Liquid level sensors have been a cornerstone in many industries for decades, offering a reliable and cost-effective solution for detecting leaks and measuring levels in various applications from industrial, medical, and domestic to printing, agriculture, automotive, and white goods. With so many level-sensing alternatives, customers may need to know the range of advanced technologies available. As such, it’s no wonder that customers often ask us why they should choose one technology over another. Even manufacturers may be surprised at the variety and intelligence of level-sensing solutions.
Processes that used to require expensive and complex equipment can now be achieved with cost-effective, reliable, robust, highly accurate, and easy to install creative, innovative, and intelligent technologies. In addition, historically challenging fluids like soapy bubbles, milk, and sticky substances like glue and ink are much easier to detect with various level sensing technologies.
The need for level-sensing devices is evident in today’s competitive industry, where companies constantly strive to improve quality, reduce costs, and minimize inefficiencies and waste. Without such technology, companies would be taking a risk by offering solutions that may not perform optimally. Therefore, level-sensing devices are essential for companies to maximize their efficiency and profitability.
- Optical
- Vibrating or Tuning Fork
- Ultrasonic
- Float
- Capacitance
- Radar
- Conductivity or resistance
- Optical Level Switches
Pros:
They are compact and have no moving parts, making them perfect for tight spaces. They have high pressure and temperature capabilities, enabling them to detect even tiny amounts of liquid.
Cons:
These switches are invasive, as the sensor requires physical contact with the liquid, requiring power and consuming space. Additionally, thick substances can cause the coating on the prism to wear away, leading to inaccurate readings.
Application:
Suitable for measuring tank levels and detecting leaks
Optical Level Switches are a type of level-sensing technology used to detect the presence of a liquid. They comprise an LED and a phototransistor housed within the sensor tip. The infrared light is reflected back to the detector when the tip is placed in the air. When the tip is placed in liquid, the infrared light is refracted away from the sensor. These solid-state switches are reliable and ideal for point-level sensing applications. With their small size and high level of accuracy, optical level switches are the go-to device for precise level sensing. Optical liquid-level switches provide accurate, reliable, and cost-effective high, low, and intermediate-level detection for practically any size tank — from small to large tanks — with no delay in readings. They are also perfect for detecting leaks and preventing costly damage. Even in tanks with high levels of reflective light, such as small reflective tanks, mirrored tanks, bubbles, milk, or coating fluids, these switches can still provide accurate readings.
- Capacitance
Pros:
Capacitance is a reliable, non-invasive, compact, and accurate solid-state sensing technology. It requires minimal calibration and can be used in various liquids, making it suitable for multiple applications.
Cons:
In some cases, capacitance may require additional calibration to ensure accuracy. Additionally, it cannot be used in all liquids.
Applications:
Capacitance is ideal for tank level monitoring in the chemical, food, water treatment, power, and brewery industries. Its accuracy and reliability make it a valuable tool for monitoring and controlling tank levels.
Capacitance level sensors are an effective tool for measuring the level of process fluids in tanks and containers. These sensors detect changes in capacitance between two electrodes when exposed to fluids with different dielectric constants than air. A high-dielectric-constant version is available as well as one for fluids with low dielectric constants. Capacitance level sensors can be used with various solids, liquids, and mixed materials and are available in contact and non-contact configurations. When selecting a device, it is vital to ensure that the capacitance sensor is compatible with the specific material and tank design. Furthermore, the sensor should be calibrated to the material to account for the varying dielectric constants. Finally, as capacitance level sensors are contact-based, the reliability of these sensors may be impacted by fluids sticking to the probe.
- Ultrasonic
Pros:
Ultrasonic sensors provide reliable and compact solutions to non-contact applications with highly dense and bulk solids. They have no moving parts, are unaffected by media properties, and can be remotely monitored.
Cons:
Ultrasonic sensors can be expensive and invasive, and their performance can be affected by environmental elements.
Applications:
Ultrasonic sensors are ideal for non-contact applications with highly dense and bulk solids and systems that require remote monitoring. They are also helpful in measuring liquid levels and detecting objects in challenging locations.
Ultrasonic sensors measure levels by sending out sound waves which bounce off liquid surfaces and back to the sensor. The time for the sound waves to travel from the sensor to the liquid and back is relative to the distance between them. However, the time the sensor takes to react may vary based on various factors in the atmosphere above the media, such as turbulence, foam, and temperature. Therefore, the mounting position of the sensor must be carefully considered to obtain accurate results.
- Microwave/Radar
Pros:
Very accurate, no calibration required, and multiple output options make microwaves/radars ideal for many applications. – Can detect moisture, vapor, and dust in varying temperatures.
Cons:
Expensive compared to other technologies – Can be affected by the environment, leading to limited detection range.
Applications:
Ideal for use in moist, vaporous, and dusty environments where temperatures can vary – Used in many systems that require accurate measurement of temperature, humidity, and other environmental factors
Radar is similar to ultrasonic in principle, however, pulses travel faster, offering more reliable and repeatable measurements. The dielectric constant of the fluid can affect the accuracy of these measurements, but radar can still provide exact level information and compensate for fixed structures within the container. The initial cost of radar sensors may be relatively high, but now more manufacturers are making radar technology more accessible to the broader market. These sensors are also among the few that work well in foam and sticky substances.
- Vibrating or Tuning Fork
Pros:
Compact and cost-effective, non-invasive.
Cons:
Limited uses.
Applications:
Vibrating or Tuning Forks are ideal for level control of liquids, powders, and fine-grained solids within the mining, chemical processing, and food and beverage industries. Their compact size and affordability make them an excellent choice for these industries.
The vibrating sensor technology is perfect for various level control applications, from solid and liquid materials to sticky materials and foam, to powders and fine-grained solids. Tuning forks are limited to overfill or run dry-type applications but can be used with continuous-level detection systems for alarm points for overfilling and leaks. With this versatile sensor technology and alarm capabilities, vibrating sensors provide a comprehensive solution for efficient and reliable level control.
- Conductivity or Resistance
Pros:
This technology is ideal for measuring tank levels, monitoring reagents, and measuring the levels of highly corrosive liquids. It has no moving parts and is easy to use, making it an economical choice.
Cons:
This technology is invasive, meaning liquids must be conducive to working correctly. Additionally, the probe can be prone to erosion over time.
Applications:
This technology is perfect for tank level measurement for boiler water, reagent monitoring, and measuring the levels of highly corrosive liquids.
Conductive sensors are ideal for point-level sensing of highly corrosive and conductive fluids. They feature two differently-sized metallic probes – one long and one short – inserted into a tank. The lengthy investigation transmits a low voltage while the shorter probe is cut so that its tip is at the switching point. The current flows across both probes to activate the switch when the probes are liquid. These devices are safe due to their low voltages and currents and are also easy to use and install. However, regular maintenance must be conducted to ensure there is no build-up on the probe, or it will not work correctly.
- Float Switch
Pros:
The Float Switch is an effective and inexpensive solution for tank-level applications, such as monitoring water, oil, hydraulic fluids, and chemicals. It is a non-powered, direct indication device with various outputs. It can provide a clear indication when a large amount of liquid is present.
Cons:
It is an invasive device with moving parts and is quite large. It also requires a large amount of liquid before the float makes contact.
Application:
It is an excellent choice for tank-level applications, providing a clear indication at a relatively low cost.
Float switches are a reliable and cost-effective technology for sensing water levels. This simple yet effective design offers long-term reliability at an attractive price, featuring a magnetic float and a magnetic reed switch housed in secure housing. For optimal installation, suppliers provide a range of mounting options, such as flat/side mounting and vertical mounting. Depending on the chosen mounting style, there are different design and construction requirements for the tank or container where the switch will be situated.