Turning 4th cell OFF in a 2pin VR£ - impossible??!

Mark Chase · 27th June 2006, 17:16

I reckon disconnecting a VR3 thats reading a high PP02 and giving you crap deco info is worthwhile for the risk and the one off cleaning exercise. Its happened to me when my VR3 showed a PP02 of 2. something but was not in agreement with my hand sets and once when the cable fell out.

However...

Your being totally paranoid if the VR3 is showing a good cell reading, then its giving you good deco info. If you want to be safe then manually extend the deco with slow ascents and increased shallow hang times, you don't HAVE to go up or get out just because it says so.

I just don't see an issue as I know your more than capable of figuring out how to pad it out in your head.

I cant see reconnecting the cable working. Salt water is an excellent conductor and moisture in the connection must surely short out across the pins. Taking it out and leaving it out is fine but putting it in during a dive must be asking for trouble.

Packing the connector with silicone is a bad idea as silicone is an excellent insulator and could cause contact failure even with a very thin membrane with such low voltage.

ATB

Mark Chase

Dinspiration · 27th June 2006, 18:02

Hello

VR2 & VR3 with the old 2.1 firmware allow you just to disable the external cell reading. VR2 and VR3 with firmware 3.x or higher allow you to disable the external cell (Xfunc) and/or external decompression calculation (XDec).

XFunc set to Xo2 = external cell reading activated
XDec set to off = Cell reading is NOT used for decompression calculation

XFunc set to off = external cell reading disabled

XFunc set to Xo2 = external cell reading activated
XDec set to On = Cell reading is used for decompression calculation

If Xdec is set to off or on older versions the cell is deactivated the computer will not use any information from the 4th cell to calculate decompression

CCR Mode: If the PO2 of your diluent at the depth is higher than your actual setpoint, the VR computer will show and calculate the actual PO2. There is no info coming from the 4th cell at all. Example: Diluent = Air, Your depth = 60 Meter, set point 1.3, P02 = 1.47 bar. Even with a diluent flush you PO2 will not be lowwer than 1.47!

DINspiration

Mark Chase · 27th June 2006, 20:30

Quote: (Originally Posted by Dinspiration)

CCR Mode: If the PO2 of your diluent at the depth is higher than your actual setpoint, the VR computer will show and calculate the actual PO2. There is no info coming from the 4th cell at all. Example: Diluent = Air, Your depth = 60 Meter, set point 1.3, P02 = 1.47 bar. Even with a diluent flush you PO2 will not be lowwer than 1.47!

DINspiration

I remember this now you mention it and I remember thinking what an utterly stupid idea.

Don't they understand how a CCR works? I could dive an air diluent at 100m and still be on 1.3 for the whole dive. The unit wont inject until I have depleted the 02 reserves in the counter lung and after that it will keep it at 1.3 whilst the stupid VR3 is calculating deco on 2.31????

OK doing this is stupid but there have been occasions where the dive has been changed and ended up slightly deeper than my diluent is ideal for. I have to admit to have been on a 1.4 diluent running 1.3 on the unit. I also have to admit to a rather dodgy 65m air diluient dive in the Red sea.

Mr Gurr wasent thinking streight when he came up with that idea.

ATB

Mark Chase

Mdemon · 27th June 2006, 21:21

Quote: (Originally Posted by Mark Chase)

Your being totally paranoid if the VR3 is showing a good cell reading, then its giving you good deco info. If you want to be safe then manually extend the deco with slow ascents and increased shallow hang times, you don't HAVE to go up or get out just because it says so.

I just don't see an issue as I know your more than capable of figuring out how to pad it out in your head.

I cant see reconnecting the cable working. Salt water is an excellent conductor and moisture in the connection must surely short out across the pins. Taking it out and leaving it out is fine but putting it in during a dive must be asking for trouble.

The more I think about it, the more I think you are correct. The 4th cell reads lower, so conservative. What it won't allow me to do is push up the setpoint as conservatism. Mucking about connecting cables sounds like a recipe for disaster, greased up or not! Thanks all.

Barrie Law · 27th June 2006, 21:41

Quote: (Originally Posted by Mark Chase)

I remember this now you mention it and I remember thinking what an utterly stupid idea.

Don't they understand how a CCR works? I could dive an air diluent at 100m and still be on 1.3 for the whole dive. The unit wont inject until I have depleted the 02 reserves in the counter lung and after that it will keep it at 1.3 whilst the stupid VR3 is calculating deco on 2.31????

OK doing this is stupid but there have been occasions where the dive has been changed and ended up slightly deeper than my diluent is ideal for. I have to admit to have been on a 1.4 diluent running 1.3 on the unit. I also have to admit to a rather dodgy 65m air diluient dive in the Red sea.

Mr Gurr wasent thinking streight when he came up with that idea.

ATB

Mark Chase

Hi Mark,
You are assuming you can breath down the PPO2 of your Diluent to a point below your unit setpoint ie 1.3 (air at 100mtrs = 2.31 PO2) this is not correct.
The PPO2 of the diluent gas can be altered very slightly by reducing the loop volume but it is fractional, the ADV will kick in and restore the PPO2.
If you isolate the ADV and use the manual diluent injection you will find the counter lungs bottoming out before you see a significant drop in the PPO2.

In short you cannot breath down the PPO2 of a diluent gas.

Regards

Barrie Law · 27th June 2006, 21:50

Quote: (Originally Posted by Mdemon)

The more I think about it, the more I think you are correct. The 4th cell reads lower, so conservative. What it won't allow me to do is push up the setpoint as conservatism. Mucking about connecting cables sounds like a recipe for disaster, greased up or not! Thanks all.

Hi John,
The connectors on the Vr3 will not be effected by Salt water and the caps are Dust protectors only, you would have to clean the connectors regularly with white vinegar to prevent corrosion building up.

Regards

Mark Chase · 27th June 2006, 22:03

Quote: (Originally Posted by Barrie Law)

Hi Mark,
You are assuming you can breath down the PPO2 of your Diluent to a point below your unit setpoint ie 1.3 (air at 100mtrs = 2.31 PO2) this is not correct.
The PPO2 of the diluent gas can be altered very slightly by reducing the loop volume but it is fractional, the ADV will kick in and restore the PPO2.
If you isolate the ADV and use the manual diluent injection you will find the counter lungs bottoming out before you see a significant drop in the PPO2.

In short you cannot breath down the PPO2 of a diluent gas.

Regards

?? I find this very odd as my ADV never fires during the bottom section of a dive unless I want it to. And yet my solenoid fires every 6 seconds to inject 02??

The KISS units constantly inject 02? which you then metabolize?

I often here it said that the 3ltr 02 bottle on a Insp can last for 10 hours. Well thats 60ltrs per hour of 02 your using up @ 1lpm. Seeing as counter lungs are only 5 -8ltrs and you only have 21% of that as 02 thats about 1ltr of 02 in the lungs max at any time. So shouldn't it take about 1min to reduce that to 0? and you dint have to reduce it to 0 you only have to get it down to 1.3? so you might have a 10% reduction in counter lung capacity during that period.

However you work the maths I can say for sure I did a 65m dive on 1.3 set point on air which should have given me 1.55 loads of flashing lights and the ocasional buzzer. That just didnt hapen i just sat on a 1.3 set point.

ATB

Mark Chase

Mdemon · 27th June 2006, 22:28

Actually, I've done similar and also didn't get high PO2 warnings.

Barrie Law · 27th June 2006, 23:07

Quote: (Originally Posted by Mark Chase)

?? I find this very odd as my ADV never fires during the bottom section of a dive unless I want it to. And yet my solenoid fires every 6 seconds to inject 02??

The KISS units constantly inject 02? which you then metabolize?

I often here it said that the 3ltr 02 bottle on a Insp can last for 10 hours. Well thats 60ltrs per hour of 02 your using up @ 1lpm. Seeing as counter lungs are only 5 -8ltrs and you only have 21% of that as 02 thats about 1ltr of 02 in the lungs max at any time. So shouldn't it take about 1min to reduce that to 0? and you dint have to reduce it to 0 you only have to get it down to 1.3? so you might have a 10% reduction in counter lung capacity during that period.

However you work the maths I can say for sure I did a 65m dive on 1.3 set point on air which should have given me 1.55 loads of flashing lights and the ocasional buzzer. That just didnt hapen i just sat on a 1.3 set point.

ATB

Mark Chase

Mark,
I am not disputing you are metabolising the oxygen and that it will be replaced by the solenoid depending on your metabolism, the ADV would not normally kick in when the diluent is correct for the depth ie 1.3 PPO2.
The remainder of the Partial Pressure is the inert gas in the diluent eg Nitrogen or Helium the only variable is the loop volume that is to say, if you inject diluent to over pressure and then breath it down the PPO2 can be dropped but not in a significant way.

If you breath down the loop on the surface with the oxygen switched off you will notice the loop deflating and the ADV kicking in or if no diluent is added the counter lungs will collapse further until the loop becomes hypoxic.

This is because the loop has a PPn2 of .79% (air Dil) and when you remove some or all of the Oxygen you still have a PPn2 of .79% but you have reduced the loop size not increased the PPn2 to 100%, think of someone putting a plastic bag over their head it will shrink as they metabolise the oxygen and they suffocate.

Regards

Mdemon · 28th June 2006, 06:37

Quote: (Originally Posted by Barrie Law)

This is because the loop has a PPn2 of .79% (air Dil) and when you remove some or all of the Oxygen you still have a PPn2 of .79% but you have reduced the loop size not increased the PPn2 to 100%, think of someone putting a plastic bag over their head it will shrink as they metabolise the oxygen and they suffocate.

Run this one by me again Barrie? If I have a 50li bin liner on my head, and I sit there puffing away until all the O2 is used, there will still be lots of gas in the bag, with a tiny fraction of O2 and a fair chunk of CO2. There's lots of gas, so no ADV-activating sub-ambient pressures...

Our toys scrub the CO2, so in this example, we'd have a big bag of nitrogen with a hint of O2. Swap the N2 for He and you have an explanation for how you can dive hot dils without constant beeping...

27th June 2006, 17:16	#11 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,556	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! I reckon disconnecting a VR3 thats reading a high PP02 and giving you crap deco info is worthwhile for the risk and the one off cleaning exercise. Its happened to me when my VR3 showed a PP02 of 2. something but was not in agreement with my hand sets and once when the cable fell out. However... Your being totally paranoid if the VR3 is showing a good cell reading, then its giving you good deco info. If you want to be safe then manually extend the deco with slow ascents and increased shallow hang times, you don't HAVE to go up or get out just because it says so. I just don't see an issue as I know your more than capable of figuring out how to pad it out in your head. I cant see reconnecting the cable working. Salt water is an excellent conductor and moisture in the connection must surely short out across the pins. Taking it out and leaving it out is fine but putting it in during a dive must be asking for trouble. Packing the connector with silicone is a bad idea as silicone is an excellent insulator and could cause contact failure even with a very thin membrane with such low voltage. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
(Offline)

27th June 2006, 18:02	#12 (permalink)
Dinspiration Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Other CCR Join Date: Dec 2005 Location: Switzerland Posts: 208	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! Hello VR2 & VR3 with the old 2.1 firmware allow you just to disable the external cell reading. VR2 and VR3 with firmware 3.x or higher allow you to disable the external cell (Xfunc) and/or external decompression calculation (XDec). XFunc set to Xo2 = external cell reading activated XDec set to off = Cell reading is NOT used for decompression calculation XFunc set to off = external cell reading disabled XFunc set to Xo2 = external cell reading activated XDec set to On = Cell reading is used for decompression calculation If Xdec is set to off or on older versions the cell is deactivated the computer will not use any information from the 4th cell to calculate decompression CCR Mode: If the PO2 of your diluent at the depth is higher than your actual setpoint, the VR computer will show and calculate the actual PO2. There is no info coming from the 4th cell at all. Example: Diluent = Air, Your depth = 60 Meter, set point 1.3, P02 = 1.47 bar. Even with a diluent flush you PO2 will not be lowwer than 1.47! DINspiration
(Offline)

27th June 2006, 20:30	#13 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,556	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! Quote: (Originally Posted by Dinspiration) CCR Mode: If the PO2 of your diluent at the depth is higher than your actual setpoint, the VR computer will show and calculate the actual PO2. There is no info coming from the 4th cell at all. Example: Diluent = Air, Your depth = 60 Meter, set point 1.3, P02 = 1.47 bar. Even with a diluent flush you PO2 will not be lowwer than 1.47! DINspiration I remember this now you mention it and I remember thinking what an utterly stupid idea. Don't they understand how a CCR works? I could dive an air diluent at 100m and still be on 1.3 for the whole dive. The unit wont inject until I have depleted the 02 reserves in the counter lung and after that it will keep it at 1.3 whilst the stupid VR3 is calculating deco on 2.31???? OK doing this is stupid but there have been occasions where the dive has been changed and ended up slightly deeper than my diluent is ideal for. I have to admit to have been on a 1.4 diluent running 1.3 on the unit. I also have to admit to a rather dodgy 65m air diluient dive in the Red sea. Mr Gurr wasent thinking streight when he came up with that idea. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
(Offline)

27th June 2006, 21:21	#14 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,904	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! Quote: (Originally Posted by Mark Chase) Your being totally paranoid if the VR3 is showing a good cell reading, then its giving you good deco info. If you want to be safe then manually extend the deco with slow ascents and increased shallow hang times, you don't HAVE to go up or get out just because it says so. I just don't see an issue as I know your more than capable of figuring out how to pad it out in your head. I cant see reconnecting the cable working. Salt water is an excellent conductor and moisture in the connection must surely short out across the pins. Taking it out and leaving it out is fine but putting it in during a dive must be asking for trouble. The more I think about it, the more I think you are correct. The 4th cell reads lower, so conservative. What it won't allow me to do is push up the setpoint as conservatism. Mucking about connecting cables sounds like a recipe for disaster, greased up or not! Thanks all. __________________ www.southwestmafia.com "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"
(Offline)

27th June 2006, 21:41	#15 (permalink)
Barrie Law RebreatherWorld Sponsor Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Jun 2005 Location: Ireland Posts: 726	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! Quote: (Originally Posted by Mark Chase) I remember this now you mention it and I remember thinking what an utterly stupid idea. Don't they understand how a CCR works? I could dive an air diluent at 100m and still be on 1.3 for the whole dive. The unit wont inject until I have depleted the 02 reserves in the counter lung and after that it will keep it at 1.3 whilst the stupid VR3 is calculating deco on 2.31???? OK doing this is stupid but there have been occasions where the dive has been changed and ended up slightly deeper than my diluent is ideal for. I have to admit to have been on a 1.4 diluent running 1.3 on the unit. I also have to admit to a rather dodgy 65m air diluient dive in the Red sea. Mr Gurr wasent thinking streight when he came up with that idea. ATB Mark Chase Hi Mark, You are assuming you can breath down the PPO2 of your Diluent to a point below your unit setpoint ie 1.3 (air at 100mtrs = 2.31 PO2) this is not correct. The PPO2 of the diluent gas can be altered very slightly by reducing the loop volume but it is fractional, the ADV will kick in and restore the PPO2. If you isolate the ADV and use the manual diluent injection you will find the counter lungs bottoming out before you see a significant drop in the PPO2. In short you cannot breath down the PPO2 of a diluent gas. Regards __________________ Barrie Law Rebreather World Store Supplying the Rebreather World Tel:US +19548403892 Fax:US+19543333792 Tel:EU+442071930496 Fax:EU+442077606344 Mobile+353876880628 Skype:barrielaw Email: barrie@rebreatherworldstore.com
(Offline)

27th June 2006, 21:50	#16 (permalink)
Barrie Law RebreatherWorld Sponsor Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Jun 2005 Location: Ireland Posts: 726	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! Quote: (Originally Posted by Mdemon) The more I think about it, the more I think you are correct. The 4th cell reads lower, so conservative. What it won't allow me to do is push up the setpoint as conservatism. Mucking about connecting cables sounds like a recipe for disaster, greased up or not! Thanks all. Hi John, The connectors on the Vr3 will not be effected by Salt water and the caps are Dust protectors only, you would have to clean the connectors regularly with white vinegar to prevent corrosion building up. Regards __________________ Barrie Law Rebreather World Store Supplying the Rebreather World Tel:US +19548403892 Fax:US+19543333792 Tel:EU+442071930496 Fax:EU+442077606344 Mobile+353876880628 Skype:barrielaw Email: barrie@rebreatherworldstore.com
(Offline)

27th June 2006, 22:03	#17 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,556	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! Quote: (Originally Posted by Barrie Law) Hi Mark, You are assuming you can breath down the PPO2 of your Diluent to a point below your unit setpoint ie 1.3 (air at 100mtrs = 2.31 PO2) this is not correct. The PPO2 of the diluent gas can be altered very slightly by reducing the loop volume but it is fractional, the ADV will kick in and restore the PPO2. If you isolate the ADV and use the manual diluent injection you will find the counter lungs bottoming out before you see a significant drop in the PPO2. In short you cannot breath down the PPO2 of a diluent gas. Regards ?? I find this very odd as my ADV never fires during the bottom section of a dive unless I want it to. And yet my solenoid fires every 6 seconds to inject 02?? The KISS units constantly inject 02? which you then metabolize? I often here it said that the 3ltr 02 bottle on a Insp can last for 10 hours. Well thats 60ltrs per hour of 02 your using up @ 1lpm. Seeing as counter lungs are only 5 -8ltrs and you only have 21% of that as 02 thats about 1ltr of 02 in the lungs max at any time. So shouldn't it take about 1min to reduce that to 0? and you dint have to reduce it to 0 you only have to get it down to 1.3? so you might have a 10% reduction in counter lung capacity during that period. However you work the maths I can say for sure I did a 65m dive on 1.3 set point on air which should have given me 1.55 loads of flashing lights and the ocasional buzzer. That just didnt hapen i just sat on a 1.3 set point. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
(Offline)

27th June 2006, 22:28	#18 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,904	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! Actually, I've done similar and also didn't get high PO2 warnings. __________________ www.southwestmafia.com "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"
(Offline)

27th June 2006, 23:07	#19 (permalink)
Barrie Law RebreatherWorld Sponsor Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Jun 2005 Location: Ireland Posts: 726	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! Quote: (Originally Posted by Mark Chase) ?? I find this very odd as my ADV never fires during the bottom section of a dive unless I want it to. And yet my solenoid fires every 6 seconds to inject 02?? The KISS units constantly inject 02? which you then metabolize? I often here it said that the 3ltr 02 bottle on a Insp can last for 10 hours. Well thats 60ltrs per hour of 02 your using up @ 1lpm. Seeing as counter lungs are only 5 -8ltrs and you only have 21% of that as 02 thats about 1ltr of 02 in the lungs max at any time. So shouldn't it take about 1min to reduce that to 0? and you dint have to reduce it to 0 you only have to get it down to 1.3? so you might have a 10% reduction in counter lung capacity during that period. However you work the maths I can say for sure I did a 65m dive on 1.3 set point on air which should have given me 1.55 loads of flashing lights and the ocasional buzzer. That just didnt hapen i just sat on a 1.3 set point. ATB Mark Chase Mark, I am not disputing you are metabolising the oxygen and that it will be replaced by the solenoid depending on your metabolism, the ADV would not normally kick in when the diluent is correct for the depth ie 1.3 PPO2. The remainder of the Partial Pressure is the inert gas in the diluent eg Nitrogen or Helium the only variable is the loop volume that is to say, if you inject diluent to over pressure and then breath it down the PPO2 can be dropped but not in a significant way. If you breath down the loop on the surface with the oxygen switched off you will notice the loop deflating and the ADV kicking in or if no diluent is added the counter lungs will collapse further until the loop becomes hypoxic. This is because the loop has a PPn2 of .79% (air Dil) and when you remove some or all of the Oxygen you still have a PPn2 of .79% but you have reduced the loop size not increased the PPn2 to 100%, think of someone putting a plastic bag over their head it will shrink as they metabolise the oxygen and they suffocate. Regards __________________ Barrie Law Rebreather World Store Supplying the Rebreather World Tel:US +19548403892 Fax:US+19543333792 Tel:EU+442071930496 Fax:EU+442077606344 Mobile+353876880628 Skype:barrielaw Email: barrie@rebreatherworldstore.com
(Offline)

28th June 2006, 06:37	#20 (permalink)
Mdemon SiegeEngine II Current Rebreather/s: Inspiration Classic Home Build Other Rebreather/s: Inspiration Classic Home Build Join Date: Feb 2007 Location: SWUK Posts: 1,904	Re: Turning 4th cell OFF in a 2pin VR£ - impossible??! Quote: (Originally Posted by Barrie Law) This is because the loop has a PPn2 of .79% (air Dil) and when you remove some or all of the Oxygen you still have a PPn2 of .79% but you have reduced the loop size not increased the PPn2 to 100%, think of someone putting a plastic bag over their head it will shrink as they metabolise the oxygen and they suffocate. Run this one by me again Barrie? If I have a 50li bin liner on my head, and I sit there puffing away until all the O2 is used, there will still be lots of gas in the bag, with a tiny fraction of O2 and a fair chunk of CO2. There's lots of gas, so no ADV-activating sub-ambient pressures... Our toys scrub the CO2, so in this example, we'd have a big bag of nitrogen with a hint of O2. Swap the N2 for He and you have an explanation for how you can dive hot dils without constant beeping... __________________ www.southwestmafia.com "Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode