I can't really figure out how the output voltage relates to the oxygen concentration.

It says 7-12mV in ambient air, which would be 20% oxygen (more or less).
Of course we don't know how linear that is from 0% to 20%.

 

It says 7-12mV in ambient air, which would be 20% oxygen (more or less).
Of course we don't know how linear that is from 0% to 20%.

It does specify accuracy and linearity at 3%, but 7mV to 12mV in ambient air is 9.5mV±26%.
If it can't do better than ±26% I don't know why we were all worrying about 3mV offset error!

 

I don't know why we were all worrying about 3mV offset error!

Perhaps the absolute offset, not so much, but certainly the offset drift with temperature could be.

 

I don't know why we were all worrying about 3mV offset error!

Hi,
I am not worrying about the offset error, as I said earlier it can be trimmed out, as is often the requirement when using OPA's in low level applications.

The same trimming is also often required in order to get the required Span on the Vout voltage

E

 

I just received one of these sensors.

I'll give it a try within in few days and see if the specs comply with my measurements; so sure is sure

 

hi @flotul
Please explain the purpose and how this Oxygen measuring device/project will be used?

Moderation

 

I'm building an Oygen anayzer for nitrox blending - diving purpose.

 

I'm building an Oygen anayzer for nitrox blending - diving purpose.

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I would strongly recommend against doing this with a homebuilt circuit, especially given the very limited understanding of circuit design indicated here. This is life critical stuff. Would YOU be comfortable having someone you cared about getting their nitrox tanks from someone that was using a DIY circuit designed by someone that has little to no experience designing circuits? Are you going to be comfortable that their DIY circuit is going to be good enough as the temperature changes? That it is going to be good enough after months or years of use without being certified or calibrated? That it is going to be good enough as the battery voltage fluctuates?

 

Thanks for all your thoughts I completely share with you, Wbahn.

For now, I'm starting this circuit from its very basics, learning to know the different elements it will be composed of and what their gotchas I'll need to discover.

Even if I make it, it doesn't mean I will be using it without having a "commercial" (certified or whatever it is) analyzer in parallel.

As many of us, I want to understand how it works, what it needs to do so and how reliable it may be. All this may also help me to understand why those commercial analyzer are so expensive. BTW, I own a commercial analyzer (see picture in previous post).

 

Thanks for all your thoughts I completely share with you, Wbahn.

For now, I'm starting this circuit from its very basics, learning to know the different elements it will be composed of and what their gotchas I'll need to discover.

Even if I make it, it doesn't mean I will be using it without having a "commercial" (certified or whatever it is) analyzer in parallel.

As many of us, I want to understand how it works, what it needs to do so and how reliable it may be. All this may also help me to understand why those commercial analyzer are so expensive. BTW, I own a commercial analyzer (see picture in previous post).

This is a reasonable objective and approach.

Though you aren't likely to gain an understanding of why the commercial analyzers are so expensive. The driver behind the price is two-fold. First, economies of scale -- the number of units sold is going to be relatively small and so all of the design, development, testing, and tooling (i.e., the NRE - non-recurring engineering expenses) are going to amortized over a relatively small number of units (compare it to, for instance, the number of units that the NRE gets spread over if you are selling, say, smoke detectors). But the big driver of the price on something like this is going to be the liability insurance premiums. The manufacturer is going to be a target for lawsuits any time a diver is injured or dies and one of these units was involved, even if it is pretty obvious that the unit did not contribute to the incident. Worse, they can be sued decades after the unit was originally sold and even if the person that used it found it in a trash bin at a recycling plant. All they have to do is convince a jury that the family of the injured/deceased party needs to be compensated somehow, someway, by someone. That kind of liability protection is extremely expensive and the cost has to be included as part of the price charged.