Measuring external voltage of a different power source

[Luke.L]

Hi,

    May I know what is the hardware layout for measuring external voltage using SAADC? I may not be understanding the infocenter or the datasheet for setting the external reference pin

Thank you!

[Simonr]

Hi Luke

You can try to calibrate your nRF52840 for more accurate measurements. This link should be helpful. As the calibration data get saved in flash, you should just have to do this once.

Best regards,

Simon

[Luke.L]

Thanks Simonr, I see an improvement here:

<info> app: SAADC HAL simple example started.
<info> app: 9.72

<info> app: 9.79

<info> app: 9.75

<info> app: 9.73

<info> app: 9.66

<info> app: 9.67

<info> app: 9.76

<info> app: 9.70

<info> app: 9.72

<info> app: SAADC calibration complete !

<info> app: 9.57

<info> app: 9.51

<info> app: 9.48

<info> app: 9.58

<info> app: 9.55

<info> app: 9.56

<info> app: 9.53

<info> app: 9.56

<info> app: 9.59

<info> app: 9.55

However are those slightly variations still within the ADC tolerances? Also how often should I calibrate as this device will be in an environment with temp variations, from night->day for example