Thermistor For Body Temperature Measurement

The temperature measurement of the surface of the body can be accomplished using different sensors.

Thermistor for body temperature measurement. Since the human skin acts as a thermal insulator the temperature of the skin isn t an accurate representation of actual body temperature. For this reason for most low cost temperature measurement ntc thermistors are preferred. The variable t is the ambient temperature in kelvin t0 is usually room temperature also in kelvin 25 c 298 15k b is the beta constant r is the thermistor resistance at the ambient temperature same as rt above and r0 is the thermistor resistance at temperature t0. Te connectivity te manufactures ntc negative thermal coefficient thermistors thermopiles and digital temperature sensors to support the wide range of accuracy packaging and performance conditions amongst the different.

Convert the temperature values to kelvins and invert. The thermistor measures the cold junction temperature of the thermopile and both the thermopile and thermistor measurements are used to calculate the body temperature. It is relatively easy to calibrate your own response curves if you have an accurate temperature measurement standard. This makes the ptc thermistor a little harder to interface with.

The temperature measurement of the surface of the body can be accomplished using different sensor technologies. The typical operating temperature range of a thermistor is 55 c to 150 c though some glass body thermistors have a maximal operating temperature of 300 c. The adt7422 has an accuracy of 0 1 c over a temperature range of 25 c to 50 c. Thermistor linearization curves.

Types of sensors like ntc negative thermal coefficient thermistors thermopiles and digital temperature sensors. Temple and forehead type thermometers use the same technology to measure infrared radiation as ear type thermometers they just measure it from a different location on the body. Avoid dewing and condensation unless thermistor is specified for these conditions. Perfluoropolyethers such as galden.

Measurement purposes checking the specified resistance vs. However ptc thermistors have a sort of tipping point and greatly change the resistance at some temperature. Temperature the component must not be immersed in water but in suitable liquids e g. Thermistors differ from resistance temperature detectors rtds in that the material used in a thermistor is generally a ceramic or polymer while rtds use pure metals.

This temperature range is centered around the typical human body temperature of 38 c making the adt7422 ideal for accurate vital signs monitoring. The silicone oil provides a very uniform temperature so many devices can be calibrated in a single cycle.