What are the level switch and level meter?
What are level switches, level meters and level sensors? Where are they used?
This page explains how level switches, level meters, and level sensors are used in various locations including industrial factories and plants.
What are level switch and level meter?
Importance of level switches and level meters
Introduction of level sensors with various operating principles
What are level switch and level meter?
Factories, plants, various equipment, rivers, and utility water tanks all need to monitor and control the levels and remaining volume of liquids,
powder, or granulated materials. Level switches and level meters detect and measure materials such as liquids, powder, and granulated materials in
tanks, vessels, and plumbing.
The switch captures the electrical difference
between empty and full of material to detect the
level. When material is empty, electrical status
of detecting electrode and grounding electrode
is: resistance (Ro) is infinite, and capacitance
(Co) will be specific capacitance value
determined by installation status.
What is level switch?
A level switch is a sensor that detects the presence of liquids, powder, or granulated materials at a specific location.(It is also referred to as level
sensor) For example, when a tank is supplied with liquid, it overflow.In order to prevent overflows, a level switch is installed near the top of the
tank. When the liquid touches the level switch, it outputs a signal to keep the liquid from overflowing the tank. (To detect that a tank is filled with
material is referred to full detection, or upper limit detection.) On the other hand, when the liquid level drops as the liquid is discharged, a level
switch is used to prevent completely draining the tank. This is referred to as an empty detection or lower limit detection.
What is the level meter?
Different from level switches, level meters these devices continuously measure the volume of liquid, powder, or granulated materials. (This is also
referred to continuous level meter, liquid meter, or powder meter.) Although a level switch can detect the presence of material at a certain point, a
level meter outputs a reading of the total liquid volume in a tank, usually from 0 to 100%. So, a level meter can monitor and control the volume in
greater detail than a level switch. The level meter usually outputs its reading as a small current of 4 to 20mA. (4mA represents 0%, 20mA
represents 100%, and 12mA represents 50%,)
Importance of level switches and level meters
As production facilities put more emphasis on energy saving, they are using lots of various types of sensors.
Among these types of sensors, level sensors are used in harsh conditions with extreme temperatures, pressures, vibration, and surrounding
environments. The objects measured by level sensors are greatly diversified. Under these conditions, level sensors are required to be extremely
reliable. Our level sensing equipment meets these requirements. They are manufactured using lots of experience and technical skill. We are proud
of their quality and reliability.
Introduction of level sensors with various operating principles
However, you cannot detect substances if you do not select optimum sensor depending on substance to detect (liquid, or powder) and detecting
conditions (use temperature, etc.).
This page describes which method and which product (level switch or liquid meter) is best for the substances and conditions you want to detect,
taking some typical examples.
Detecting liquids (liquid level meter, water level meter)
Typical examples for measuring and detecting
liquids are as follows:
< level switch >
1. Float type
: Uses a float that rests at the water level
2. Electrode water level switch
: Uses the principle that current flows
through the electrodes
3. Cable float type
: Uses a float that rests at the water level
4. Capacitance type
: Uses the dielectric constant of the liquid
< Liquid level meter / water level meter
>
5. Ultrasonic wave type
: Uses reflection of an ultrasonic wave
6. Pressure type (Submersible hydrostatic type)
: Uses pressure (water pressure) of the liquid
7. Guided radar type
: Uses the principle of micropulse reflection
8. Capacitance type
: Uses the dielectric constant of the liquid
And so on.
Each type has advantages and disadvantages. Therefore, we must choose the detection method depending on the liquid type and conditions of use.
Features of each method and precautions for selection are described below.
Switch
1. Float type liquid
2. Electrode type
3. Cable float type
4. Capacitance type
level switch
liquid level switch
liquid level switch
liquid level switch
A float moves up
When the
The float moves up
Detects and
and down due to
buoyancy. A reed
conductive liquid
touches between
and down
according to the
measures the
difference between
a material’s
Method
switch is actuated
the electrodes, a
principle of
by a magnet in the
current flows
buoyancy, and the
specific
float, and outputs a
detection signal
through the
electrodes, detects
it, and outputs a
detection signal.
magnet inside the
float activates the
reed switch to
output a detection
signal.
capacitance
dielectric constant
and the present
liquid’s dielectric
constant to detect
the liquid level and
output.
Low cost and easy
to use.
Can be used at low
cost. The length of
the electrode can be
changed by the
customer.
Low cost and easy
to use.
Can detect and
measure under hard
conditions of high
temperature and
high pressure.It can
also measure
highly viscous
liquid.
Disadvantages
May not be used
for viscous liquid,
liquids of low
specific gravity, or
in high temperature
or high pressure
situations
Cannot be used for
fully insulating
liquids. The size of
the connection is
large. Weak to
adhesion.
may not be used in
highly viscous
liquids, light
specific densities,
high temperature
and high pressure
places.
Cannot measure
when the dielectric
constant of the
liquid changes.
Related links
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information
Special examples
of use
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information
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information
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information
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of use
7. Guided radar
type liquid level
meter
8. Capacitance type
liquid level switch
Principle
Advantages
See here for liquid and water level switched with other methods
Liquid level meter / water level meter
Method
5. Ultrasonic type
liquid type level
meter
6. Pressure type
liquid level
meter(Submersible
hydrostatic type)
Principle
Emits an ultrasonic
wave and receives
it after it is
Install it in the
lowest position of a
tank and it detects
Emits an
microwave and
receives it after it is
Detects and
measures the
difference between
reflected off the
liquid surface.
liquid pressure and
outputs the results.
reflected off the
liquid surface.
a material’s
specific
Then it converts the
time difference
Then it converts the
time difference
capacitance
dielectric constant
between sending
and receiving the
wave to a
between sending
and receiving the
wave to a
and the present
liquid’s dielectric
constant to detect
measuring signal
and outputs the
measuring signal
and outputs the
the liquid level and
output.
data.
data.
Measure without
Easy to use.
contact material.
Easy to handle.
Advantages
Not affected by
Can detect and
environmental
changes. Supports
measure under hard
conditions of high
storage tanks and
large silos.
temperature and
high pressure.It can
also measure
highly viscous
liquid.
Disadvantages
Related links
Cannot be used in
May not measure at
Not suitable for
Cannot measure
vacuum.May not be
used under high
high temperature
and high pressure
small tanks and
narrow spaces. It
when the dielectric
constant of the
temperature, high
pressure, vapored,
dusty environment,
as difference may
be large.With a
continuous
may malfunction
due to bubbles. If
the permittivity is
liquid changes.
and obstacles.
indicating type, the
sensor shall be
low, it may not be
possible to
installed at lower
position of a tank
measure.
Product
information
Product
information
Production
information
Special examples
of use
See here for liquid and water level meters with other methods
Level switch and level meter for powder
Production
information
Special examples
of use
Typical examples for measuring and detecting
powder and granulated materials
< level switch >
1. Paddle type
: Uses the principle of slowing or stopping a
rotating vane
2. Vibration type
: Uses the principle of attenuation of a
vibrating bar
3. Capacitance type
: Uses the dielectric constant of the powder
4. Ultrasonic wave type
: Uses reflection of an ultrasonic wave
Each type has advantages and disadvantages. Therefore, we must choose the detection method depending on the liquid type and conditions of use.
Features of each method and precautions for selection are described below.
1. Paddle type
2. Vibration type
3. Capacitance type
4. Ultrasonic wave
(switch)
(switch)
(switch,
continuous)
type (switch,
continuous)
Method
Principle
Advantages
A shaft with a vane
A rod vibrates at a
Detects and
Emits an ultrasonic
at the end rotates.
When the vane
specific frequency.
When material
measures the
difference between
wave and receives
it after it is
touches material,
the vane stops
rotating and
touches the rod the
vibration is
attenuated. The unit
a material’s
specific
capacitance
reflected off the
liquid surface.
Then it converts the
outputs a detection
signal.
detects this
attenuation and
dielectric constant
and the air
time difference
between sending
outputs detection
signals.
dielectric constant
to detect a level
and receiving the
wave to a
and output it.
measuring signal
and outputs the
data.
Low cost and easy
Can detect even
Can detect and
Measure without
to use.
physical property is
changed.No need
measure under hard
conditions of high
contact material
for initial
adjustment and
maintenance.
temperature and
high pressure. Also
can measure
adhesive powder
and granulated
materials.
Disadvantages
Related links
As this is
mechanical type, it
Cannot be used in
locations with a lot
Cannot measure
levels if the
Cannot be used in
vacuum.May not be
may need
maintenance.
of external
vibration, at high
dielectric constant
of the material
used under high
temperature, high
Cannot be installed
at location with
temperatures, or
under high
changes
pressure, vapored,
dusty environment,
much vibration.
pressure.
Production
Production
Production
Production
information
Special examples
information
Special examples
information
Special examples
information
Special examples
of use
of use
of use
of use
Click here to see powder level meters using other methods
and obstacles.