https://devzone.nordicsemi.com/f/nordic-q-a/20270/nrf51822-adcWe have a application that use the ADC of nRF51822 to detect a variable resistance (schematic is attached). The current passing through the variable resistor should be around 1uA, It means that the R1and R2 should be very large. Up to I know the ADC shoulden-USTelligent Community 13Wed, 08 Mar 2017 02:32:30 GMThttps://devzone.nordicsemi.com/thread/78963?ContentTypeID=1Wed, 08 Mar 2017 02:32:30 GMT137ad170-7792-4731-bb38-c0d22fbe4515:7e396f87-42d7-4bf4-936c-48bc869b9f86Roger Clark<p>See this answer</p> <p><a href="https://devzone.nordicsemi.com/question/3512/adc-reference-selection-nrf51822/">devzone.nordicsemi.com/.../</a></p> <p>&quot; The impedance of the input voltage source, i.e. the device that generates the voltage to be measured by the ADC input pin, must be low, preferably within 1 kohm&quot;</p> <p>Your circuit will have an input impedance of approx 300k ohms</p> <p>i.e 300 times more than recommended by Nordic</p><div style="clear:both;"></div>