Liquid Level Sensor
By Megha Parolkar on September 20, 2019
Introduction: Liquid Level Sensor
The fastest-growing industries change its requirement at every passing hour and demands level instruments that maintain standard quality with lower cost. Sapcon is a trustworthy partner to fulfill the demands of level measuring devices and considered as one of the efficient choices.
Detection of liquid levels in industries is quite challenging as compared to solid media due to its properties and behavior. The stringent performance of liquids engages costly equipment to manage the process of level measurement. To make this operation economical, liquid level sensors are introduced. The liquid level sensor is the type of level instrument used in the process automation industry to detect the presence of liquids kept in process vessels, tanks, silos, hoppers, etc. The process followed by this level measurement is known as liquid level measurement.
How does a Liquid Level Sensor works?
The working principle of the liquid level sensor depends on the type of technology selected. Sapcon has an array of liquid level sensors that are based on Vibrating Fork, Capacitance, RF Admittance, and Conductivity principle. The following are the principle which can be useful in liquid type of application media:
- Vibrating Fork: The vibration type level switch works on the tuning fork principle which vibrates at its natural frequency in the absence of material. The vibrating fork level sensors are available with hygienic mountings that support to mount the level sensor in a hygienic environment. The compact size and fast switching of these devices make it fruitful for packaging machines.
- Capacitance: The capacitive level switch works on the capacitance principle which detects the changing value of capacitance. The properties of liquid material are precisely taken into account while designing the capacitance based level sensor. The Twin Probe and Still Well arrangement plays crucial role in these capacitive liquid level switches for material having lower dielectric media.
- RF-Admittance: The admittance based level switch works on the capacitance measurement principle with heavy build-up. These admittance based level sensors provide exceptional services even in sticky media. The designing part of the admittance level sensor is introduced with "Shield" which identifies the difference between coating and the real material.
- Conductivity: The conductivity based level sensor is also known as water level sensor which is specially designed to sense the water level. These water level sensor is generally mounted in water tanks where water are stored in large quantity.
Liquid Level Sensor Types
The liquid level sensors are broadly categorized into two parts:
- Liquid Level Switch - It is also known as Point Level Switch which determines the level only at specific points. These types of level sensors are used to detect the level at high or low points. These types of level measuring devices can be helpful to prevent overflow and dry run conditions.
- Liquid Level Transmitter - It is also known as a Continuous Level Transmitter which continuously measures the liquid. This type of level sensors monitors the level at every certain period and gives real-time results.
Product Selection: Based on Application Media
Different types of level instruments are available for level detection but before selecting the sensors, the exact type of application media should be known for betterment of output and process.
- Sticky Media
- Conductive Media
- Corrosive Media
- Foaming Media
Material that can adhere to the surface of the instrument or create a coating on the probe of the level sensor is known as sticky material. Viscosity is the main parameter used to identify whether the material is sticky or not.
It give resistance to flow an electric current and it causes short circuits when it comes in contact with the metal directly.
A highly reactive material which damages the external body directly or through chemical reaction is known as corrosive material. Acids and Bases are the most common types of corrosive material.
Liquids that build foam on the surface of the material are known as foaming material and require detection for precise level measurement.
Product Selection: Based on Parameters
The liquid materials are processed at a high temperature which requires standoff arrangement and insulation protection to isolate sense and ground to protect the level instruments.
- PTFE Insulation
- Ceramic Insulation
Hygiene is the critical requirement of Dairy and pharmaceutical industries as it deals with perishable material that are sensitive to contamination. To meet the hygienic standard following points should be taken into account while designing the level instruments.
- Surface Finish
- Geometry Considerations
- Mounting Arrangement
For more details on hygienic requirements, refer EHEDG Certification for Fork Level Sensor article.