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Industries use several different types of level sensors to detect their products. In this video, we are going to talk about the different types of level sensors used in the industry.
Level Sensors can be broken into two classifications, point level measurement, and continuous level measuring.
Point level measurement indicates when a product is present at a certain point and continuous level measuring indicates the continuous level of a product as it rises and falls.
The sensors for point level indication are “Capacitance”, “Optical”, “Conductivity”, “Vibrating” (Tuning Fork) and “Float Switch”.
The sensors for continuous level measuring are “Ultrasonic” and “Radar” (or Microwave).
A capacitance sensor is a proximity sensor that gives off an electrical field and detects a level by the effect on its electrical field.
These sensors are small, less expensive than other sensors, invasive to the product, accurate, and have no moving parts. However, they do have to be calibrated and will only detect certain liquids.
Capacitance sensors can be used in liquid storage tanks. A water treatment facility that has storage tanks would be an ideal use for a capacitance sensor.
The next point level sensor we will talk about is an optical level sensor. Optical sensors work by converting light rays into electrical signals which measure a physical quantity of light then translate it into a measurement.
These sensors have no moving parts, they are not affected by high pressure or temperature, are small in size, and can be used in liquid applications.
Another style of point level sensor is conductivity or resistance. A conductivity or resistance sensor uses a probe to read conductivity. The probe has a pair of electrodes and applies alternating current to them.
When a liquid covers the probe its electrodes form a part on an electric circuit, causing current to flow which signals a high or low level.
The advantages of using a conductivity level sensor are there are no moving parts, they are low cost, and fairly easy to use.
The disadvantages are they are invasive, meaning they must touch the product being sensed, they only sense conductive liquids, and the probe will erode over time.
Vibrating or tuning forks is another type of point level sensor. They use a fork-shaped sensing element with two tines. The fork vibrates at its natural resonant frequency. As the level changes, the frequency of the fork will change detecting the level.
These sensors are cost effective and are also compact. They are invasive to the product, meaning they have to touch the material to sense the level. These sensors are easy to install and are essentially maintenance-free.
Float switches use a float, a device that will raise or lower when a product is applied or removed, which will open or close a circuit as the level raises or lowers moving the float.
The advantages of a float switch are that it is a nonpowered device, it provides a direct indication, and they are inexpensive.
The disadvantages are they are invasive to the product, they have moving parts, and can be large in size. Float switches will only give an indication for a high or low level they cannot measure a variable level.
ultrasonic sensors work by emitting and receiving ultrasonic waves. The time it takes for the waves to reflect back is how distance is measured.
These sensors have no moving parts, are compact, and reliable.
The disadvantage of using this type of sensor is that they can be expensive and in some situations, the environment can have a negative effect on them.
The benefits of ultrasonic sensors are that they are non-invasive, or non-contact, they are unaffected by the properties of the material they are sensing, and they are self-cleaning because of the vibrations they give off.
Radar or microwave is also a continuous level sensor.
These sensors transmit microwaves by an antenna on the radar sensor.
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