DIY Nitrox Analyzer (Arduino based)

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Well ran last night and again today. It does adjust less than 2PPM over an hour but doesn’t change quickly. As to how fast it reacts on a tank, I don’t have one with CO to test, but running while I solder near it, it reacts pretty quick. The sensor is wired with a resistor as the spec calibration is in nanoamps. I started here. Then, like my O2 analyzer, I used an ads1115 and an arduino nano.
At this point even if it is not accurate, I know it reacts. A normal tank shouldn’t show much or nothing. If I get a reading of 5+ PPM, it will be worth questioning the tank. Hopefully, more testing and tweaking over the summer, if the virus lets me get out to dive this year.
 
Making progress.....
analyzer0.jpg analyzer1.jpg analyzer2.jpg
Wheatstone bridge with the MD62 sensor is surprisingly fast when some helium flows over it.
Programming works fine, next job is a small tube with air in/out, sensors built into it.
 
IMG-20200427-WA0019.jpeg

First version ready.

Several topics on SB helped me a lot with in-depth information about the theoretical versus real-life behavior of the O2 cells.
I added 100% O2 calibration and 100% He calibration.

In 100% He, after >1 minute the O2 cell still produces 0.25mV. I compared this with the cell from my analog nitrox analyzer - same behavior.

Since I don't have any old cells (I knew I should not have trashed them), could somebody do some measurements with old cells (2 years)? Voltage in air / 100% O2 / 0% O2.
 
Guys, can someone help...

I`m trying to build this, i`m using an Arduino with an ADS1118 ADC (16bit ADC). I have the O2 cell connected to A0 and A1 and I`m measuring in differential mode, but I'm getting zero mV?
The cell is supposed to be functional....

James
 
Guys, can someone help...

I`m trying to build this, i`m using an Arduino with an ADS1118 ADC (16bit ADC). I have the O2 cell connected to A0 and A1 and I`m measuring in differential mode, but I'm getting zero mV?
The cell is supposed to be functional....

James

Do you have a multimeter? Can you check the cell? What library does the ADS1118 use? There are specific configurations peculiar to what you are trying to do. The ADC does not output a voltage but "talks" to the MCU via the I2C bus.

You can also feed the ADC a "dummy" voltage using a pot as a divider.
 
Guys, can someone help...

I`m trying to build this, i`m using an Arduino with an ADS1118 ADC (16bit ADC). I have the O2 cell connected to A0 and A1 and I`m measuring in differential mode, but I'm getting zero mV?
The cell is supposed to be functional....

James

I found a library on GitHub. It looks like the parameters are different and it uses the SPI instead of the I2C bus. Sampling is also different. You will have to re-write the code and change the wiring connections for that.
 
Do you have a multimeter? Can you check the cell? What library does the ADS1118 use? There are specific configurations peculiar to what you are trying to do. The ADC does not output a voltage but "talks" to the MCU via the I2C bus.

You can also feed the ADC a "dummy" voltage using a pot as a divider.

Thanks, but chatting with Miyaru it would appear that me cell is dead (zero mV output). Interestingly, I just took it apart and there is about 200mV coming from the wires of the galvanic cell. So i`lll try n figure out if its an electronic component problem of the cell.
 
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Yes, I`m using the ADS1118 library with my own code.
 
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Thanks, but chatting with Miyaru it would appear that me cell is dead (zero mV output). Interestingly, I just took it apart and there is about 200mV coming from the wires of the galvanic cell. So i`lll try n figure out if its an electronic component problem of the cell.

200 mV is too high for an O2 cell.
 
https://www.shearwater.com/products/teric/

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