Level Measurement Instruments

This website is used as a source of information on level instruments including level sensors, level switches, level indicators and level controllers. The various techniques that are used for level monitoring and control in process plants and what are the measures to take for installing a sensor. Let us start by looking into the main level sensing techniques -

What is a level sensor? - A level sensor is a process control instrument that is used to measure the level of liquids in natural or industrial environment. These level sensors thus, can be of two types - one that measure the level of flowing rivers, canals or other water bodies and the others which measure the water in hoppers, vessels and tanks. One such liquid level switch is Elixir from Sapcon.

A level sensor may monitor the level of fluid continuously or at specific points. The former is known as a continuous level sensor while the latter as point level sensor. The point level sensors can be further broken don into single point level sensors and multi-point level sensors.

There are many factors that play a role in deciding the optimal solution for an industrial process plant. along with the plant condition and the state of the service material, the dielectric constant of the service material, temperature, pressure, hopper size and shape, vibration and price are some issues to have a look at.

Vibrating Level Sensor

These sensors are appropriate for point level measurement of very fine, fine, granular and highly fluidized service material. These sensors minimize the service material build up and are ideal for highly static bulk powder environments. Vibrating fork Level Sensor

Rotating Paddle Level Sensors

The oldest of the lot. a paddle wheel is rotated by a low speed motor. When the paddle is stalled by material, the motor is rotated on its shaft by its own torque until a flange mounted on the motor contacts a mechanical switch. Material to build up the paddle assumes an importance here as this material should not be tacky.

Conductivity based level sensors

Water and other fluids are best level measured using these types of level sensors. Also suitable of highly corrosive liquids such as caustic soda, ferric chloride, and similar liquids, these sensors should have a teflon covering. Learn more about how a typical water level sensor works.

Capacitance Level Sensors

A wide variety of service material including solids, slurries as well as liquids might be measured with a capacitance based level limit switch/sensor. The technique is also know as the RF/microprocessor technique. The dielectric constant of the material is never a problem with capacitance based level sensing solution. You can use it for any service material.

admittance based Level Sensors

Ultrasonic Level Sensors

These sensors are non contact type level sensors where the service material and the probes never come in contact of each other. Oil, grease, latex and other highly viscous liquids require this level sensing technology. Open channel flow management can also be effectively done using an ultrasonic level measurement solution, though it isn't always required. a capacitance based solution can work well for Open channel flow management sensor.

Moisture and temperature affect the use of ultrasonic technology since the sound waves get affected by them. It is thus best to use a temperature/humidity sensor along with an ultrasonic level sensor to provide interference free signal output.