Sensor with digital signature of data relating to sensor

A sensor has codes useful for a monitor which can be authenticated as accurate. The sensor produces a signal corresponding to a measured physiological characteristic and provides codes which can be assured of being accurate and authentic when used by a monitor. A memory associated with the sensor stores both data relating to the sensor and a digital signature. The digital signature authenticates the quality of the code by ensuring it was generated by an entity having predetermined quality controls, and ensure the code is accurate.