Po2 reading low

colinicky · 2nd September 2006, 22:41

Having dived my vision since January I am slowly getting used to it .Up untill now when I have calibrated the unit then gone on to prebreathe the unit the po2 has sat at .70 on all 3 cells ,when I have dived the unit it has read a solid 1.3 on the high set point .
But on Thursday night I put the unit together as normal but on the prebreathe the display read .65 to .66 on all 3 cells .Repeated the procedure including full calibration but still the same readings .repeated this on Friday morning before loading on the boat & also prior to the actual dive ,still the same on reaching the bottom of the shot on high set point the displaed po2 never went above 1.27 on all 3 cells

.I did not notice any excessive injection frequency or duration during the dive . If I manually injected O2 then I could raise the displayed po2 .This was repeated on dive 2 as well .
Anybody else experienced this or have an answer for it ?

decoweenie · 3rd September 2006, 08:24

Just some quick questions came to mind...

Did you verify the input set-points on the handset are correct (i.e. 0.7 and 1.3) and were not changed unintentionally ?

Did you do a diluent flush to check the cells while on bottom ?

colinicky · 3rd September 2006, 08:49

yes set points are correct & yes did dil flush @30m with air dil equalled a reading of .83 so .01 of target .the 30m was sat on a piece of wreck so no chance of movement while doing the flush

decoweenie · 3rd September 2006, 09:02

... then I have no idea...

Sorry!

UKSteve · 3rd September 2006, 10:08

Hi,

Have you recently changed the software version? Wondering if the latest software version handles rounding differently. i.e. it says ..1.27? that is 1.3 at 1 and a bit decimal places so no need to fire the solenoid?

I could see why they might do this to prevent spiking over the desired set point

EDIT... in fact this is what was said in the release notes for version 02_01_02

• The solenoid progressive activity band has been enlarged from 0.05 bar to 0.1 bar below setpoint. E.g, if you are using a setpoint of 1.3, if the PO2 in the loop is above 1.3 bar the solenoid doesn’t open, below 1.20 bar the solenoid is open continuously, between 1,20 and 1.30 bar the oxygen addition is progressive – the closer you are to setpoint the shorter the opening time. This alteration decreases the chance of overshoot after the constant solenoid open periods.
Steve

colinicky · 3rd September 2006, 12:45

Thanks Steve
I hate people who actually read the instructions

Doh
I will run it past Nicky tomorrow to check but could explain it

decoweenie · 3rd September 2006, 12:48

Quote: (Originally Posted by colinicky)

Thanks Steve

Ditto.

I haven't bothered to update the software so didn't read what changes have been added...

2nd September 2006, 22:41	#1 (permalink)
colinicky RBW Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Mar 2005 Location: uk Posts: 678	Po2 reading low Having dived my vision since January I am slowly getting used to it .Up untill now when I have calibrated the unit then gone on to prebreathe the unit the po2 has sat at .70 on all 3 cells ,when I have dived the unit it has read a solid 1.3 on the high set point . But on Thursday night I put the unit together as normal but on the prebreathe the display read .65 to .66 on all 3 cells .Repeated the procedure including full calibration but still the same readings .repeated this on Friday morning before loading on the boat & also prior to the actual dive ,still the same on reaching the bottom of the shot on high set point the displaed po2 never went above 1.27 on all 3 cells .I did not notice any excessive injection frequency or duration during the dive . If I manually injected O2 then I could raise the displayed po2 .This was repeated on dive 2 as well . Anybody else experienced this or have an answer for it ? __________________ Colin I trust my rebreather completely , I just don't trust the user onwards & downwards
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3rd September 2006, 08:24	#2 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Po2 reading low Just some quick questions came to mind... Did you verify the input set-points on the handset are correct (i.e. 0.7 and 1.3) and were not changed unintentionally ? Did you do a diluent flush to check the cells while on bottom ? __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
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3rd September 2006, 08:49	#3 (permalink)
colinicky RBW Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Mar 2005 Location: uk Posts: 678	Re: Po2 reading low yes set points are correct & yes did dil flush @30m with air dil equalled a reading of .83 so .01 of target .the 30m was sat on a piece of wreck so no chance of movement while doing the flush __________________ Colin I trust my rebreather completely , I just don't trust the user onwards & downwards
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3rd September 2006, 09:02	#4 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Po2 reading low ... then I have no idea... Sorry! __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
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3rd September 2006, 10:08	#5 (permalink)
UKSteve Steve Collard Current Rebreather/s: Inspiration Vision Other Rebreather/s: Join Date: Jul 2005 Location: Weymouth, UK Posts: 600	Re: Po2 reading low Hi, Have you recently changed the software version? Wondering if the latest software version handles rounding differently. i.e. it says ..1.27? that is 1.3 at 1 and a bit decimal places so no need to fire the solenoid? I could see why they might do this to prevent spiking over the desired set point EDIT... in fact this is what was said in the release notes for version 02_01_02 • The solenoid progressive activity band has been enlarged from 0.05 bar to 0.1 bar below setpoint. E.g, if you are using a setpoint of 1.3, if the PO2 in the loop is above 1.3 bar the solenoid doesn’t open, below 1.20 bar the solenoid is open continuously, between 1,20 and 1.30 bar the oxygen addition is progressive – the closer you are to setpoint the shorter the opening time. This alteration decreases the chance of overshoot after the constant solenoid open periods. Steve Last edited by UKSteve : 3rd September 2006 at 10:15.
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3rd September 2006, 12:45	#6 (permalink)
colinicky RBW Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Mar 2005 Location: uk Posts: 678	Re: Po2 reading low Thanks Steve I hate people who actually read the instructions Doh I will run it past Nicky tomorrow to check but could explain it __________________ Colin I trust my rebreather completely , I just don't trust the user onwards & downwards
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3rd September 2006, 12:48	#7 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,487	Re: Po2 reading low Quote: (Originally Posted by colinicky) Thanks Steve Ditto. I haven't bothered to update the software so didn't read what changes have been added... __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM
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