CO2 sensor for low volumes

Hi,

I'm a student in medical engineering, looking for a new CO2 sensor for my veterinary support setup. What I'm looking for is to monitor the CO2 level in mice and rats exhalation. We are talking about ~4ml of tidal volume (volume per breath), which is a crucial factor. The update rate should be at least 4sec / 0.25Hz, while the range I'm looking for is max 100'000ppm / 10%. Even 5% could actually be fine.
Right now I have two K33 30% CO2 sensors, which seems perfect, but unluckily they stopped working so I'm looking for an alternative.
Also, the sensor must offer I2C / UART connection, in order to interface it with a microcontroller.

Any advice is really appreciated!
Rodolfo

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fmilburn over 3 years ago

This isnt an area where I have much knowledge but did you look at the Sensiron STC-31? https://sensirion.com/media/documents/7B1D0EA7/61652CD0/Sensirion_Thermal_Conductivity_Datasheet_STC31_D1_1.pdf
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michaelkellett over 3 years ago in reply to fmilburn

That's an interesting part. Quite slow, (66ms) and poor accuracy at low CO2 levels. It works by measuring thermal conduction (of the gas I think) and is sensitive to thermal gradients but the data sheet doesn't go into details.

MK
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michaelkellett over 3 years ago in reply to fmilburn

That's an interesting part. Quite slow, (66ms) and poor accuracy at low CO2 levels. It works by measuring thermal conduction (of the gas I think) and is sensitive to thermal gradients but the data sheet doesn't go into details.

MK
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Runzolf over 3 years ago in reply to michaelkellett

The undetailed datasheet is quite annoying, or maybe it just states that the sensor is just a "ON / OFF" type, so the datasheet just describes in which LED working frequency range is more effective.

Couldn't find it at higher-res:

There is also an evaluating kit sold, which is basically the LED and the tube already built, which could save me a lot of hassle. It doesn't specify how powerfull should the LED be, it should depend on the NEP right? It states 2.7*10e-10 on the cheaper one, and "mean 70" on the dual sensor one. What ranges should I look for, in case I really wanted to go down that road?
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fmilburn over 3 years ago in reply to Runzolf

I would get in touch with Sensiron
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Runzolf over 3 years ago in reply to fmilburn

Oh, I think I replied to the wrong parent comment, I was talking about the KEMET. But for sure, I will get in contact with them.
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