[SAADC] how to measure battery with more precision digits

RE: [SAADC] how to measure battery with more precision digits

Louis — Wed, 09 Aug 2017 07:23:47 GMT

I do not fully understand nordic SAADC. Thanks for the reply.

RE: [SAADC] how to measure battery with more precision digits

Roger Clark — Wed, 09 Aug 2017 06:09:19 GMT

nRF52832 has a 12 bit ADC, and the spec says

"14-bit resolution with oversampling"

This is 2 bits better than the nRF51's ADC

I'm not sure however I fully understand your problem.

If your resistor divider is 1500k and 430k , you can measure up to voltages of 4.246V as that divides to 3.3V at the ADC

For for a 10 bit ADC, thats 1024 steps so 4.246 / 1024 = 0.004V resolution. Which is better than you now say you require.

However....

I think you do not fully understand the operation of an ADC. See devzone.nordicsemi.com/.../

So you need you either need to use much lower value resistors (which may be impractical as it would flatten the battery). Or you need to implement a circuit described here

devzone.nordicsemi.com/.../

RE: [SAADC] how to measure battery with more precision digits

Louis — Wed, 09 Aug 2017 05:53:03 GMT

Roger, thanks for quick reply. Does that mean no way to measure battery voltage with 0.01V precision by nrf52832?

RE: [SAADC] how to measure battery with more precision digits

Roger Clark — Wed, 09 Aug 2017 03:33:21 GMT

If you need more than 10 bit resolution, you would need to use an external ADC to measure the voltage, which has more than 10 bit resolution.

You could investigate oversampling the internal ADC e.g. See

www.embedded.com/.../Oversampling-with-averaging-to-increase-ADC-resolution

However, this is a far from optimal solution, hence why you can buy 20 bit ADC's

You also start to need to consider the stability of your voltage reference when you are measuring to these sorts of resolution.