The level sensor | KEYENCE America (2023)

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Detection Guide FL Series Pulse Level Sensor

The FL series is the industry's first lead pulse level sensor. New TriSense technology enables detection of any liquid while automatically adapting to the external environment (eg waves, foam, etc.) and probe condition (eg deposits).

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Stable detection at all times

The new "Sensing Guidance Pulse Method" enables the detection of liquids, taking into account obstacles in the area. This is achieved by automatically taking construction into account.

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Traditional problems eliminated

The FL series solves all the problems of conventional level sensors that lead to false detections. This helps avoid costly downtime from situations such as boil dry, tank overflow, or accidental dehydration.

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High Performance Digital Ultrasonic SensorsFW Series

FW series high performance digital ultrasonic sensors are super multi-reflective non-contact level switches that can perform stable detection of any target. They are not affected by the color, pattern, gloss, or transparency of surfaces, so they can be used on any target, including liquid levels, metal, and glass. The IP67 rated sensor heads have excellent environmental resistance and emit powerful ultrasonic waves that penetrate dust and dirt to detect work pieces. The newly registered A.W.S. (Active Wave Stabilizer) algorithm eliminates the influence of lens vibration or ambient light. The N.O.D. (Closest Object Detection) detects only the closest subject without being affected by background glare or shapes. This allows stable detection of any target in any installation environment.


It can be used for all kinds of goals.

The FW series easily detects metal, glass, liquid levels, or other objects that are difficult to detect with reflective photoelectric sensors. Additionally, detections are not affected by the color, pattern, or brightness of the target surface.

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High stability and reliability

A new algorithm A.W.S. (Active Wave Stabilizer)* stabilizes detection and prevents the influence of target vibration or external interference.

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Level sensors are instruments used to detect or measure the level of liquids or powders in tanks or containers. They are essentially subdivided into level switches and level measurement devices.
Level switches are sensors that detect the amount of material in a container at a specific point. One type of level switch detects the level based on contact sensors installed at the upper and lower limits of the level. Another type accurately detects the distance between the sensor head and the contents of the container. This type commonly uses ultrasonic waves from the inside near the top of the container.
Level gauges are instruments that continuously detect or measure the level from inside near the top of containers. Compared to level switches, they allow more precise management of the remaining quantity. They are also called continuous level gauges, liquid level gauges, or liquid level gauges.

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A: level indicator (continuous level indicator), B: level switch (for upper limit detection), C: level switch (for lower limit detection)

Advantages of level sensors

Even if the amount remaining in a container cannot be verified visually, level sensors can continuously measure the remaining level. This can prevent problems such as material leakage or dry boiling in a heating tank.

Using a level sensor prevents problems such as those caused by empty material tanks. If a level switch is installed and the lower limit is set, the material can be refilled in a reasonable time. The use of a level indicator allows continuous checking of the remaining level. Level-wide alarms or outputs can be configured to ensure proper reset. Also, some problems can be detected early and larger problems can be prevented. For example, if the residual fill level does not change continuously despite continuous system operation, this may indicate a blockage.

Choosing level sensors with no moving parts reduces the risk of malfunction. Stable operation can be achieved, for example, by selecting ultrasonic level switches that can detect and measure non-contact targets. Certain "probe-type" level sensors can be affected by muddy water, viscous liquids, or dirt.

Liquid level sensors that use moving parts, such as traditional float types that monitor a float or positive displacement types, have a high risk of damage or malfunction and require frequent maintenance. Due to their design, they are not suitable for viscous liquids. Ultrasonic level switches can sense liquid levels without contact, and command pulse level indicators offer excellent detection performance and are less affected by viscous liquids and debris. Because these instruments have no moving parts, they reduce the risk of malfunction, offer greater stability, and require less maintenance.

It is impossible to constantly monitor the readings of the level sensors in the tank. In addition to the level, other elements such as pressure, temperature and flow are often also managed. IO-Link compatible level sensors enable intelligent operation through a simple network connection with simplified wiring.

The use of IO-Link masters is increasing, since they can connect several different IO-Link sensors one by one with a single M12 connector. This eliminates time-consuming traditional cabling, the number of cables is drastically reduced, and the sources of trouble are reduced. For example, the KEYENCE FLSeries pulse level sensor can be connected to an IO-Link master with a single cable. Since several types of sensors can be connected at the same time, not only the tank level, but also the pressure and temperature in the tank and the flow rate in the pipeline can be easily managed.

Level Sensor Case Studies

Management of the level of liquids in production plants: management of residual and consumption amounts of chemical products used for cleaning (detergents)

Various chemicals are used in cleaning processes. Liquid level sensors are used for the management of these chemical products (detergents) used in the cleaning process. Liquid level monitoring allows for accurate management of remaining and used chemical levels. However, conventional level sensors are mostly made of metal and are not suitable for level management of these chemicals. The KEYENCE FL series pulse level sensor is available in plastic type and can be used for all chemicals including hydrochloric acid, nitric acid, and hydrogen fluoride. In addition to chemicals, this model is impervious to corrosive solutions and viscous liquids, so it can be used reliably for any type of chemical.

Liquid level management in production plants: Management of the remaining and used amounts of refrigerant

In production plants a wide variety of liquids and solutions must be handled. This includes level control (residual level management) of liquids in tanks such as coolants, oils, greases and other lubricants. Using a liquid level sensor is an effective way to maintain the correct amount of refrigerant or operating oil to keep equipment running efficiently. These sensors can also anticipate problems and save energy. However, conventional level sensors have big problems with false readings caused by dirt, foam, and condensation. KEYENCE FLSeries Pulse Level Sensor can stably measure liquid level at all times without detection errors caused by liquid conditions. It can be used for both water and oil with accurate detection even if the liquid contains solid particles. The viscosity of the liquid also does not affect detection.

Level detection of various workpieces and materials such as metal and glass

Ultrasonic level sensors (level switches) enable the detection not only of liquid surfaces, but also of various work pieces, e.g. B. made of metal or glass, which are difficult to detect with retroreflective photoelectric sensors. The KEYENCE FW series high-performance digital ultrasonic sensor can perform detection without being affected by color or background changes. Processes such as handling black tires, printed circuit boards, black rubber sheets and other work pieces with low reflectivity are not a problem. It also allows for online detection of targets without being compromised by transparency, color changes, or bright backgrounds. These include wafer glass with water droplets, curved car glass panels, clear containers with curved surfaces, and cans with small patterns and lettering on their surfaces. In resin molding machines, the remaining amount of molding material (pellets) in the hopper can be detected. The fill level can also be detected when the color of the granules changes.

More details

Frequently asked questions about level sensors

Some types of level sensors can be affected by shape or obstacles. The KEYENCE FLSeries Heart Rate Sensor is not affected by surrounding obstacles. Using the automatic environment update algorithm, the sensor can capture reflected waves, detect obstacles, and account for unique internal shapes. This eliminates a bug detection caused by the installation environment. The data of the reflected waves from the environment is updated in real time, so only the surface of the liquid is detected. As a result, the sensor can be installed in the tank without concern for the internal shape or mixing paddles.

The KEYENCE FL series pulse level sensor can detect any type of liquid, so there is no need to change the setting when the liquid changes. The sensor is equipped with an automatic permittivity adjustment algorithm that automatically determines the type of liquid to be measured. Automatically adjusts the detection sensitivity according to the liquid. This allows the sensor to detect various liquids including water, oils and chemicals with a single probe without adjustment.

With a capacitive level sensor, highly viscous liquids such as egg whites, mayonnaise, or jelly that stick to the probe can affect the reading. It takes time and effort to remove these viscous liquids from the sensor. The KEYENCE FLSeries Pulse Level Sensor can continue stable detection even after the probe is dirty by using the probe detection algorithm that automatically optimizes liquid level detection. In short, the FL can differentiate between the liquid level and the debris in the probe. If the accumulation or environmental changes are too large to allow stable detection, a warning signal can be given before problems arise. This can minimize the frequency of sensor cleaning.

There are different types of level sensors designed for different applications and characteristics. This section presents typical types of level sensors suitable for each application. Important considerations when choosing a level sensor, such as: B. Target contact and the use of moving parts are also described.

Main applications and suitable level sensors

Detection of water, oil and chemical level

Float type (contact type, moving parts used):
This type is inexpensive and can be used for different types of liquids. However, they may not be usable for some high viscosity liquids, low specific gravity liquids, or high temperature or high pressure places.

Lead Pulse Type (contact type, no moving parts used):
High performance and low maintenance. Since the detection is based on a reflection phenomenon, it is not affected by the type or condition of the liquids. This is a contact type, so care must be taken in places where a high level of cleanliness is required.

detection of level of water, oil and chemical products; Liquid level control at various points

Displacer type (contact type, moving parts used):
Low cost and high environmental resistance. The length of the sensor can be changed with a cable and the position of the float can be adjusted as desired. Performance may be affected by buildup or floating. A readjustment is required when the specific gravity of the fluid changes.

Liquids, slurries, powders and other targets in any form

Ultrasonic type (non-contact type, no moving parts are used):
Non-contact detection is less affected by debris and handling is easy. However, these sensors cannot be used in a vacuum. Detection may not be possible in high temperature or high pressure environments, or in environments with dust or obstacles.

Capacitance type (contact type, no moving parts used):
These sensors are high performance and can detect and measure even in harsh environments, such as high temperatures or pressures. A measurement is not possible if the permittivity of the liquid changes. An empty tank configuration is required.

mud level

Pressure type (contact type, no moving parts used):
These sensors are inexpensive and can be used for different liquids. The structure and installation are simple, and the precision is high. Under high temperature or high pressure, the errors may increase. Measurements are temporarily not possible. The continuous reading version can only be installed at the bottom of the tank.

Level detection of conductive liquids

Electrode type (contact type, no moving parts used):
Cheap. An electrode pole of the required length can be connected. These sensors can be used outdoors. The insulators cannot be detected. Detection is easily affected by debris. Multipoint adjustment is difficult and continuous measurement is impossible.

Important points when choosing liquid level sensors

For models that come into contact with targets, it is necessary to choose one that is resistant to false detection of dirt. In many cases, models with moving parts require more frequent maintenance and carry a greater risk of malfunction during operation. This section presents a contact model and a non-contact model of liquid level sensors, which can be used for various purposes and various installation conditions.

Contact type, no moving parts used

The traditional disadvantage of this method was false detection due to dirt on the probe (the part that comes into contact with the liquid). We solved this problem by using sensor technology and algorithms to offer flexible installation, stability, and low maintenance. The sensor is also IO-Link compatible making it suitable for the latest factory automation environments.

Detection Guide FL Series Pulse Level Sensor

Non-contact type, no moving parts are used

Level sensors that use ultrasonic waves fall into this category. They measure the level of the liquid based on the time it takes for the ultrasonic waves to strike and return from the surface of the liquid. Because the sensors do not touch the target, they offer easy maintenance and operation regardless of target characteristics. The traditional drawback has been poor environmental durability. Our sensors offer high resistance so they can be used in a variety of conditions.

FW Series High Performance Digital Ultrasonic Sensors

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