def getValue(self,convert=False):
        if convert and conversion.convertable(self.value):
#            print 'convert', self.value,convert
            r = conversion.convertTo(self.units,self.value)
            return r[1]
        else:
            return self.value
 def getUnits(self,convert=False):
     if convert:
         r = conversion.convertTo(self.units,1)
         return r[0]
     else:
         return self.units