What is Capacitive Sensor And How Does It Work and Types?

What is Capacitive Sensor And How Does It Work and Types?

Capacitive sensors have been in use for quite some time now. They are a proximity sensor that detects the nearby objects through their electric field effect. Read on this blog further to understand everything about capacitive sensors. This comprehensive guide is a detailed look into what is a capacitive sensor, its working and types.

What is a Capacitive Sensor?

A capacitive sensor is an electronic device that detects targets like solids or liquids without physical contact. These devices produce an electrical field to detect the targets from the sensor’s detecting end. This sensor detects any target that interrupts its electrical field through its sensor. A capacitive sensor can detect solid materials like paper, wood, glass, plastic, and cloth. It can also detect liquid materials like water, paint, and oil. 

Advantages of Capacitive Sensor

Below are the most significant advantages of capacitive sensor

  • These sensors can detect targets using varying containers. 
  • They detect non-metallic targets. 
  • The capacitive sensor’s construction is simple. 
  • They are affordable. 
  • These sensors have a good frequency resolution and response. 
  • They adjust to different types of materials. 
  • These sensors have high sensitivity.
  • They can be operated through a small energy magnitude. 
  • These sensors detect liquid and solid targets. 
  • Capacitive sensors measure pressure, force, humidity, etc. 

Working Principle of Capacitive Sensor

A capacitive sensor works similarly to a normal capacitor. These sensors have a metal plate within the sensing face, which is connected electrically to an oscillator circuit. The target detected by the sensor acts as the next plate of the capacitor. Unlike an inductive sensor that generates an electromagnetic field, a capacitive sensor generates an electrostatic field. 

The capacitive sensor has a high-frequency oscillator. It also has a sensing surface that is formed with two metal electrodes. As soon as an object comes close to the sensing surface of the sensor, it moves into the electrostatic field of the sensor’s electrodes. This changes the oscillator's capacitance. As a result, the oscillator circuit oscillates and changes the output condition of the sensor once it arrives at a specific amplitude. The amplitude of the oscillator reduces as soon as the target goes away from the capacitive sensor. This switches the capacitive sensor back to its original position. The typical detecting range of a capacitive sensor is around 25 mm or 1 inch. However, in some sensors, this range can be extended up to 2 inches. 

Capacitive sensors detect the superior dielectric constant of an object. They make detecting material within non-metallic containers possible because a liquid’s dielectric constant is higher than the container’s. Hence, this enables the sensor to detect a liquid inside a container. 

Types of Capacitive Sensors

Capacitive sensors provide non-contact target detection. They effortlessly detect the existence and non-existence of a target. However, they also detect liquid level, pressure, flow and spacing. Capacitive sensors used in different industries are made of varying materials. Below are the various types of capacitive sensors


One of the first types of capacitive sensors is the miniature sensor. These sensors have a cylindrical or wafer shape, making it possible to place them even in the most compact places. Miniature sensors are primarily used to control and monitor machine processes. Miniature sensor heads use an external amplifier to fit perfectly within tight spaces. 


The next type is the cylindrical sensor. These sensors are larger than miniature capacitive sensors. They mainly consist of flush and non-flush mounting options, adjustable sensing distance and a range of housing diameters. Cylindrical capacitive sensors provide contact-free proximity or level detection directly or through a container wall. 

High Temperature

Next on the list are high-temperature capacitive sensors. These are used where the sensor head is prone to coming in contact with extreme temperatures. High-temperature sensors work even when they are in direct contact with hot materials and temperatures. They perfectly detect liquids and solids' temperature levels even in the most severe conditions. 


Another type of capacitive sensor is the analogue capacitive sensor. These sensors work like typical capacitive sensors. However, they have different advantages based on their use. These sensors are used for material selection and to monitor thickness and concentration. 


In the End

The role of capacitive sensors is indispensable. They protect circuits from various elements like water, oil, paper, wood and cloth. Reading this post must have introduced you to what is a capacitive sensor. If you want these sensors for your industry, ensure you buy the right quality. But where can you find any of the different types of capacitive sensors? You guessed it right- Schneider eShop is your destination for buying the best capacitive sensors. 

Frequently Asked Questions

Q1. What Factors Affect the Performance of a Capacitive Sensor?

Ans: Some of the many factors that affect the performance of a capacitive sensor are as follows. 

  • dielectric properties of the target material
  • distance between the sensor and the object
  • environmental conditions such as temperature and humidity
  • presence of nearby conductive or dielectric materials
  • sensor's design and calibration
  • stability of the sensor's power supply

Q2. How to Maintain a Capacitive Sensor?

Ans: Capacitive sensors need minimal maintenance. They require regular inspection of its connections. You must look for any signs of wear or damage. Also, they must be cleaned regularly to remove dust, dirt and residue. 

Q3. What are the Applications of a Capacitive Sensor?

Ans: A capacitive sensor has the following applications.

  • They detect and measure conductive things or have dielectric.
  • These sensors frequently find the change within a conductive target position. 
  • These types of sensors are effective in measuring density, non-conductor location, presence and thickness. 
  • Capacitive sensors detect or measure position, acceleration, proximity, displacement, humidity and fluid level.
  • Capacitive sensing touch screens are input devices for mobile phones, digital audio players, and tablets.