Nitrox/Trimix & CO analyzer

[estresao]

Hi all,

I've made my own version using similar approach and it's working fine..... actually I'm already using it in my nitrox stick (so far I only blend Nx).

I've got a couple of questions:

- I have my O2 sensors connected directly to the ADS1115, but I've found in some datasheet a load resistance is recommended. In the schematic shared here it seem you guys went for the same approach of no load resistor... have you ever considered using some?

- My implementation reads up to two O2 cells to extend it in near future for He support, but so far, the two O2 values are just displayed as independent O2 values. This is OK for me so far, and it allow me to use both sensor at the same time to test some O2 cells I've given from rebreathers and so on, this way I'm always have one which I know it works properly, and the another under test (or to double check to avoid wrong values when one get wore. OK.... the point is that initially I've tried to connect both to same ADS1115 but I've found there where some interferences affecting the values, so I ended up using two ADS1115, did that happened to you guys? I see in the schematic you are also using two ADS1115 but for different reason.

 

[Steve78]

Hi,
I am also working on my trimix analyzer and found a strange thing related to the ZE07 CO sensor.
I use separate ADS1115 for the O2/He and for CO detection. I use the DAC output of the CO module, 0.4 -2 volts. I calibrate the CO sensor with 100% oxygen, this case it shows about 404 mV / 0ppm. In normal air it goes a bit higher, 408 mV / 1.2 ppm. And it fluctuates between these two values and stabilize at one of them for a few seconds. This case there is no gas flow through the analyzer so it might be saturation of the sensor.
When I connect my trimix tank (I have already used for diving) CO level goes up to 15ppm. If I leave the gas flow through the analyzer it slowly goes down to the original value, 408 mV/1.2 ppm.

Is it a normal behaviour?
Any experince?