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!
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!
Hi Luke
I am guessing you are using an nRF52 series chip (If not please specify what chip you are using). The pins that can be used to measure voltage are the VDD pin, or one of the analog pins, AIN0 to AIN7.
Best regards,
Simon
Hi Simonr
Thanks for the reply. I am using the NRF52840. When I am measuring voltage from the same power source as powering the chip, the SAADC works fine, however if I connect it to a separate power source then step down the voltage as so using a resistor divider, the SAADC digital values suddenly increases exponentially. Please advise
Hi Luke
A likely problem is that you have to big values in the voltage divider, which causes strain on it and your measurements to be inaccurate. Please have a look at how to measure lithium battery voltage with the nRF52 for a thorough explanation on the matter.
Best of luck, and just ask if any problems persist!
Simon
Hi Simonr
Thank for the reply and various help. However I am encountering a quite a fair bit of fluctuations in the value when the voltage source is constant(on my multimeter).
I am using 12 bit resolution and a 1/6 gain. The ADC is connected to a 1M/100k voltage divider circuit with a 10nf cap. There is no oversampling and the code is triggered by an RTC timer every 400ms, set to low power mode and an acq time of 3us
<info> app: 5082.00
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Also, another puzzling issue is when connected to a 9v battery with common ground,
The measure voltage from ADC shows a drop of nearly 3v!
<info> app: 6.59
Measured voltage: 9.54 from multimeter
I am using the NRF52840 preview DK
Measuring 5v or VDD works fine however
************ Solved **************
Make sure the gain settings is within the voltage range
