Medical thermometer and displaying temperature became available, electronic thermometers (often called "digital", because they display numeric values) have been used. Many display readings to great precision (0.1 °C or 0.2 °F, sometimes half that), but this should not be taken as a guarantee of accuracy: specified accuracy must be checked in documentation and maintained by periodical recalibration. A typical inexpensive electronic ear thermometer for home use has a displayed resolution of 0.1 °C, but a stated accuracy within ±0.2 °C (±0.35 °F) when new. The first electronic clinical thermometer, invented in 1954, used a flexible probe that contained a Carboloy thermistor. Types
Thermometer the principles of the thermometer were known to Greek philosophers of two thousand years ago. The modern thermometer gradually evolved from the thermoscope with the addition of a scale in the early 17th century and standardisation through the 17th and 18th centuries. While an individual thermometer is able to measure degrees of hotness, the readings on two thermometers cannot be compared unless they conform to an agreed scale. Today there is an absolute thermodynamic temperature scale. Internationally agreed temperature scales are designed to approximate this closely, based on fixed points and interpolating thermometers. The most recent official temperature scale is