<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def readTempC(self):
 		"""Read sensor and return its value in degrees celsius."""

		# Read temperature register value.
		t = self._device.readU16BE(MCP9808_REG_AMBIENT_TEMP)
		self._logger.debug('Raw ambient temp register value: 0x{0:04X}'.format(t & 0xFFFF))
		# Scale and convert to signed value.
		temp = (t & 0x0FFF) / 16.0
		if t & 0x1000:
			temp -= 256.0
		return temp