Measuring Voltage for Teensy 3.x

[jakorten]

I am working on a project where accurate analog sensor reading is important due some math that we run over it.

I want to be able to see the supply voltage that is given to our teensy. I was thinking about using something like this:

http://media.digikey.com/PDF/Data Sheets/Maxim PDFs/MAXQ314.pdf

Maybe an alternative would be the TI INA 219:
INA219

There seems to be someone that has experience with it for Arduino and even provides a library/
Article


Does anyone in here have experience with this chip or the alternative or are there other easier solutions?

Sincerely,
Johan

(I actually also just found: http://forum.pjrc.com/threads/17369...ha-Clock-Five-quot-Project-using-the-Teensy-3)

 

[Constantin]

The Teensy has a fairly usable ADC, so the question is: how accurate do you need this bus monitoring to be? One of the key upgrade potentials is the use of a accurate external ADC. There are a number of them with libraries. Your component selections also looked pretty usable.

However, you might find that the internal ADC is 'good enough', as long as you use a shunt reference, extra capacitors for AREF, and a 0.01uF Cap from analog to AGND for the signal. Ideally, you'd also use a buffer chip to make the signal low impedance but as long as you keep the input impedance below 1-2kOhm, you should be able to achieve 13 bits of resolution. With averaging / decimation, the resolution might be even higher.

Stabilizing the Teensy power supply further is a possibility, i.e. adding a 100uF + 1uF cap on the VUSB as well as on 3.3V power supply pins to help the internal regulator maintain a good voltage.

 

[jakorten]

Well, of course I know that the ADC is very usable otherwise I would never have chosen the teensy in the first place. But if one has a battery powered system, we see minor variations but due to the extensive math that we do, the variations become significant enough so that we want to make the constant voltage factor that we now use variable and update it real time. A different system will have a different voltage, no matter what, what is why we want to measure the voltage. But your suggestions are good ones to take into consideration!