Calibration frequency requirements...

Underwaterbear · 22nd June 2006, 02:02

Quote:

It may not make sense, but at least with the classic when I try and check the cal after a few days its always been off by more than a few percent.. With the HH its almost always still been on, and in these cases I check the cells readings and if they changed by more than a few MV in oxygen, I'll keep a close eye on them for replacement (which is usually necessary)....

It's more than likely that the difference you are seeing over a few days is related to changes in atmospheric pressure which may fluctuate by up to 5% between highs and lows.

silent running · 22nd June 2006, 02:57

Quote: (Originally Posted by Underwaterbear)

It's more than likely that the difference you are seeing over a few days is related to changes in atmospheric pressure which may fluctuate by up to 5% between highs and lows.

Ahhh, never thought of this. Thanks, UB. I always assumed it was only necessary to cal day to day because of the cells slight decline, or not so slight decline, as the case maybe with a bad one. I do the electronic cal at the begining of every dive day, and if I get the same reading from the same batch of O2 on the analogue gage, I don't mess with it. Just got back from a trip, 40hrs of diving, adjusted the 2dry cal potts once at the begining, didn't have to mess with them again. -Andy

***jradomski*** · 22nd June 2006, 05:48

Quote: (Originally Posted by Underwaterbear)

It's more than likely that the difference you are seeing over a few days is related to changes in atmospheric pressure which may fluctuate by up to 5% between highs and lows.

not really.. If calibrated properly, all the sensors should remain consitent and a loop flush with oxygen should result in a reading off the atmospheric pressure multiplied by the oxygen percentage of the source..

I don't assume its going to read 1.01 (insp is in bar) every day, every where..

even if atmospheric pressure changes it shouldnt effect the calibration, since cells ARE a po2 device and are tied to pressure changes, if the person didnt calibrate correctly by putting in the correct surface pressure, then errors should be expected. The default 1000mb on the inspiration is not accurate for many locals.. Its not even the standard accepted atmosphere ( 1013 mb)

Underwaterbear · 22nd June 2006, 06:25

Quote:

even if atmospheric pressure changes it shouldnt effect the calibration, since cells ARE a po2 device and are tied to pressure changes, if the person didnt calibrate correctly by putting in the correct surface pressure, then errors should be expected. The default 1000mb on the inspiration is not accurate for many locals.. Its not even the standard accepted atmosphere ( 1013 mb)

Well thats just the point...IME (which could easily be slanted) most inspo users just skip this step, so as you say, readings of a few % either side of 1 could be expected. Bottom line is it's easy just to recalibrate but the unit technically doesn't require recalibrating however since the absolute pressure experienced underwater will be near enough (notwithstanding the amount of air on top of th water) to the same as yesterday. BTW you forgot the 0.25 mb at 288.2K to be exact.

Andy, yep something to think about when you check your prism cal.

It's one of the features I really like about the prism and dislike about the inspo/evo: the prism doesn't make a robot out of you - you have to actually think about why you are seeing the readings you are getting rather than just push buttons, squirt squirt, dive.

***jradomski*** · 22nd June 2006, 06:56

Quote: (Originally Posted by Underwaterbear)

Well thats just the point...IME (which could easily be slanted) most inspo users just skip this step, so as you say, readings of a few % either side of 1 could be expected. Bottom line is it's easy just to recalibrate but the unit technically doesn't require recalibrating however since the absolute pressure experienced underwater will be near enough (notwithstanding the amount of air on top of th water) to the same as yesterday. BTW you forgot the 0.25 mb at 288.2K to be exact.

Andy, yep something to think about when you check your prism cal.

It's one of the features I really like about the prism and dislike about the inspo/evo: the prism doesn't make a robot out of you - you have to actually think about why you are seeing the readings you are getting rather than just push buttons, squirt squirt, dive.

if we really want to get anal
STP - 273.15 K, 32oF 101.325 kPa
NTP - 293.15 K, 68oF 101.325 kPa
SATP - 298.15 K and also 101 kPA
ISA - 101.325 kPa, 15 degC and 0% humidity

For the Trivia buffs

The highest recorded atmospheric pressure, 108.6 kPa occurred at Tosontsengel, Mongolia, 19 December 2001

The lowest recorded non-tornadic atmospheric pressure, 87.0 kPa (870 mbar or 25.69 inHg), occurred in the Western Pacific during Typhoon Tip on 12 October 1979

The highest sea-level pressure on Earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1032.0 mbar.

22nd June 2006, 02:02	#11 (permalink)
Underwaterbear A Prismer in Megland Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: May 2005 Location: Seattle, WA Posts: 198	Re: Calibration frequency requirements... Quote: It may not make sense, but at least with the classic when I try and check the cal after a few days its always been off by more than a few percent.. With the HH its almost always still been on, and in these cases I check the cells readings and if they changed by more than a few MV in oxygen, I'll keep a close eye on them for replacement (which is usually necessary).... It's more than likely that the difference you are seeing over a few days is related to changes in atmospheric pressure which may fluctuate by up to 5% between highs and lows.
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22nd June 2006, 02:57	#12 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,873	Re: Calibration frequency requirements... Quote: (Originally Posted by Underwaterbear) It's more than likely that the difference you are seeing over a few days is related to changes in atmospheric pressure which may fluctuate by up to 5% between highs and lows. Ahhh, never thought of this. Thanks, UB. I always assumed it was only necessary to cal day to day because of the cells slight decline, or not so slight decline, as the case maybe with a bad one. I do the electronic cal at the begining of every dive day, and if I get the same reading from the same batch of O2 on the analogue gage, I don't mess with it. Just got back from a trip, 40hrs of diving, adjusted the 2dry cal potts once at the begining, didn't have to mess with them again. -Andy
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22nd June 2006, 05:48	#13 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,113	Re: Calibration frequency requirements... Quote: (Originally Posted by Underwaterbear) It's more than likely that the difference you are seeing over a few days is related to changes in atmospheric pressure which may fluctuate by up to 5% between highs and lows. not really.. If calibrated properly, all the sensors should remain consitent and a loop flush with oxygen should result in a reading off the atmospheric pressure multiplied by the oxygen percentage of the source.. I don't assume its going to read 1.01 (insp is in bar) every day, every where.. even if atmospheric pressure changes it shouldnt effect the calibration, since cells ARE a po2 device and are tied to pressure changes, if the person didnt calibrate correctly by putting in the correct surface pressure, then errors should be expected. The default 1000mb on the inspiration is not accurate for many locals.. Its not even the standard accepted atmosphere ( 1013 mb) __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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22nd June 2006, 06:25	#14 (permalink)
Underwaterbear A Prismer in Megland Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: May 2005 Location: Seattle, WA Posts: 198	Re: Calibration frequency requirements... Quote: even if atmospheric pressure changes it shouldnt effect the calibration, since cells ARE a po2 device and are tied to pressure changes, if the person didnt calibrate correctly by putting in the correct surface pressure, then errors should be expected. The default 1000mb on the inspiration is not accurate for many locals.. Its not even the standard accepted atmosphere ( 1013 mb) Well thats just the point...IME (which could easily be slanted) most inspo users just skip this step, so as you say, readings of a few % either side of 1 could be expected. Bottom line is it's easy just to recalibrate but the unit technically doesn't require recalibrating however since the absolute pressure experienced underwater will be near enough (notwithstanding the amount of air on top of th water) to the same as yesterday. BTW you forgot the 0.25 mb at 288.2K to be exact. Andy, yep something to think about when you check your prism cal. It's one of the features I really like about the prism and dislike about the inspo/evo: the prism doesn't make a robot out of you - you have to actually think about why you are seeing the readings you are getting rather than just push buttons, squirt squirt, dive.
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22nd June 2006, 06:56	#15 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Join Date: Mar 2005 Location: "Da" Bronx Posts: 3,113	Re: Calibration frequency requirements... Quote: (Originally Posted by Underwaterbear) Well thats just the point...IME (which could easily be slanted) most inspo users just skip this step, so as you say, readings of a few % either side of 1 could be expected. Bottom line is it's easy just to recalibrate but the unit technically doesn't require recalibrating however since the absolute pressure experienced underwater will be near enough (notwithstanding the amount of air on top of th water) to the same as yesterday. BTW you forgot the 0.25 mb at 288.2K to be exact. Andy, yep something to think about when you check your prism cal. It's one of the features I really like about the prism and dislike about the inspo/evo: the prism doesn't make a robot out of you - you have to actually think about why you are seeing the readings you are getting rather than just push buttons, squirt squirt, dive. if we really want to get anal STP - 273.15 K, 32oF 101.325 kPa NTP - 293.15 K, 68oF 101.325 kPa SATP - 298.15 K and also 101 kPA ISA - 101.325 kPa, 15 degC and 0% humidity For the Trivia buffs The highest recorded atmospheric pressure, 108.6 kPa occurred at Tosontsengel, Mongolia, 19 December 2001 The lowest recorded non-tornadic atmospheric pressure, 87.0 kPa (870 mbar or 25.69 inHg), occurred in the Western Pacific during Typhoon Tip on 12 October 1979 The highest sea-level pressure on Earth occurs in Siberia, where the Siberian High often attains a sea-level pressure above 1032.0 mbar. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated. Last edited by jradomski : 22nd June 2006 at 08:12.
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