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do I need capacitor to use adc??

From this (https://devzone.nordicsemi.com/b/blog/posts/measuring-lithium-battery-voltage-with-nrf51), there is capacitor connected to adc input pin. 

But is it necessary to have the capacitor? what is there is no cap connected to adc input pin? is it possible to measure voltage? 

Thank you. 

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  • Hi,

    You do not always need a capacitor. It depends on the circuit you are measuring. There is a current inflow to the ADC peripheral when it is measuring (charging an internal capacitor), and this will affect the voltage you are measuring. In the post you link to, this would result in a lower voltage over the resistor you are measuring, causing you to measure a too low voltage. A possible solution is to use a capacitor as suggested. The blog has a fairly good explanation of the reasoning behind this choice.

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  • Hi,

    You do not always need a capacitor. It depends on the circuit you are measuring. There is a current inflow to the ADC peripheral when it is measuring (charging an internal capacitor), and this will affect the voltage you are measuring. In the post you link to, this would result in a lower voltage over the resistor you are measuring, causing you to measure a too low voltage. A possible solution is to use a capacitor as suggested. The blog has a fairly good explanation of the reasoning behind this choice.

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