diff --git a/lppinstru/dlp_temp.py b/lppinstru/dlp_temp.py
--- a/lppinstru/dlp_temp.py
+++ b/lppinstru/dlp_temp.py
@@ -43,6 +43,12 @@ class dlp_temp(object):
         self.i=0
         self.__port=serial.Serial(port,timeout=0.5)
 
+    def _byte_to_int(self,byte):
+        if byte >= 128:
+            return byte-256
+        else:
+            return byte
+
     def ping(self):
         self.__port.write(b"P")
         return b'Q' == self.__port.read(1)
@@ -51,7 +57,7 @@ class dlp_temp(object):
         if index < 3:
             self.__port.write(self.sensors.get(index))
             dat=self.__port.read(9)
-            test=( int(ord(dat[0])) + (int(ord(dat[1]))*256) )
+            test=( self._byte_to_int(dat[0]) + (self._byte_to_int(dat[1])*256) )
             temp=float(test)*0.0625
             return temp #(temp-32.0)/1.8
         raise UserWarning("Parameter out of bound")
@@ -60,7 +66,7 @@ class dlp_temp(object):
         if index < 3:
             self.__port.write(self.aninputs.get(index))
             dat=self.__port.read(2)
-            test=( int(ord(dat[0])) + (int(ord(dat[1]))*256) )
+            test=( self._byte_to_int(dat[0]) + (self._byte_to_int(dat[1])*256) )
             val=float(test)/512.0
             return val
         raise UserWarning("Parameter out of bound")