A basic capacitive liquid level sensor is designed to measure the level of a liquid inside a container or tank using the principle of capacitance. Capacitance is the ability of a system to store an electric charge. In this type of sensor, the capacitance between two conductive plates is used to detect the liquid level.
The working principle of a basic capacitive liquid level sensor can be explained as follows:
Construction: The sensor typically consists of two conductive plates arranged in parallel, and they act as the capacitor's electrodes. These plates can be made of metal or a conductive material. One plate is positioned at the bottom of the container (the sensing plate), and the other is placed above the liquid surface at a fixed distance (the reference plate).
Capacitance variation: When there is air or gas between the two plates (i.e., the liquid level is below the sensing plate), the capacitance between the plates is relatively low. This is because air has a lower dielectric constant than the liquid, and the capacitance is directly proportional to the dielectric constant of the material between the plates.
Liquid presence: As the liquid level rises and reaches the sensing plate, it changes the dielectric constant between the plates. Liquids have higher dielectric constants compared to air, so the capacitance between the plates increases when the liquid is present.
Capacitance measurement: The sensor is connected to an electronic circuit, which measures the capacitance between the two plates. The circuit can be designed to detect changes in capacitance and convert them into a proportional electrical signal.
Calibration: Before using the sensor, it is usually calibrated to establish the relationship between the liquid level and the capacitance. This calibration process involves determining the capacitance values corresponding to different liquid levels.
Output: The sensor's output can be displayed on a digital or analog interface, providing information about the liquid level. The output can be in the form of a continuous level reading or discrete level indications.
Applications:
Capacitive liquid level sensors are commonly used in various industries, including chemical processing, water treatment, oil and gas, food and beverage, and automotive.
They are suitable for measuring non-conductive liquids such as water, oil, fuel, and various chemicals.
However, they may not be suitable for highly conductive liquids or corrosive substances, as they can affect the sensor's accuracy and durability.
Overall, the basic capacitive liquid level sensor offers a simple and effective way to monitor liquid levels in a container without direct contact with the liquid, making it a popular choice in many industrial and commercial applications.