Mike Ward
04-01-2013, 04:40 PM
This is a long post, sorry, but since actual sightings of the Poseidon seem to be rare you might find it interesting.
I bought my Poseidon because I fancied CCR, tried various units and liked this one best. Pure personal preference. It felt light on my back, was nice to breathe, weighs less than 10kg stripped for packing and I can pick it up one-handed ready to dive.
I knew it was a ‘recreational’ unit before I tried it and I wouldn’t have bothered except the guy I bought it from is both a good friend and a Poseidon dealer and assured me a full tech upgrade was on the way. It was still a leap of faith, and there was a degree of relief when Poseidon announced the tech unit and also confirmed that the price of my unit plus upgrade would be the same as buying the tech unit outright.
The standard unit comes with aluminium cylinders, but I specified mine with steel. The idea was to keep additional weight required to a minimum, and in the end I use less weight than I would with a single steel cylinder OC.
No wing is included, so I used my old DiveRite TransPac and attached the rebreather using a pair of cambands, a solution that is low-tech, low-profile, lightweight and works.
There didn't seem to be very many bits in the box when it arrived, they went together easily and the unit fired up nicely. t'internet has it that the Poseidon electronics are temperamental and will fail the automated pre-dive checks just to spite you. Not my experience so far. The only pre-start fails I've had were my fault. You can’t blame the unit if some dimwit pinches an O-ring.....
If the startup routine does fail the unit displays a code number to tell you which test failed and why - it runs something like forty tests, some of which can fail for more than one reason - then turns off. Poseidon provides a list of codes in the manual so you know what the issue was and can rectify it.
If you don't bother turning it on properly and just jump in Poseidon say the unit will hard-start and do the best it can, all the while merrily bleeping, buzzing and vibrating until you get out of the water. Haven't tried it and don't intend to.
The unit is powered by a rechargeable battery which sits at the top of the unit behind your head. It contains the master computer and is rated for 30 hours continuous operation. I found the handset display showed well over half capacity remaining after two days liveaboard diving, say 8 hrs in the water. Insert the battery in the charging station and it measures remaining charge and total battery capacity. Normally the battery simply charges up, taking an hour or two, but if the unit hasn't been used for some time or if the charger detects reduced total capacity it prompts a 'learn cycle', a complete discharge/recharge routine taking about 8 hours to complete. Poseidon say the battery will last for thousands of charging cycles.
The handset is on the end of a cable that I think is too long, but I'm only five foot seven so that might be me. I made a very snazzy (!) wrist-mount from some plastic pipe, cable-ties and bungee cord because I got fed up of continually clipping and unclipping the display so I could read it. At least I could read it, the numbers are nice and big and show the information very clearly. The downside of this, of course, is that the handset is on the big side. All in all, not my favourite bit of the unit.
The handset backlight comes on automatically when light levels drop, which means inside wrecks or even at the bottom of Stoney on a dull day as well as at night.
One oddity is that the dil and oxygen cylinder pressures are shown as a percentage of their full capacity rather than in bar, but in practice that doesn’t actually matter.
There's a red HUD which flashes red once every two minutes to prompt you to check the handset. It's reasonably visible, dependant on mask choice. Use a black-skirted mask and it's out of sight. Whenever the HUD flashes, a light also flashes in the unit battery behind your head to alert your buddy and the world at large.
If the unit detects a problem the HUD flashes continually and a buzzer sounds to tell you to take appropriate action. If the problem relates to ppO2 the mouthpiece will also vibrate. If that happens, you go OC by turning the lever on the standard fitment BOV. That's a one-finger job and the BOV breathes well in OC mode. The BOV is plumbed to the dil cylinder as supplied, so your next task will be to switch to the bail-out tin you're carrying, end the dive and ascend. That's the standard, trained response to all unit problems. Don't try to fix it, go OC and end the dive.
There is no manual oxygen add, and no way to manually add diluent except exhaling through the nose and triggering the ADV.
On descent the standard ADV works positively. Inhale and there's a slight resistance before the ADV opens and the gas addition seems steady.
The stock recreational unit is sold as air dil, but that actually means the diluent has to contain 21% oxygen. This is measured automatically in the pre-dive test routine and if it isn't 21% the unit won't start. I've been told it should tolerate up to 23%, but when I was given an ‘air’ dil cylinder actually containing 26% it refused to fire up…..
Loop ppO2 is monitored by two sensors. The output of both is checked as part of the automated pre-dive test sequence using dil and oxygen so you know the sensors are linear from ppO2 dil to 1bar. Then the primary oxygen sensor is tested automatically with O2 only as you drop below 6m, so you now know this sensor is linear to just over 1.6bar. By the time you’re at 12m the deep setpoint will have been achieved, controlled by the primary sensor, and by comparing the output of the primary and secondary sensors the unit assures itself and you that you have two sensors that are linear to the deep setpoint. After that the unit checks the primary sensor every couple of minutes with dil to make sure it’s reading correctly for the depth and also checks to make sure that both sensors are reading the same. Differences between the sensors or unexpected responses trigger alarms and you abort.
The volumes of gas used in the checking process are tiny and don't noticeably alter loop volume or ppO2.
Diving the unit you hear a regular 'shh-shh, shh-shh, shh-shh' behind your head, which is the solenoids injecting gas for calibration. In reality the sound was both a reassurance the unit was operating correctly and a better prompt to check the handset than the HUD, which I find hard to see in daylight.
Although the basic unit is recreational and intended for no-deco use only it still has a fully functional decompression computer as standard. This monitors remaining no decompression time very clearly to make sure you don't accidentally end up requiring mandatory stops. With five minutes NDT remaining a continuous flashing up-arrow (Like that on many dive computers) appears on the handset display, the HUD flashes once and the buzzer buzzes for approximately half a second. The idea is to prompt an ascent to allow the no-decompression time to flood back. Ignore the prompts and the flash and buzz are repeated every minute. If you accidentally go deeper than 40m you get a similar prompt to ascend.
If you miss the warnings and accidently slip into deco the HUD will flash regularly but the buzzer still only buzzes for half a second every minute. The unit itself continues to maintain set-point and the handset displays your current ascent ceiling and a total time to surface. Decompression algorithm is DCAP, which I can't find as a stand-alone piece of software but which seems pretty close in overall run-time to MV planner using 30/85 gradient factors, though with a very different profile.
The light built into the battery means the rest of the world can see that you’ve rather carelessly gone too deep or slipped into deco.
Surface setpoint can be adjusted to 0.4 or 0.5 bar ppO2, and deep setpoint between 1.0 and 1.3. The transition seems effectively linear with depth once you're a few metres deep on both descent and ascent. Higher ppO2 is not maintained through the shallow stops if you do accidently enter mandatory deco, but never drops below 0.9 bar until your mandatory stops are completed. A normoxic trimix battery is available that allows use of a minimum of 16% O2 and any helium fraction. This has no deco alarm, certification is to 48m and does maintain deep setpoint until mandatory deco ends.
In-water trim is nice, the valves-up configuration must help with this.
Daily strip-down, rinse, dry and re- build is straightforward, though pulling the end off the scrubber can to get to the sofnolime isn't easy. Plenty of O-ring grease helps, and there's a webbing strap to grab, but I found a rocking motion on each of the four lugs for the bolts that hold the can shut worked better. There are two sealing o-rings and once the first is clear the second comes out easily.
The unit is designed to use pre-packed scrubber cartridges. These are easy to use but more than twice the price of loose lime and I wasn't sure of getting them abroad so I bought a Tecme refillable cartridge. This has quite coarse metal mesh either end of the scrubber can so I dismantled a pre-packed scrubbed, removed the thin scrim from each and used these in the Tecme unit to avoid dust getting where it wasn't wanted.
Scrubber duration is officially 3 hours in 4 degree water. Poseidon recommends filling the oxygen cylinder to 130 bar so at ‘average usage’ the oxygen will last as long as the scrubber and you change both at the same time. Filling O2 to 200 bar didn't seem to cause any issues, but the display shows the O2 cylinder as 'full' unitl the pressure drops below 130 bar. Odd until you get used to it.
First stages have a standard DIN thread on the dil and the M26 on the oxygen, so I needed an adapter and then used standard 3l Inspo tanks abroad, and I carry the adapter just in case in the UK. I'll swap that out, probably.
I've had one leak, caused by the mouthpiece cable-tie coming loose. I couldn't believe the amount of water something so trivial allowed into the unit, the scrubber can was half-full.
It's an easy unit to dive and I'm very happy with mine. It’s nine months old, got 50 hours on it, split between the UK and the Red Sea, and still looks like new, give or take the odd scratch on the face of the display.
I bought my Poseidon because I fancied CCR, tried various units and liked this one best. Pure personal preference. It felt light on my back, was nice to breathe, weighs less than 10kg stripped for packing and I can pick it up one-handed ready to dive.
I knew it was a ‘recreational’ unit before I tried it and I wouldn’t have bothered except the guy I bought it from is both a good friend and a Poseidon dealer and assured me a full tech upgrade was on the way. It was still a leap of faith, and there was a degree of relief when Poseidon announced the tech unit and also confirmed that the price of my unit plus upgrade would be the same as buying the tech unit outright.
The standard unit comes with aluminium cylinders, but I specified mine with steel. The idea was to keep additional weight required to a minimum, and in the end I use less weight than I would with a single steel cylinder OC.
No wing is included, so I used my old DiveRite TransPac and attached the rebreather using a pair of cambands, a solution that is low-tech, low-profile, lightweight and works.
There didn't seem to be very many bits in the box when it arrived, they went together easily and the unit fired up nicely. t'internet has it that the Poseidon electronics are temperamental and will fail the automated pre-dive checks just to spite you. Not my experience so far. The only pre-start fails I've had were my fault. You can’t blame the unit if some dimwit pinches an O-ring.....
If the startup routine does fail the unit displays a code number to tell you which test failed and why - it runs something like forty tests, some of which can fail for more than one reason - then turns off. Poseidon provides a list of codes in the manual so you know what the issue was and can rectify it.
If you don't bother turning it on properly and just jump in Poseidon say the unit will hard-start and do the best it can, all the while merrily bleeping, buzzing and vibrating until you get out of the water. Haven't tried it and don't intend to.
The unit is powered by a rechargeable battery which sits at the top of the unit behind your head. It contains the master computer and is rated for 30 hours continuous operation. I found the handset display showed well over half capacity remaining after two days liveaboard diving, say 8 hrs in the water. Insert the battery in the charging station and it measures remaining charge and total battery capacity. Normally the battery simply charges up, taking an hour or two, but if the unit hasn't been used for some time or if the charger detects reduced total capacity it prompts a 'learn cycle', a complete discharge/recharge routine taking about 8 hours to complete. Poseidon say the battery will last for thousands of charging cycles.
The handset is on the end of a cable that I think is too long, but I'm only five foot seven so that might be me. I made a very snazzy (!) wrist-mount from some plastic pipe, cable-ties and bungee cord because I got fed up of continually clipping and unclipping the display so I could read it. At least I could read it, the numbers are nice and big and show the information very clearly. The downside of this, of course, is that the handset is on the big side. All in all, not my favourite bit of the unit.
The handset backlight comes on automatically when light levels drop, which means inside wrecks or even at the bottom of Stoney on a dull day as well as at night.
One oddity is that the dil and oxygen cylinder pressures are shown as a percentage of their full capacity rather than in bar, but in practice that doesn’t actually matter.
There's a red HUD which flashes red once every two minutes to prompt you to check the handset. It's reasonably visible, dependant on mask choice. Use a black-skirted mask and it's out of sight. Whenever the HUD flashes, a light also flashes in the unit battery behind your head to alert your buddy and the world at large.
If the unit detects a problem the HUD flashes continually and a buzzer sounds to tell you to take appropriate action. If the problem relates to ppO2 the mouthpiece will also vibrate. If that happens, you go OC by turning the lever on the standard fitment BOV. That's a one-finger job and the BOV breathes well in OC mode. The BOV is plumbed to the dil cylinder as supplied, so your next task will be to switch to the bail-out tin you're carrying, end the dive and ascend. That's the standard, trained response to all unit problems. Don't try to fix it, go OC and end the dive.
There is no manual oxygen add, and no way to manually add diluent except exhaling through the nose and triggering the ADV.
On descent the standard ADV works positively. Inhale and there's a slight resistance before the ADV opens and the gas addition seems steady.
The stock recreational unit is sold as air dil, but that actually means the diluent has to contain 21% oxygen. This is measured automatically in the pre-dive test routine and if it isn't 21% the unit won't start. I've been told it should tolerate up to 23%, but when I was given an ‘air’ dil cylinder actually containing 26% it refused to fire up…..
Loop ppO2 is monitored by two sensors. The output of both is checked as part of the automated pre-dive test sequence using dil and oxygen so you know the sensors are linear from ppO2 dil to 1bar. Then the primary oxygen sensor is tested automatically with O2 only as you drop below 6m, so you now know this sensor is linear to just over 1.6bar. By the time you’re at 12m the deep setpoint will have been achieved, controlled by the primary sensor, and by comparing the output of the primary and secondary sensors the unit assures itself and you that you have two sensors that are linear to the deep setpoint. After that the unit checks the primary sensor every couple of minutes with dil to make sure it’s reading correctly for the depth and also checks to make sure that both sensors are reading the same. Differences between the sensors or unexpected responses trigger alarms and you abort.
The volumes of gas used in the checking process are tiny and don't noticeably alter loop volume or ppO2.
Diving the unit you hear a regular 'shh-shh, shh-shh, shh-shh' behind your head, which is the solenoids injecting gas for calibration. In reality the sound was both a reassurance the unit was operating correctly and a better prompt to check the handset than the HUD, which I find hard to see in daylight.
Although the basic unit is recreational and intended for no-deco use only it still has a fully functional decompression computer as standard. This monitors remaining no decompression time very clearly to make sure you don't accidentally end up requiring mandatory stops. With five minutes NDT remaining a continuous flashing up-arrow (Like that on many dive computers) appears on the handset display, the HUD flashes once and the buzzer buzzes for approximately half a second. The idea is to prompt an ascent to allow the no-decompression time to flood back. Ignore the prompts and the flash and buzz are repeated every minute. If you accidentally go deeper than 40m you get a similar prompt to ascend.
If you miss the warnings and accidently slip into deco the HUD will flash regularly but the buzzer still only buzzes for half a second every minute. The unit itself continues to maintain set-point and the handset displays your current ascent ceiling and a total time to surface. Decompression algorithm is DCAP, which I can't find as a stand-alone piece of software but which seems pretty close in overall run-time to MV planner using 30/85 gradient factors, though with a very different profile.
The light built into the battery means the rest of the world can see that you’ve rather carelessly gone too deep or slipped into deco.
Surface setpoint can be adjusted to 0.4 or 0.5 bar ppO2, and deep setpoint between 1.0 and 1.3. The transition seems effectively linear with depth once you're a few metres deep on both descent and ascent. Higher ppO2 is not maintained through the shallow stops if you do accidently enter mandatory deco, but never drops below 0.9 bar until your mandatory stops are completed. A normoxic trimix battery is available that allows use of a minimum of 16% O2 and any helium fraction. This has no deco alarm, certification is to 48m and does maintain deep setpoint until mandatory deco ends.
In-water trim is nice, the valves-up configuration must help with this.
Daily strip-down, rinse, dry and re- build is straightforward, though pulling the end off the scrubber can to get to the sofnolime isn't easy. Plenty of O-ring grease helps, and there's a webbing strap to grab, but I found a rocking motion on each of the four lugs for the bolts that hold the can shut worked better. There are two sealing o-rings and once the first is clear the second comes out easily.
The unit is designed to use pre-packed scrubber cartridges. These are easy to use but more than twice the price of loose lime and I wasn't sure of getting them abroad so I bought a Tecme refillable cartridge. This has quite coarse metal mesh either end of the scrubber can so I dismantled a pre-packed scrubbed, removed the thin scrim from each and used these in the Tecme unit to avoid dust getting where it wasn't wanted.
Scrubber duration is officially 3 hours in 4 degree water. Poseidon recommends filling the oxygen cylinder to 130 bar so at ‘average usage’ the oxygen will last as long as the scrubber and you change both at the same time. Filling O2 to 200 bar didn't seem to cause any issues, but the display shows the O2 cylinder as 'full' unitl the pressure drops below 130 bar. Odd until you get used to it.
First stages have a standard DIN thread on the dil and the M26 on the oxygen, so I needed an adapter and then used standard 3l Inspo tanks abroad, and I carry the adapter just in case in the UK. I'll swap that out, probably.
I've had one leak, caused by the mouthpiece cable-tie coming loose. I couldn't believe the amount of water something so trivial allowed into the unit, the scrubber can was half-full.
It's an easy unit to dive and I'm very happy with mine. It’s nine months old, got 50 hours on it, split between the UK and the Red Sea, and still looks like new, give or take the odd scratch on the face of the display.