Homemade PO2 meter

marekm · 26th March 2007, 19:33

Hi eveyone,

I've just finished my first attempt at a dual display PO2 meter. The meter is at 1ata pressure internally (not ambient), is magnet free, has a backlight that can be switched on underwater and has PCB's coated in lacquer. I have pressure tested it to 80m, but it can be filled with paraffin oil to go deeper. The end of the cable has a 1/4" Swagelok fitting that can be used on Hammerhead Inspo heads or any other rebreather with these threads. The cost of parts was ~AU$80 and it took a few days to make (mainly due to the R&D).

A detailed breakdown can be seen here:
New Page 1

Any comments, criticisms or questions welcome.
-Marek

pete611 · 27th March 2007, 00:47

cool....it work. 2 sensor why not 3

Tom Rose · 27th March 2007, 00:57

Very Nice Work

Tom

marekm · 27th March 2007, 02:27

Quote: (Originally Posted by pete611)

cool....it work. 2 sensor why not 3

Couple of reasons:
1. Could not fit a third panel meter into the housing without making the tube too long to mount on my arm.
2. The panel meter is the same as the one used in El Cheapo II oxygen analyzers, so the wiring becomes too complex with a third panel meter. If you need three, different panel meters should be used.
2. Only have two O2 sensors to work with, and if they don't agree with each other, I bail out.
3. A VR3 can be used to monitor PO2 on the third cell if you have one.

-Marek

montyg · 27th March 2007, 07:54

Quote: (Originally Posted by pete611)

cool....it work. 2 sensor why not 3

This article by Dale Bletso titled "One, two, three, four, what's the magic number?" always makes interesting reading.

Thanks Mr Bletso!

How many sensors

rgds
monty

Tom Rose · 27th March 2007, 12:59

Quote: (Originally Posted by montyg)

This article by Dale Bletso titled "One, two, three, four, what's the magic number?" always makes interesting reading.

Thanks Mr Bletso!

How many sensors

rgds
monty

I came to the same conclusion years ago that Mr. Bletso has for the same reasons. I never put it down so well. In summary, if you are the computer, and things don't make sense, get the hell out of the water.

I always remind myself that this dive is of no importance....it is the next thousand dives that are important....screwing up this one can prevent the next thousand.

A safe and long diving career

Tom

bletso · 28th March 2007, 00:00

Well Guys, I am flattered. Thanks. I still use my homemade two sensor array and it works great.

Dale

Bnscherm · 28th March 2007, 19:49

Marek,

Looks good!

I haven't dove the display that I've built yet, but I've all ready been redesigning it for some new displays that I've found.

Lascar Electronics

Two or three of these with a lithium camera battery would make an awesome compact little backlit display. Only problem is they cost $50US each! Although, samples can be had for $36. I think I'll work out the kinks before I consider upgrading...

marekm · 28th March 2007, 20:05

Hi Bnscherm,

I have had a look at these DPM's at the local technical dive equipment shop, but at AU$60 a piece, they are far more expensive than the AU$13 DPM's I used for my dual PO2 meter. In the process of designing, building and redesigning PO2 meters I have gone through 7 of these DPM's, and destroyed a couple in the process. Given my new found DIC philosophy of diving (Doing It Cheap

), I have found that a large $13 DPM does the exact same job as a smaller $60 DPM, but costs much less. Eventually when the PO2 meter housing is checked out after a series of dives, and my paraffin oil filled PO2 meter does not fail, I'll consider building a tiny PO2 meter array with these DPMs. Then again, I'm thinking of making a fully analog LED light based PO2 monitor that uses only transistors, diodes and resistors to light up a series of LED's that indicate PO2 between 0.2 or less and 1.6 or more, so depending on how that works out I may or may not go with the smaller DPM's

Cheers.
-Marek

Tom Rose · 28th March 2007, 21:50

Quote: (Originally Posted by marekm)

Then again, I'm thinking of making a fully analog LED light based PO2 monitor that uses only transistors, diodes and resistors to light up a series of LED's that indicate PO2 between 0.2 or less and 1.6 or more, so depending on how that works out I may or may not go with the smaller DPM's

Cheers.
-Marek

You should go look at.....

CEDU FEOR Light, with Heads Down Display

Dr Bob strikes again...

Tom

26th March 2007, 19:33	#1 (permalink)
marekm Banned Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Oct 2006 Location: Brisbane, Australia Posts: 196	Homemade PO2 meter Hi eveyone, I've just finished my first attempt at a dual display PO2 meter. The meter is at 1ata pressure internally (not ambient), is magnet free, has a backlight that can be switched on underwater and has PCB's coated in lacquer. I have pressure tested it to 80m, but it can be filled with paraffin oil to go deeper. The end of the cable has a 1/4" Swagelok fitting that can be used on Hammerhead Inspo heads or any other rebreather with these threads. The cost of parts was ~AU$80 and it took a few days to make (mainly due to the R&D). A detailed breakdown can be seen here: New Page 1 Any comments, criticisms or questions welcome. -Marek
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27th March 2007, 00:47	#2 (permalink)
pete611 RBD one dive at a time... Current Rebreather/s: Dolphin Other Rebreather/s: Dolphin Join Date: Feb 2006 Location: Puerto Rico Posts: 223	Re: Homemade PO2 meter cool....it work. 2 sensor why not 3
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27th March 2007, 00:57	#3 (permalink)
Tom Rose Still Learning Current Rebreather/s: Other CCR Home Build Other Rebreather/s: Prism Topaz Other CCR Home Build Join Date: Oct 2005 Location: USA,North Carolina Posts: 331	Re: Homemade PO2 meter Very Nice Work Tom __________________ The 50-50-90 rule: Anytime I have a 50-50 chance of getting something right, there's a 90% probability I'll get it wrong the first time. www.atlimp.com
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27th March 2007, 02:27	#4 (permalink)
marekm Banned Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Oct 2006 Location: Brisbane, Australia Posts: 196	Re: Homemade PO2 meter Quote: (Originally Posted by pete611) cool....it work. 2 sensor why not 3 Couple of reasons: 1. Could not fit a third panel meter into the housing without making the tube too long to mount on my arm. 2. The panel meter is the same as the one used in El Cheapo II oxygen analyzers, so the wiring becomes too complex with a third panel meter. If you need three, different panel meters should be used. 2. Only have two O2 sensors to work with, and if they don't agree with each other, I bail out. 3. A VR3 can be used to monitor PO2 on the third cell if you have one. -Marek
(Offline)

27th March 2007, 07:54	#5 (permalink)
montyg Monty Guest Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Feb 2007 Location: Cape Town, South Africa Posts: 242	Re: Homemade PO2 meter Quote: (Originally Posted by pete611) cool....it work. 2 sensor why not 3 This article by Dale Bletso titled "One, two, three, four, what's the magic number?" always makes interesting reading. Thanks Mr Bletso! How many sensors rgds monty
(Offline)

27th March 2007, 12:59	#6 (permalink)
Tom Rose Still Learning Current Rebreather/s: Other CCR Home Build Other Rebreather/s: Prism Topaz Other CCR Home Build Join Date: Oct 2005 Location: USA,North Carolina Posts: 331	Re: Homemade PO2 meter Quote: (Originally Posted by montyg) This article by Dale Bletso titled "One, two, three, four, what's the magic number?" always makes interesting reading. Thanks Mr Bletso! How many sensors rgds monty I came to the same conclusion years ago that Mr. Bletso has for the same reasons. I never put it down so well. In summary, if you are the computer, and things don't make sense, get the hell out of the water. I always remind myself that this dive is of no importance....it is the next thousand dives that are important....screwing up this one can prevent the next thousand. A safe and long diving career Tom __________________ The 50-50-90 rule: Anytime I have a 50-50 chance of getting something right, there's a 90% probability I'll get it wrong the first time. www.atlimp.com
(Offline)

28th March 2007, 00:00	#7 (permalink)
bletso An independent diver. Current Rebreather/s: Dolphin Home Build Other Rebreather/s: Dolphin Home Build Join Date: May 2006 Location: Louisville, KY, USA Posts: 263	Re: Homemade PO2 meter Well Guys, I am flattered. Thanks. I still use my homemade two sensor array and it works great. Dale
(Online)

28th March 2007, 19:49	#8 (permalink)
Bnscherm New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Not Bought Yet Join Date: Nov 2006 Location: Michigan, USA Posts: 29	Re: Homemade PO2 meter Marek, Looks good! I haven't dove the display that I've built yet, but I've all ready been redesigning it for some new displays that I've found. Lascar Electronics Two or three of these with a lithium camera battery would make an awesome compact little backlit display. Only problem is they cost $50US each! Although, samples can be had for $36. I think I'll work out the kinks before I consider upgrading...
(Offline)

28th March 2007, 20:05	#9 (permalink)
marekm Banned Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Oct 2006 Location: Brisbane, Australia Posts: 196	Re: Homemade PO2 meter Hi Bnscherm, I have had a look at these DPM's at the local technical dive equipment shop, but at AU$60 a piece, they are far more expensive than the AU$13 DPM's I used for my dual PO2 meter. In the process of designing, building and redesigning PO2 meters I have gone through 7 of these DPM's, and destroyed a couple in the process. Given my new found DIC philosophy of diving (Doing It Cheap ), I have found that a large $13 DPM does the exact same job as a smaller $60 DPM, but costs much less. Eventually when the PO2 meter housing is checked out after a series of dives, and my paraffin oil filled PO2 meter does not fail, I'll consider building a tiny PO2 meter array with these DPMs. Then again, I'm thinking of making a fully analog LED light based PO2 monitor that uses only transistors, diodes and resistors to light up a series of LED's that indicate PO2 between 0.2 or less and 1.6 or more, so depending on how that works out I may or may not go with the smaller DPM's Cheers. -Marek
(Offline)

28th March 2007, 21:50	#10 (permalink)
Tom Rose Still Learning Current Rebreather/s: Other CCR Home Build Other Rebreather/s: Prism Topaz Other CCR Home Build Join Date: Oct 2005 Location: USA,North Carolina Posts: 331	Re: Homemade PO2 meter Quote: (Originally Posted by marekm) Then again, I'm thinking of making a fully analog LED light based PO2 monitor that uses only transistors, diodes and resistors to light up a series of LED's that indicate PO2 between 0.2 or less and 1.6 or more, so depending on how that works out I may or may not go with the smaller DPM's Cheers. -Marek You should go look at..... CEDU FEOR Light, with Heads Down Display Dr Bob strikes again... Tom __________________ The 50-50-90 rule: Anytime I have a 50-50 chance of getting something right, there's a 90% probability I'll get it wrong the first time. www.atlimp.com
(Offline)

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