Brief Overview of Thermistor Sensors and their Applications in Engineering & Medicine Sachin Mehta Reno Nevada

1. Thermistor Sensors
Written By: Sachin Mehta
University of Nevada, Reno
The sensors that are used in the health system can come in all various shapes, sizes, and forms.
Some are made to simply measure the temperature of one’s self, while others are manufactured
in order to ensure other things take place. One important type of sensor that is used in
healthcare a great deal is termed the thermistor. These temperature sensing elements are
made of semiconductor material that have been sintered in order to display large changes in
resistance in proportion to small changes in temperature. These thermistors have a wide range
of applications from use in dialysis machines, in neonatal care machines, pressure sensors, and
anesthesia machines. For example, during kidney dialysis a patient’s blood is removed from the
body through a machine and then is artificially filtered and treated/returned to the patient’s
body. However, it is important that we ensure that the patient’s blood is reheated to body
temperature before it returns to the patient’s body circulation. Fig. 1 displays some common
NTC thermistors that are currently being used in various products worldwide.
Fig. 1: Common Types of Thermistor Used in Production of Different Equipment
Tiny NTC Thermistors are also heavily used in cardiac diagnostics such as thermo-dilution
catheters. The thermistors are placed near the tips of the catheters and are hermetically sealed
in glass and have alloy leads. In addition, disposable hypodermic needle also implement and use
thermistor sensors, again as to help in temperature modification. They are extremely critical
during open heart surgery when they are inserted into the myocardium muscle and then used to
monitor temperature. These hypodermic needle probes with small thermistor beads or chips
are inserted into targeted anatomical sites for temperature measurement and are particularly
suited for cancer treatment as well as cancer research—particularly for brain tumors. In
reference to incubators, NTC thermistors monitor, again, the temperature—but also the air
circulation within the incubator itself. These thermistors—placed on probes and patches
sometimes even help and assist physicians with monitoring the skin temperatures of young

2. Thermistor Sensors
Written By: Sachin Mehta
University of Nevada, Reno
babies and premature infants. It is also common for physicians to use various micro circuit
assemblies that are specifically designed for oral and/or rectal patient temperature monitoring.
Thermistors are very important tools in the design and implementation of many biomedical
applications and products. In addition to NTC thermistors, there are also positive
resistance/temperature coefficient thermistors—however most commonly used in the medical
field and in healthcare devices are the NTC thermistors that were discussed previously in great
detail. It is important to note some key characteristics of these NTC thermistors such as the fact
that they are mainly manufactured from the oxides of transition metals. Fig. 2 below depicts
which the transition metals on the periodic table of elements.
Figure 2: Periodic Table Showing the Transition Metals
These transition metal oxides are materials that can have unusual, but very useful electronic and
magnetic properties. These oxides are widely used in various catalytic processes, but more
importantly are used in thermistors. NTC thermistors can operate in the temperature range
from -196 ° C all the way to 1000 ° C and are very sensitive to changes in electrical power input.
As discussed, the applications of thermistors are widespread and have very useful properties
that make them ideal in biomedical and healthcare systems, products, and devices.