Water Turbidity Sensor

Sensor concept:

Turbidity sensor is a low-cost sensor specially used in home appliances, mainly used for measuring the degree of water pollution in washing machines, dishwashers and other products. By measuring the degree of turbidity of the water to judge the cleanliness of the washed items, so as to determine the best washing time.


The turbidity of water is an important criterion for measuring the quality of water quality. my country is a country that lacks water resources and is also a country with serious water pollution. Every year, a large amount of untreated sewage is discharged into lakes and rivers. The water environment situation and the improvement of people’s quality of life requirements, people’s requirements for water quality are also correspondingly improved. Therefore, under this circumstance, vigorously improving the level of water quality testing and popularizing the intensity of water quality monitoring has become an urgent matter.

Basic information on turbidity sensors:

Turbidity is caused by suspended particles in the water. Suspended particles will diffusely reflect incident light. Usually, the scattered light in the direction of 90 degrees is used as the test signal.

The scattered light and turbidity have a multi-segment linear relationship, so the sensor needs to be calibrated at multiple points. And light source intensity and temperature changes will affect the accuracy of the measurement results.

After many experimental studies and theoretical calculations, it is found that the ratio of scattered light to transmitted light is in a linear relationship with turbidity.

The sensor adopts the ratio of scattered light to transmitted light instead of simple scattered light to measure turbidity, the accuracy and reliability of the sensor are improved, the maintenance is simpler, and the anti-fouling property is enhanced.

How the sensor works:

The working principle of the sensor is: the inside of the sensor is an encapsulated infrared pair tube. When light passes through a certain amount of water, the amount of light transmission depends on the degree of pollution of the water. The more polluted the water, the less light is transmitted.

The light receiving end converts the transmitted light intensity into the corresponding current. By measuring the magnitude of the current at the receiving end, the pollution degree of the water can be calculated.

The turbidity current signal is converted into a 0 V ~ 5 V voltage signal through the resistor R1, and the A/D converter is used for sampling processing, and the single-chip microcomputer can know the current turbidity of the water. The turbidity sensor has 3 pins. In actual use, it is necessary to obtain empirical data on the degree of soiling of clothes through experiments.

Turbidity meter:

The turbidimeter adopts a double-beam optical path and has two highly symmetrical optical and electrical channels, which produce the same induction, and the measurement error remains unchanged, which can be offset in the division circuit, so that the instrument has long-term stability and anti-interference ability;

The water turbidity sensor adopts a linearization circuit to display the measurement results linearly; it adopts special technologies such as temperature compensation, analog division function, and noise elimination, which ensures the high sensitivity and excellent reproducibility of the instrument.

Water turbidity sensor data details: from Google Scholar

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