diff --git a/src/thermostat/max1968.rs b/src/thermostat/max1968.rs
index 9221f85..13fe147 100644
--- a/src/thermostat/max1968.rs
+++ b/src/thermostat/max1968.rs
@@ -125,7 +125,17 @@ impl MAX1968 {
             .default_sample_time(config::SampleTime::Cycles_480);
         // Do not set reset RCCs as it causes other ADCs' clock to be disabled
         let mut pins_adc1 = Adc::adc1(adc1, false, adc_config);
-        pins_adc1.calibrate();
+        
+        // adc1.calibrate() fn only read REFINT once to assign the calibration value.
+        // It does not take the STM32F4's ADC Precision Limitation into account.
+        // AN4073: ADC Reading Dispersion can be reduced through Averaging
+        let mut vdda_mv: u32 = 0;
+        for _ in (0..512).rev() {
+            pins_adc1.calibrate();
+            vdda_mv += pins_adc1.reference_voltage();
+        }
+        vdda_mv = vdda_mv / 512 as u32;
+        pins_adc1.apply_config(adc_config.reference_voltage(vdda_mv));
 
         let adc_config  = AdcConfig::default()
             .clock(config::Clock::Pclk2_div_8)