diff --git a/Core/Drivers/ANPI_AnalogPortsIn.c b/Core/Drivers/ANPI_AnalogPortsIn.c
index 8d3077c..92daa34 100644
--- a/Core/Drivers/ANPI_AnalogPortsIn.c
+++ b/Core/Drivers/ANPI_AnalogPortsIn.c
@@ -95,6 +95,8 @@ LOCAL osThreadId_t        m_pstThreadID       = NULL;
 LOCAL osEventFlagsId_t    m_pstEventID  		  = NULL;
 LOCAL osMutexId_t         m_pstMutexID        = NULL;
 
+LOCAL FLOAT flRefVoltage = INT_ADC_REF;
+
 //=================================================================================================
 // Section:       LOCAL CONSTANTS
 // Description:   Definition of local constants (visible by this module only).
@@ -198,6 +200,17 @@ BOOL ANPI_boInitializeModule( VOID )
   return( boOK );
 }
 
+//-------------------------------------------------------------------------------------------------
+// Function:      ANPI_vSetRefVoltage
+// Description:   Sets the Reference Voltage for calculating the Voltage
+// Parameters:    FLOAT flVoltage -> The Ref Voltage measured with an DMM for example
+// Returns:       None
+//-------------------------------------------------------------------------------------------------
+VOID ANPI_vSetRefVoltage( FLOAT flVoltage )
+{
+  flRefVoltage = flVoltage;
+}
+
 //-------------------------------------------------------------------------------------------------
 // Function:      ANPI_vTask
 // Description:   ANPI_vTask
@@ -234,7 +247,7 @@ VOID vTask( PVOID arg )
     // multiply conversion factor and add the offset
     for( U16 u16Cnt = 0; u16Cnt < ANPI_eInNumberOfInputs; u16Cnt++ )
     {
-      flUadc = (FLOAT)au32ADCRawData[u16Cnt] / OVERSAMPLING_DIVISOR / ADC_RES * INT_ADC_REF;
+      flUadc = (FLOAT)au32ADCRawData[u16Cnt] / OVERSAMPLING_DIVISOR / ADC_RES * flRefVoltage;
       aflValues[u16Cnt] = flUadc * m_aflConversionFactor[u16Cnt] - m_aflOffset[u16Cnt];
     }
 
diff --git a/Core/Drivers/ANPI_AnalogPortsIn.h b/Core/Drivers/ANPI_AnalogPortsIn.h
index 3f6ff74..1a8673e 100644
--- a/Core/Drivers/ANPI_AnalogPortsIn.h
+++ b/Core/Drivers/ANPI_AnalogPortsIn.h
@@ -94,6 +94,7 @@ typedef enum
 //=================================================================================================
 
 BOOL ANPI_boInitializeModule( VOID );
+VOID ANPI_vSetRefVoltage( FLOAT flVoltage );
 
 #ifdef __cplusplus
 }
diff --git a/Core/Drivers/ANPO_AnalogPortsOut.c b/Core/Drivers/ANPO_AnalogPortsOut.c
index 4c7f9db..44333c1 100644
--- a/Core/Drivers/ANPO_AnalogPortsOut.c
+++ b/Core/Drivers/ANPO_AnalogPortsOut.c
@@ -45,7 +45,7 @@
 // Description:   Definition of local constants (visible by this module only).
 //=================================================================================================
 
-
+#define INT_DAC_REF    (3.3f)// int. reference voltage for conversion
 
 //=================================================================================================
 // Section:       MACROS
@@ -75,6 +75,7 @@
 // Description:   Definition of local variables (visible by this module only).
 //=================================================================================================
 
+LOCAL FLOAT flRefVoltage = INT_DAC_REF;
 
 //=================================================================================================
 // Section:       LOCAL CONSTANTS
@@ -87,7 +88,7 @@
 // Description:   Definition of local functions (visible by this module only).
 //=================================================================================================
 
-U32 u32ConvertVoltagetoRaw( FLOAT Voltage );
+U32 u32ConvertVoltagetoRaw( FLOAT flVoltage );
 
 //=================================================================================================
 // Section:       EXTERNAL FUNCTIONS
@@ -124,6 +125,17 @@ BOOL ANPO_boInitializeModule( VOID )
   return( boOK );
 }
 
+//-------------------------------------------------------------------------------------------------
+// Function:      ANPO_vSetRefVoltage
+// Description:   Sets the Reference Voltage for calculating the Voltage
+// Parameters:    FLOAT flVoltage -> The Ref Voltage measured with an DMM for example
+// Returns:       None
+//-------------------------------------------------------------------------------------------------
+VOID ANPO_vSetRefVoltage( FLOAT flVoltage )
+{
+  flRefVoltage = flVoltage;
+}
+
 //=================================================================================================
 // Section:       LOCAL FUNCTIONS
 // Descriptionn:  Definition (implementation) of local functions.
@@ -135,10 +147,10 @@ BOOL ANPO_boInitializeModule( VOID )
 // Parameters:    FLOAT Voltage
 // Returns:       Boolean, TRUE if successful
 //-------------------------------------------------------------------------------------------------
-BOOL ANPO_boSetVoltage( FLOAT Voltage ){
+BOOL ANPO_boSetVoltage( FLOAT flVoltage ){
 	BOOL boOK = TRUE;
 	
-	U32 u32RawData = u32ConvertVoltagetoRaw( Voltage );
+	U32 u32RawData = u32ConvertVoltagetoRaw( flVoltage );
 	
 	boOK &= HAL_DAC_SetValue( &hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R, u32RawData );
 	
@@ -151,10 +163,10 @@ BOOL ANPO_boSetVoltage( FLOAT Voltage ){
 // Parameters:    FLOAT Voltage
 // Returns:       U32
 //-------------------------------------------------------------------------------------------------
-U32 u32ConvertVoltagetoRaw( FLOAT Voltage ){
+U32 u32ConvertVoltagetoRaw( FLOAT flVoltage ){
 	U32 RawData;
 	
-	RawData = Voltage * 4095 / 3.3;
+	RawData = flVoltage * 4095 / flRefVoltage;
 	
 	return RawData;
 }
diff --git a/Core/Drivers/ANPO_AnalogPortsOut.h b/Core/Drivers/ANPO_AnalogPortsOut.h
index 2663ef2..8ff9235 100644
--- a/Core/Drivers/ANPO_AnalogPortsOut.h
+++ b/Core/Drivers/ANPO_AnalogPortsOut.h
@@ -87,7 +87,8 @@ typedef enum
 //=================================================================================================
 
 BOOL ANPO_boInitializeModule( VOID );
-BOOL ANPO_boSetVoltage( FLOAT Voltage );
+BOOL ANPO_boSetVoltage( FLOAT flVoltage );
+VOID ANPO_vSetRefVoltage( FLOAT flVoltage );
 
 #ifdef __cplusplus
 }