Do you know these characteristics of the level sensor?

- Dec 05, 2019-

Difference between level sensor and level meter:
In simple terms, the liquid level switch outputs a switching signal based on the level of the liquid. The liquid level sensor converts the height of the liquid level into an electrical signal and outputs it. The actual height of the liquid level can be output by processing the signal through a PLC or data collector.
What does it mean, the liquid level gauge only provides the switching signal. When the liquid level is reached, the switching signal is output. This signal is used to close the valve or the pump. The liquid level sensor can display the liquid level data in real time, which is more widely used. Maybe someone will ask if there is any output for this? Of course there is! All real-time data has been collected. This data is much more usable. Through the data of the liquid level, a comparison instruction can be written in the PLC. When a certain set value is reached, the out output is sufficient.

Advantages and disadvantages of different types of level sensors:
1. Float type liquid level sensor
The buoy floating on the water surface is used for detection, and the buoy varies with the level of the liquid. In practical applications, the attachments on the buoy, the damage to the buoy, the foam generated on the liquid surface, and the liquid level fluctuations will cause false detection, and the viscous liquid cannot be detected.
The buoy installation method as following:


2. Electrode type liquid level sensor
This sensor uses the principle of energization between electrodes to detect. Due to the limitation of detection methods, measurement errors due to coating and condensation may occur in practical applications. In addition, it cannot be used for non-conductive liquids and viscous liquids.
The electrode installation method is following:


3. Ultrasonic liquid level sensor
This is a non-contact sensor. The detection is carried out using the principle of ultrasonic reflection. Since ultrasonic waves are diffused, measurement errors may be caused by reflections from the blocking members in the container. Especially some containers installed outdoors or in high temperature environment can cause measurement errors due to liquid vapor. In some high-speed stirring vessels, errors can be caused by liquid level waves.
The ultrasonic installation diagram is as follows:


4. Capacitive liquid level sensor
Detection is performed in a manner that changes in capacitance caused by changes in the dielectric surface to be measured. This method will cause errors due to liquid deterioration and liquid temperature changes.
The capacitive level sensor is shown below:


5. A new level sensor
The above four sensors have some functional shortcomings and limited detection ranges. Is there a sensor that can eliminate factors such as probe dirt, liquid vapor, liquid surface waves, and changes in liquid viscosity? The answer is yes, there are many sensors on the market with these functions.
Liquid level detection principle: The method using infrared photoelectric principle. When the sensor detects liquid, only a small amount of light is received by the sensor due to the refraction of the water, giving a low voltage signal.

This is the installation way:

Optical water level sensor theory