parameters: (self,value)
docstring: takes a string in the HP3456A format and returns a float value or None if not parseable
docstring_summary: takes a string in the HP3456A format and returns a float value or None if not parseable
docstring_tokens: takes a string in the HP3456A format and returns a float value or None if not parseable
function: def parse_value(self,value):
          """
          takes a string in the HP3456A format and returns a float value or None if not parseable
          """
          try:
              return float(value)
          except:
              return None
function_tokens: def parse_value ( self , value ) : try : return float ( value ) except : return None