diff --git a/platform/zoul/dev/adc-sensors.h b/platform/zoul/dev/adc-sensors.h
index 501eaa564..769e9d97c 100644
--- a/platform/zoul/dev/adc-sensors.h
+++ b/platform/zoul/dev/adc-sensors.h
@@ -66,7 +66,7 @@
 #define ADC_WRAPPER_SUCCESS                 0x00
 #define ADC_WRAPPER_ERROR                   (-1)
 #define ADC_WRAPPER_EXTERNAL_VREF           5000
-#define ADC_WRAPPER_EXTERNAL_VREF_CROSSVAL  3300
+#define ADC_WRAPPER_EXTERNAL_VREF_CROSSVAL  3000
 /*---------------------------------------------------------------------------*/
 #define ANALOG_GROVE_LIGHT                  0x01
 #define ANALOG_PHIDGET_ROTATION_1109        0x02
diff --git a/platform/zoul/dev/pm10-sensor.h b/platform/zoul/dev/pm10-sensor.h
index d43256e44..07f7811c1 100644
--- a/platform/zoul/dev/pm10-sensor.h
+++ b/platform/zoul/dev/pm10-sensor.h
@@ -52,7 +52,7 @@
 #define PM10_SENSOR                  "PM10 Sensor"
 #define PM10_SENSOR_PULSE_DELAY      280
 #define PM10_EXTERNAL_VREF           5000
-#define PM10_EXTERNAL_VREF_CROSSVAL  3300
+#define PM10_EXTERNAL_VREF_CROSSVAL  3000
 /* -------------------------------------------------------------------------- */
 #ifdef PM10_SENSOR_CONF_CTRL_PIN
 #define PM10_SENSOR_CTRL_PIN         PM10_SENSOR_CONF_CTRL_PIN