Level Transducer
Level sensors are the devices which are used to detect the level of flowing substances such as
liquids, slurries, granular materials, and powders etc. Due to gravity, all these substances flow to
form a basic level in their physical boundaries. These flowing substances can have their boundary
either in the form of a container (vessel) or natural form like a river or a lake.
Level Measurement
Integral to process control in many industries, level measurement sensors fall into two main types.
Point level measurement sensors are used to mark a single discrete liquid height–a preset level
condition. Generally, this type of sensor functions as a high alarm, signaling an overfill condition,
or as a marker for a low alarm condition.
There are many ways to measure either point or continuous level. Point measurement technologies
include float switches, vibrating forks, capacitive sensors, and others. Continuous level technologies
include radar, ultrasonic, magnetostrictive, capacitive, float-and-tape, differential pressure, and
others.
Level Measurement Methods
The two major methods of level measurenment are:
1.Point Level sensors
• Point level sensors are devices that are capable of detecting the presence or absence of
almost any liquid media.
• These sensors are typically employed for processes where low or high levels need to be
detected.
• Generally, the most common applications requiring a point level sensor are divided into two
categories; leak detection – preventing costly damage to equipment or level measurement or
service interruption – preventing run dry or overspill situations.
• The technology performs similar to a switch to drive an action when the vessel or tank level
reaches above or below a specific threshold.
• The following are some examples of liquid level sensors that can work as point level
sensors:
1. Ultrasonic Liquid Level Sensors
2. Vertical Float Switches
3. Horizontal Float Switches
4. Optical Liquid Level Sensors
2.Continuous level sensors:
• In this method, continuous level sensors are employed which determine liquid level within a
given range instead of at a single point at anytime.
• These sensors usually indicate the correct amount of substance in the specified area.
• These sensors are extra sophisticated and capable enough to perform level monitoring for
the complete system.
• Usual applications that require a continuous level sensor are processes where high accuracy
is essential and where it is important to know the liquid level, such as inventory control or
process control and management.
• The following are examples of liquid level sensors that can work as continuous level
sensors:
1. Ultrasonic Liquid Level Sensors
2. Submersible Liquid Level Sensors
3. Optical Liquid Level Sensors
• Via this method an analog output is generated which directly correlates to the level in the
container.
Level Measurement Principle
Level devices operate under three main different principles:
1. The position (height) of the liquid surface
2. The pressure head
3. The weight of the material
