More ADC inputs?

Hello

I will be using 5 analog sensors but each sensor has 2 analog outputs readings. So I will need 10 analog inputs ADC. See picture.

How could I do that with only a Particle Boron?

Thanks in advance

The ADCs on the nRFs are not the best to begin with, so you may be best served with a dedicated ADC chip.

However, what are the Vref signals actually doing?

Hello @ScruffR!
The Vref output acts as
the reference voltage for zero concentration even as the battery voltage decreases. Measuring Vref in-situ
compensates for variations in battery or supply voltage, minimizing these effects on the real output.

Why is not the best to begin with?
Which ADC chip do you recommend me and how to connect to the Boron?

Doesn’t this mean all Vref signals may be round about the same value?

It’s just a HW flaw.
You may want to look at this video of Andreas Spiess

It’s not specifically talking about the nRF but ESP, but the issue is pretty much the same (if not worse) on the nRFs.

I will see the video. @ScruffR how about using 8 ADC to I2C converters ? Because I will use 4 sensors (each one with Vgas and Vref outputs)

P.S. Vref is changing according some parameters like temperature and it is used in an math equation for getting the right measure.

Yup, that would be what I’d use for max accuracy.
If you have some less important readings you could get away with them on the Boron itself and the more important ones on a single external 8 channel ADC board.

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Thanks so much. I will look a ADC to I2C 8 channels up for that purpose, I think Adafruit should have it.

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Just flipping through the datasheets on those. It looks like you want to make sure you’re reading vref in a high impedance way.

As you have to buffer that anyway, have you considered using an amp to do the subtraction and just dealing with 5 signals?

If I found the document you’re looking at they are adding a buffer to vref. I’m not sure why they’re doing the subtraction in the uC though.

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I think they are using a math equation, but you are right I’m not sure why they’re doing the subtraction in the uC though.

P.S. Good idea of using an amp to do the substraction, but I dont know if it will work.