THERMISTORS AND THEIR USE IN ANESTHESIA

🔻A #thermistor is a temperature-sensitive resistor whose resistance changes with temperature.

🔻Most temperature-sensitive resistors are constructed from a semiconductor material (carefully chosen metal oxides) and the resistance increases with a fall in temperature (they have a negative temperature coefficient)

🔻So they are known as negative thermal conductivity (NTC) thermistors.

🔻A Wheatstone bridge circuit is used to measure the resistance accurately.

🔻The main disadvantage of thermistors is the non-linear resistance versus temperature characteristic, although this can be compensated for using an appropriate calibration equation programmed into an electronic measurement system.

🔻Thermistors remain highly popular due to their cost, miniature size and convenience.

🔻Thermistor probes are commonly placed in the nasopharynx, oesophagus, rectum or bladder (integrated with a urinary catheter).

🔻They have excellent accuracy and their small mass means that there is a quick response to variations in temperature.

🔻True or False? 'A thermistor comprises a junction of dissimilar metals'

🔻Answer: False. Dissimilar junctional metals are thermocouples