, you can actually assess the problem just using the HUD.

Two other potential inspiration divers had a try dive on my unit on Saturday and after me reminding them several times to check their hand sets they both agreed that the HUD was a must have tool.

Finally, I ordered the VR3 link for the unit. This runs off cell 1 and does not provide forth cell backup. The Y piece and VR3 cable are now redundant and up for sale. I decided this system was neater then the forth cell and that reel time deco based on the actual solenoid activating cells would be beneficial. The extra cable and port added £80.00 to the bill but the sale of the forth cell holder and cable should cover that.

There is also an option of a separate display or ‘buddy display’. This is back mounted so your buddy can check your PP02 throughout the dive. Frankly if I am not responding to the flashing red lights in my face I am unconscious and I think my buddy would notice that, but it shows that the system is well thought through and holistic in design.

For further information, contact Uri via his web site. http://www.underwaterexperiences.com/rb_guardian.html

Uri is a very keen inspiration diver and more than willing to discuss your needs.

ATB
Mark Chase




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