This application note describes low flicker noise (0.1 Hz to 10 Hz band) measurement methodology and test setup recommendations for precision series references. Low noise measurement requires ultra-low setup noise, which can be achieved by selecting low-noise BOM for the band pass filter and proper design or layout techniques. The lowest noise reference REF54250CDR (flicker noise = 275 nV pk-pk with 100 μF capacitor on NR pin) is used to illustrate the component selection and board design to measure the noise floor with < 1.5% error from the measurement setup.