Added temperature offset/gain settings for AD595.

Marlin/Configuration.h

 #define HEATER_2_MAXTEMP 275
 #define BED_MAXTEMP 150
 
+//These defines help to calibrate the AD595 sensor in case you get wrong temperature measurements.
+//The measured temperature is defined as "actualTemp = (measuredTemp * TEMP_SENSOR_AD595_GAIN) + TEMP_SENSOR_AD595_OFFSET"
+#define TEMP_SENSOR_AD595_OFFSET 0.0
+#define TEMP_SENSOR_AD595_GAIN   1.0
+
+
 // PID settings:
 // Comment the following line to disable PID and enable bang-bang.
 #define PIDTEMP

Marlin/temperature.cpp

 
     return (1023 * OVERSAMPLENR) - raw;
   }
-  return celsius * (1024.0 / (5.0 * 100.0) ) * OVERSAMPLENR;
+  return ((celsius-TEMP_SENSOR_AD595_OFFSET)/TEMP_SENSOR_AD595_GAIN) * (1024.0 / (5.0 * 100.0) ) * OVERSAMPLENR;
 }
 
 // Takes bed temperature value as input and returns corresponding raw value. 
 
     return (1023 * OVERSAMPLENR) - raw;
 #elif defined BED_USES_AD595
-    return lround(celsius * (1024.0 * OVERSAMPLENR/ (5.0 * 100.0) ) );
+    return lround(((celsius-TEMP_SENSOR_AD595_OFFSET)/TEMP_SENSOR_AD595_GAIN) * (1024.0 * OVERSAMPLENR/ (5.0 * 100.0) ) );
 #else
     #warning No heater-type defined for the bed.
     return 0;
 
     return celsius;
   }
-  return raw * ((5.0 * 100.0) / 1024.0) / OVERSAMPLENR;
+  return ((raw * ((5.0 * 100.0) / 1024.0) / OVERSAMPLENR) * TEMP_SENSOR_AD595_GAIN) + TEMP_SENSOR_AD595_OFFSET;
 }
 
 // Derived from RepRap FiveD extruder::getTemperature()
     return celsius;
     
   #elif defined BED_USES_AD595
-    return raw * ((5.0 * 100.0) / 1024.0) / OVERSAMPLENR;
+    return ((raw * ((5.0 * 100.0) / 1024.0) / OVERSAMPLENR) * TEMP_SENSOR_AD595_GAIN) + TEMP_SENSOR_AD595_OFFSET;
   #else
     #warning No heater-type defined for the bed.
   #endif