56
F. Firouzi et al.
– Thermocouple Sensors – They are made of two different metal conductors
(e.g., chrome and alumel) that have dissimilar thermal conduction characteristics. The conductors are welded at one end so to generate temperaturedependent voltage through a thermoelectric effect.
– Resistance Temperature Detector (RTD) – The level of resistance changes
based on the temperature in pure material, such as platinum, nickel, and
copper. RTD sensors are based on this phenomenon to measure temperature.
Due to their stability, precision, and repeatability, RTD sensors are often used
to monitor laboratory or industrial process temperatures.
– Thermistors – They employ semiconductor elements to measure temperature.
Similar to the RTD sensors, the level of resistance in thermistors changes
based on temperature. These sensors exhibit a more nonlinear resistance
behavior as the temperature varies.
• Flow Sensors – These sensors can measure flow rate and the total volume
of gases or liquids in pipes or systems. Such capability is vital for practical
everyday applications such as brewing machines as well as scientific endeavors
like monitoring the flow of highly pure acids. An example of how important
flow monitoring sensors are can be found in the 2014 Flint, Michigan, United
States, water crisis. The city of Flint switched its water sourcing from the
Great Lakes through Detroit Water to obtaining water through the Flint River.
However, officials failed to identify high levels of lead, a very serious danger
to public health, in the water source. The very acidic water of the Flint River
leeched lead out of the pipes and passed it into the water, resulting in very high
levels of heavy metals in the water. Thousands of children who consumed or
were exposed to the contaminated water experienced severe health problems. In
2016, criminal charges were filed by Michigan’s attorney general against three
individuals regarding the crisis.
• Level Sensors – These sensors measure fluid levels constantly or at certain points.
Level sensors can be used in many ways and are capable of measuring contained
fluids or elements in a natural setting such as oil levels at an oil rig site. For
example, ultrasonic sensors do not require direct contact and are often utilized in
measuring viscous liquids or bulky solid materials. These sensors are also useful
in controlling pumps and measuring open channel flow in water treatment plants.
Capacitance level sensors measure the existence of liquids and solids using radio
frequency signals in the circuit.
• Imaging Sensors – This sensor captures and transforms the changing attenuation
of waves into signals. Imaging sensors are often found in medical imaging
machinery, digital cameras, and night vision paraphernalia.
• Noise Sensors – High noise levels from machinery, aircraft, trains, construction,
or loud music can cause harm to both humans (i.e., cardiovascular or hearing
damage) and animals. Regulatory entities have begun employing noise sensors in
order to better measure noise pollution and disturbances that may cause harm. For
instance, ambient noise sensors constantly measure environmental noise levels
and transmit an electronic signal to an ambient noise system when the noise level
F. Firouzi et al.
– Thermocouple Sensors – They are made of two different metal conductors
(e.g., chrome and alumel) that have dissimilar thermal conduction characteristics. The conductors are welded at one end so to generate temperaturedependent voltage through a thermoelectric effect.
– Resistance Temperature Detector (RTD) – The level of resistance changes
based on the temperature in pure material, such as platinum, nickel, and
copper. RTD sensors are based on this phenomenon to measure temperature.
Due to their stability, precision, and repeatability, RTD sensors are often used
to monitor laboratory or industrial process temperatures.
– Thermistors – They employ semiconductor elements to measure temperature.
Similar to the RTD sensors, the level of resistance in thermistors changes
based on temperature. These sensors exhibit a more nonlinear resistance
behavior as the temperature varies.
• Flow Sensors – These sensors can measure flow rate and the total volume
of gases or liquids in pipes or systems. Such capability is vital for practical
everyday applications such as brewing machines as well as scientific endeavors
like monitoring the flow of highly pure acids. An example of how important
flow monitoring sensors are can be found in the 2014 Flint, Michigan, United
States, water crisis. The city of Flint switched its water sourcing from the
Great Lakes through Detroit Water to obtaining water through the Flint River.
However, officials failed to identify high levels of lead, a very serious danger
to public health, in the water source. The very acidic water of the Flint River
leeched lead out of the pipes and passed it into the water, resulting in very high
levels of heavy metals in the water. Thousands of children who consumed or
were exposed to the contaminated water experienced severe health problems. In
2016, criminal charges were filed by Michigan’s attorney general against three
individuals regarding the crisis.
• Level Sensors – These sensors measure fluid levels constantly or at certain points.
Level sensors can be used in many ways and are capable of measuring contained
fluids or elements in a natural setting such as oil levels at an oil rig site. For
example, ultrasonic sensors do not require direct contact and are often utilized in
measuring viscous liquids or bulky solid materials. These sensors are also useful
in controlling pumps and measuring open channel flow in water treatment plants.
Capacitance level sensors measure the existence of liquids and solids using radio
frequency signals in the circuit.
• Imaging Sensors – This sensor captures and transforms the changing attenuation
of waves into signals. Imaging sensors are often found in medical imaging
machinery, digital cameras, and night vision paraphernalia.
• Noise Sensors – High noise levels from machinery, aircraft, trains, construction,
or loud music can cause harm to both humans (i.e., cardiovascular or hearing
damage) and animals. Regulatory entities have begun employing noise sensors in
order to better measure noise pollution and disturbances that may cause harm. For
instance, ambient noise sensors constantly measure environmental noise levels
and transmit an electronic signal to an ambient noise system when the noise level