Thermocouple and RTD technology is the workhorse of the temperature measurement industry. It has been refined and extended to cover a broad range of temperature measurement needs. However, it is well documented, though not widely advertised, that these measurement devices experience "drift" or de-calibration while in service. For various reasons the sensor output can "drift" away from representing the true temperature. The magnitude of the drift depends on sensor type, construction, installation and process conditions. The real problem is that there has been no way to tell when drift begins or to determine its magnitude, or even its direction. Now, Dynamically Self-Validating Sensors have been invented that eliminate unreliable readings and warn in advance of the onset of drift. In this paper, the technology of Self-Validating Sensors is explained and data is provided showing the performance of a Self-Validating sensor.