Various level sensors are used for industrial purposes, here's a brief on level sensors, their types as well as their various applications.
Different Industrial Applications:
Different types of Level sensors are used in every process and manufacturing of Pharma, Automotive, Dairy, Chemical, Paint, Water Treatment, Food and Beverages industries, etc. Furthermore, apart from industrial use, they are also used in many household appliances such as ice makers in refrigerators.
Some of the common applications of level sensors for direct contact with media are:
Tank level measurement (for different media such as chemicals, corrosive liquids, powder, hydraulic water, oil, etc.)
Leak detection and level measurement
Media level control
Other types of level sensors come with a non-contact application for continuous level detection where:
Systems need remote monitoring
Systems with varying temperatures
Change in media inside tanks
In the following sections, we will walk you through the different types of level sensors appropriate for the above-mentioned applications.
Types of Level Sensors for Various Applications:
There are different types of level sensors designed specifically for continuous level measurement and point level detection respectively; that provide optimum solutions using a unique technology selection. They are economical standard sensors that are very easy to integrate with matching process connections.
Level sensors can be divided into two categories:
Point Level Measurement (indicates when the media has reached a particular point in the container).
Continuous Level Measurement (shows the continuous level of the media as it falls and rises).
Point Level Sensors:
Unlike the vibrating fork, Baumer’s Cleverlevel switch gives precise measurements as it works on the frequency sweep technology that radiates signal from its sensor tip to the media. The media acts as a virtual capacitor between the sensor tip and metal housing; also the virtual capacitance depends on the DK value of the media.
Following are the different types of point level sensors for various applications:
Optical level sensors
Application: Tank level measurement and leak detection.
Level detection with optical sensors enables the level and leakage control using the principle of photoelectric level measurement; by converting light rays into electric signals that measure the physical quantity of light and then translates it to measurement. These sensors are robust and chemically resistant sensors for direct contact as they do not have any moving parts and are not affected by high temperature or pressure. They also, facilitate contactless level detection in ascending pipes. Furthermore, these sensors are compact and can be used in liquid applications as they suppress foam and air bubbles up to 3mm. These optical level sensors can be used as low-level indicators to avoid dry conditions while using coolant, hydraulics, or even oil.
Capacitance Level Sensors
Application: Tank level measurement in water treatment, chemical, power, food, brewery industries, and battery industries and involving high pressure and temperature.
The capacitive level is used to determine liquid levels in tanks by utilizing the aid of an electric field, as it is a proximity sensor that produces an electrical charge and detects a level by the effect of this electrical current. This method can be performed both non-contact from the outside and with media contacts. The capacitance level sensors are small and precise devices that do not have any moving parts and are even affordable than others. However, the capacitance level measurement cannot be calibrated and can only detect some liquids.
Vibrating (Tuning Fork) Level Sensors
Application: level control of media (liquid, powder, and finely grained solids) within F&B, chemical processing, and mining industries.
Tuning fork sensors use a fork-shaped sensing device that vibrates at a natural frequency; it uses differences in pressure and vibration to measure liquid levels. As the level changes, the frequency of the fork also changes. The vibrating tuning fork level sensor is invasive to the product and is compact, simple to install, and essentially maintenance-free.
However, it is important to note that over a period of time they are bound to give faulty measurements. The major reasons for faulty readings are a build-up of foam, high viscosity, electrostatic and adhesive substances that get lodged in the forks.
Application: Tank level applications where media like chemicals, water, oil, and hydraulic fluids are used.
The float switch is a non-powered device that gives a direct indication of measurement by opening or closing the circuit as and when the media level rises or falls on which it floats. The drawback of the float switch is that it has moving parts and is large-sized, unlike other level sensors.
Conductivity (or Resistance) Level Sensors
Applications: Tank level measurement for highly corrosive liquids, reagent monitoring, and boiler water.
The conductivity sensor (also known as a resistance sensor) uses a probe (an instrument) having a pair of electrodes to read conductivity.
The electrodes create a part on the circuit when the media covers the probe, and this causes the current to flow, giving alerts/ indications on a high and low level. This point-level sensor is simple to use, it does not include any moving parts.
Continuous Level Sensors:
Below mentioned are the different types of continuous level sensors for various applications:
Ultrasonic Level Sensors
Application: for contactless applications, high contamination tolerance and used in systems that require remote monitoring.
The ultrasonic level sensor measures the transmission time of the ultrasonic signal reflected by the medium to be measured as this sensor emits and receives ultrasonic waves. It is a contactless sensor that is material independent, does not include any moving parts, and has high contamination tolerance suitable even for very small containers. As this type of sensor is a contactless sensor, it is insensitive to dust, light, or water and also remains protected against aggressive media. Ultrasonic Level sensors are also non-invasive and unchanged by the material’s properties.
Application: Used in systems with varying temperatures; and in moist, dusty, and vaporous environments. Also, works well in foam and sticky substances.
Radar sensors are devices or instruments that transform microwave echo signals into electrical signals and transmit microwaves through an antenna on the sensor. They use wireless sensing technology and can provide very precise level information, that is the time taken to reflect back the microwaves from the product to the sensor is proportional to the level of the product. These types of sensors can be used for applications like varying temperature, pressure, moist environments, as microwaves can easily go through these media without involving air molecules for energy transmission. These sensors can measure varied media like pastes, liquids, solids, and powders. Radar sensors are non-invasive and very precise.
Hydrostatic Pressure Transmitter
A pressure transmitter is installed at bottom of the tank. Hydrostatic Pressure Transmitter detects extremely accurate levels, as the level measurement is based on pressure measurement. Any change or fluctuation in the hydrostatic pressure reflects in the filling level and is accurately detected by the sensor giving a corresponding pressure output.
Even though there isn’t any universal technique for the selection of level measuring devices that is suitable for a particular application; a detailed study of various parameters can help to select the right level sensor for every application.