Home SCI-TECH CAPACITANCE LEVEL SENSORS: AN OVERVIEW

CAPACITANCE LEVEL SENSORS: AN OVERVIEW

by James Vinse

Capacitance level sensors can sense a wide range of solids, liquids (organic and aqueous), and slurries. They detect the amount of the contents present in silos, tanks, or bunkers in various industries. 

 

Based on the functionality, the capacitance sensors have a capacitive level switch and level transmitters installed in them to detect and relay the necessary information needed to monitor the amount and help maintain control over the materials. 

 

This article focuses on comparing the principles, factors, and utility of level switches and transmitters in level measurement sensors.

 

Capacitance Level Sensor

The capacitance level measurement works on the principle of the amount of change in the capacitance of a capacitor. The capacitance circuit uses radio frequency signals to relay the detected levels. 

 

The capacitance of the capacitor, i.e. the probe in the tank or silo, is dependent on the amount of product present inside. Therefore, the change in the capacitance depends on the level of solid or fluid present. 

 

An empty tank would show a lower capacitance while a filled tank would show higher capacitance. One can measure the capacitance by passing a radio-frequency signal between the wall of the tank and the conductive probe which provides information for the level switches to detect.

 

Types of Capacitance Level Measuring Sensors

There are two different types of level measuring sensors: level switches and level transmitters. One can compare the operation of a capacitive level switch to that of an alarm that switches on and off when the material crosses the predetermined level set; they are perfect where extraordinarily high and low levels of fluid need to be measured. 

 

Level transmitters provide the exact measurement of the material. The switch or the transmitter works to alert and activate the necessary response required from the users. 

 

Limit switches alert the user if there is an overflow or shortage of material during operation whereas a limit transmitter helps the user continuously monitor material level. 

 

The detection and output from the devices could be voltage-dependent (based on a fixed voltage range) or voltage free. 

 

For example, if a level sensor set with a detection output signal varying from 5-30 mA would provide the reading of 30 mA for a full tank, 15 mA for a half tank, or five mA for an empty tank and anything above or below would set off an alarm. 

They can relay variations on a point level like in optical liquid switches, vertical and horizontal float switches and ultrasonic level, or continuous levels in submersible level sensors and capacitive level sensors.

 

Factors Affecting the Output of the Capacitance Level Sensors

Although capacitive level switch and level transmitters perform the same function, they vary in their operation. It is essential to understand the different aspects that affect their output to make the right choice for use.

 

One must consider environmental factors while making the selections of level transmitters and level switches as they consist of various materials that have different thresholds for varying pressures and temperatures. 

 

One must also consider the application of the device while selecting the right device, concerning the range of the readings, type of output necessary- analog, relay or digital; their chemical compatibility, the shape, and size of the tanks, and the duration of its working.

 

Benefits and Applications

Capacitance level sensors are proven to be a robust and safe way of measuring liquid or bulk materials. They come to the aid of industries by keeping track of the fluid and avoid unexpected incidents that could have adverse effects on the machinery, process, people, and the environment. 

 

These devices do not have any moving parts and hence are reliable, easy to clean, relatively inexpensive, have low maintenance, and can withstand high pressures and temperatures. 

 

Therefore, one can use them for measuring the levels of materials in various states and temperatures, including granular solids, liquified metals, and gases of high and low temperatures respectively. 

 

One can use them to measure acids and other corrosive substances and viscous materials like milk, glue, and ink, which are usually difficult to detect and more. Markets such as agriculture, industrial, medical, print, food, and beverage industries use capacitance level sensors for leak detection through level measurements. 

 

Due to their ability to quickly detect variations in materials with extreme properties, they are popular in packing industries, plastic and chemical industries, wood, glass, and other ceramic industries that have non-metallic resources.

 

A fair understanding and knowledge about these level sensing devices, their workings and factors, and consultation with product manufacturers would assist in making the correct selection.  

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