Alternatives to Galvanic Fuel Cells?

PacketSniffer

So, recently armed with the knowledge to not put complete trust in galvanic fuel cells (i.e., O2 sensors), I'm left wondering if it's possible to measure the loop PO2 with a more safe, reliable method in a close-enough cost range. I'm not an electrical engineer so I always need to double my efforts to understand something in that realm. I'm sure I can't be the first person to inquire about this. Is there a more reliable method?

A 5 second Internet search shows that there are indeed a few other methods to choose from. But, are any of them feasible for our application?

Oxygen Sensor
There are many different ways of measuring oxygen. These include using technologies such as zirconia, electrochemical (also known as Galvanic), infrared, ultrasonic and very recently laser. Each method has its own advantages and disadvantages.

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Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat.

nigelh

Sadly we want to measure ppO2 where the absolute pressure can exceed 10bar and in 100% condensing humidity.
The only one that has been available up to now that meets that is the galvanic and to even get close to a tolerable reliability we need at least three.

We all live in hope of compact, cheap, reliable mass spectrometry (so we can read out CO2 as well) but currently the vacuum pump and the cryogenics in portable format elude us.

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nigelh

PacketSniffer

Maybe this company (OxiGraf) would be interested in developing something for our application.


How Does the Oxigraf Sensor Work?

• The patented Oxigraf sensor uses laser diode absorption spectroscopy in the visible spectrum, similar to the absorption method used to measure CO2, N2O, and anesthetic agents in the infrared spectrum.
• However, oxygen absorption is in a region of the visible spectrum (760 nm) where there is no interference or absorption by other ventilation or anesthetic gases.
• Also the emission line width of the laser and the absorption line width of O2 are very narrow, less than 0.01 nm, compared to perhaps 100 nm for the CO2 absorption band at atmospheric pressure.
• The spectrally pure laser is thermally tuned precisely to the oxygen absorption line.
• As the oxygen concentration increases, the light intensity is attenuated, and the photodetector response varies linearly with the oxygen concentration.

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Laser Diode Oxygen Analysis

Oxigraf performed an SBIR for the US Air Force to develop a portable and rugged laser diode oxygen sensor for monitoring aircrew oxygen concentrators.
The sensor measures oxygen (O2) concentrations from 21% to 100%. It operated quickly and accurately over an altitude range of 1000 to 70,000 feet (pressure range of about 120 to 5 kPascal or about 18 to 1 psig).
The sensor will alternatively display the partial pressure of oxygen.
The sensor was tested to measure over a temperature range from -50 deg C to 55 deg C with 0.5% accuracy and response time (10-90%) of 400 milliseconds at a flow rate of 50 ml/min.
The sensor was also shown to operate over a Mil Spec vibration schedule.
Power requirements are 28 volts, 25 watts at turn-on and 10 watts for operation.
When coupled with a notebook or palmtop computer, the system serves as an oxygen flight data recorder.
Potential applications include monitoring On-board Oxygen Generation Systems (OBOGS), field portable oxygen generation systems, and fuel tank inert gas generators. In another project, Oxigraf performed manufacturability engineering, contract manufacturing, and product service for a manufacturer of cardio-pulmonary gas exchange analyzers. Laser diode oxygen sensors were qualified, replacing a paramagnetic sensor and providing faster rise times and less sensitivity to vibration. A controller board was designed incorporating all gas, pressure, and temperature sensors together with control firmware. The analyzer and software were qualified to UL, CSA, and CE standards.


Oxigraf offers to apply its unique, patented, and low cost laser diode technology to your oxygen analysis needs in medical, combustion, chemistry, telecomm, and air quality applications.
©

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Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat.

PacketSniffer

Oh, wow, here are the OEM analyzers.

And get this..... They already have a OEM O2 and CO2 package!!! Hmm ,I wonder how big it is? lol


The X2014 Oxygen Sensor combines into a single package, a CO2 sensor and the well known Oxigraf X2004 sensor.

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Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat.

caver95

Very nice, How much?

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PacketSniffer

LOL...Yes, another one of the big questions. So, the list is as follows:

1) How big?
2) How much?


I'm going to call them on Monday to see what I can find out.

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Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat.

EBT

Might I suggest;

1. Performance in a humid environment
2. Power requirements.

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Sutty

Doesn't look very big looking at the chips/pins. Worth asking about power supply and power consumption as well though.

Neil

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PacketSniffer

If I'm reading the spec sheet correctly on the x2004, it shows from 5 to 95% relative humidity.

I noticed the power requirements were pretty needy. However, did you notice the accuracy with which these are capable of??? OMG. "It has a resolution of 0.02% oxygen and accuracy of +- 0.2% in air mixtures with a response time of 100 ms at 200 ml/min." I don't think we need it that accurate. So, maybe the power could be stepped down.

If we can get a accurate, reliable, measurement, I'm willing to strap on another cannister battery just for this type of performance (and stress-free diving).

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Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat.

PacketSniffer

When I call, I'll inquire if they have something currently in the making or if it is possible to develop something along this criteria:


1) Small enough to feasibly integrate into SCUBA
2) Operate on battery power for at least 12 hours (hopefully longer)
3) Measure the oxygen partial pressure from .10 to 2.0
4) Response 90%: 6 seconds or better (they have this capability already)
5) Life expectancy: 5 years or more
6) Operate in condensing environment of 100% relative humidity (they have this capability already as well at 95% RH)
7) Measure CO2 from 0.5%
8) Easy, on-site calibration to prove a linear progression from .10 to 2.0 partial pressure. Ideally, this would take place at 1 ATM.
9) Calibration valid for at least 12 hours

Does this seem reasonable?

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Far better it is to dare mighty things, to win glorious triumphs, even though checked by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat.