Introduction to sensors and Temperature Sensors
First, we’re going through the basics, what are sensors? Sensors are
devices that detect events or changes in the physical environment and
provide a corresponding output. In other words, they convert physical
parameters such as temperature, pressure, etc. into signals.
In this presentation, we will look into details of a specific type of sensor,
temperature sensors. Temperature sensors are sensors that measure the temperature
of its environment and convert it into signal, sound simple enough?
However, despite that, temperature sensors have a much more difficult history of
development than other types of sensors. This is because unlike other physical parameter
like weight or length, temperature at first can only be “measure” through indirect method,
observing its impact on its surroundings.
Starting from the beginning …
The first device that can be considered as a temperature sensor was created
by Galileo in 1592, which used air contraction to indicate cooling. However, it
is because the device’s dependent on air pressure to measure, it was deemed unreliable.
In 1612, Santorio Santorii invented the first liquid thermometer, using the
expansion of water and a scale to mark the changes in temperature.
The bimetallic temperature sensor was invented by John Harrison and,
despite its low accuracy, was widely used during the 19 th century in various
applications due to it being simple and cost-effective.
By 1821, the German physicist Seebeck discovered the Seebeck effect that
turns temperature into an electrical signal and invented the thermocouple
sensor. This is an important discovery, and it made a huge contribution to
the industrial revolution at the time and served as a foundation for later modern
temperature sensors.
Now that we have a brief image of this type of sensor, moving on to its application
Temperature sensors play a critical role in various industries and homes.
In industrial settings, temperature sensors are essential. They monitor and control
processes to ensure the production goes as planned and to prevent damage or accidents. A
prime example is the use of temperature sensors in Steel Production.
In the Blast Furnaces, Iron ores are melted at high temperatures to produce molten iron.
Temperature sensors, such as thermocouples, measure the molten iron's temperature to
ensure proper chemical reactions.
Underheating, the iron may not fully melt, resulting in impurities in the final product.
Overheating, production can damage furnace linings.
Another example is in home applications with the smart thermostats… Smart thermostats
are usually installed in major room like the living room or bedroom. It will use its built-in
temperature sensors to continuously measure ambient room temperatures and adjust the
heating or cooling systems automatically
Types of Temperature Sensors
Going for more details, we will briefly walk you through some type of temperature sensors
used…
First, we have the RTD… RTD stands for Resistance Temperature Detectors, and it consist of
a length of fine wire wrapped around a heat-resistant ceramic or glass core.
The RTD wire needs to be made purely from 1 material, typically platinum, nickel, or
copper which have an “accurate” relationship between temperature and resistance. This
relationship can be used to provide an indication of temperature. However, due to its rather
“simple” design, the RTD is fragile and was often housed in protective probes.
The RTDs are known for its higher accuracy and repeatability, replacing thermocouples in
industrial applications below 600 °C
Next, we have thermocouple… The thermocouple is an electrical device consisting of two
different electrical conductors, forming an electrical junction. A thermocouple produces a
temperature-dependent voltage as a result of the Seebeck effect, and this voltage can be
interpreted to measure temperature. Commercial thermocouples are inexpensive,
interchangeable, are supplied with standard connectors, and can measure a wide range of
temperatures, making it very common.
