Industrial Automation
Coshgun Humbatov
630.19E
TOPIC
Level Sensors
What is level sensor?
Level sensor is a device
that is designed to
monitor, maintain, and
measure liquid and
sometimes solid levels.
Level sensors
Level sensors are used
primarily in the manufacturing
and automotive industries.
Level sensors are useful devices that are used to detect the level of
substances such as liquids, powders.
There is a wide range of level sensors and they are all used in
different industries.
Classifications of level sensors
There are two main classifications for level sensors:
1.Point level sensors
2.Continuous level sensors
Point level measurement shows when a product is present at a
certain point.
Continuous level measuring shows the continuous level of a
product as it rises and falls.
The sensors for point level measurement are:
– Capacitance
– Optical
– Conductivity
– Vibrating (Tuning fork)
– Float Switch
The sensors for continuous level measurement are:
– Ultrasonic
– Radar (Microwave)
Level sensors can be divided into:
Invasive
Non-contact sensors
Invasive sensors make direct contact with the substance
they are measuring.
Non-contact sensors use sound or microwaves.
1. Capacitance Level Sensor
– Small
– Less expensive than
other sensors
– Invasive to product
– Accurate
– Have no moving parts
2. Optical Level Sensor
– These sensors have no moving parts
– They are not affected by high pressure or
temperature
– Used in liquid applications
– Small size
Optical sensors work by
converting light rays into
electrical signals
3. Conductivity (Resistance) Level Sensor
A conductivity or resistance sensor uses a probe to read
conductivity. The probe has a pair of electrodes.
The advantages of conductivity level sensor are:
– no moving parts
– low cost
– easy to use
The disadvantages are:
– They are invasive (meaning they must touch the product
being sensed)
– They only sense conductive liquids
4. Vibrating (Tuning Fork) Level Sensor
– Cost effective and compact
– Invasive to the product,
– Easy to install
– Essentially maintenance-free
Mining, food and beverage, and chemical processing
industries use these sensors for their applications.
5. Float Switch
Float switches use a float, a device that will raise or
lower when a product is applied or removed.
The advantages of a float switch are:
– non powered device
– provide a direct indication
– inexpensive
The disadvantages are:
– invasive to the product
– have moving parts
– can be large in size
Continuous Level Measurement Sensors
1. Ultrasonic Level Sensor
• Ultrasonic level sensors work by emitting and receiving ultrasonic
waves.
The advantages :
– have no moving parts
– compact and reliable
– Non-invasive (Non-contact)
– Self-cleaning because of the vibrations they give off
The disadvantages :
– They can be expensive
– In some situations, the environment can have a negative effect on them
2. Radar Level Sensor
• These sensors transmit microwaves by an antenna on the
radar sensor.
The advantages of radar sensors are that:
– they are not affected by temperature, pressure
– they can measure liquids, pastes, powders, and solids
– they are very accurate and require no calibration
– they are non-invasive
The disadvantages of radar sensors are that:
– expensive
– a limited detection range
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