The turbidity of water refers to the degree of turbidity caused by suspended substances such as silt, clay, organic matter, plankton and microorganisms contained in the water. Industrial-grade turbidity sensors or turbidity meters are expensive, and the cost is too high in the design of electronic products. The sensor uses optical principles to comprehensively judge the turbidity through the light transmittance and scattering rate in the solution. Inside the sensor is an infrared tube. When light passes through a certain amount of water, the amount of light transmission depends on the degree of dirtiness of the water. The dirtier the water, the less light it transmits. Light The receiving end converts the intensity of the transmitted light to the corresponding current size. The transmitted light is more and the current is larger. On the contrary, the transmitted light is less and the current is smaller.
The turbidity sensor module converts the current signal output by the sensor into a voltage signal, and performs AD conversion data processing through the single-chip microcomputer. The remodeling module has analog and digital output interfaces.
Module introduction and pin definition:
The composition of the turbidity sensor module is shown below. The module is connected to the turbidity sensor through the 3Pin XH-2.54 connector. Adjust the knob of 10K blue potentiometer to adjust the trigger threshold of digital output.
The module pin definitions are as follows:
- VCC: Positive supply voltage, 5V
- AO: analog signal output, output voltage range 0~5V
- DO: digital signal output is less than the set value and outputs high level; greater than the set value and outputs low level
- GND: negative supply voltage
- Working voltage: 5.0V DC
- Working current: 40mA (MAX)
- Response time: <500ms
- Insulation resistance: 100MΩ (Min)
- output method: Analog output: 0~4.5V;
- Digital output: high/low level signal
- Operating temperature: -20℃~90℃
- Module size: 38.6mm*22.1mm
Introduction of supporting turbidity sensor:
The turbidity sensor model of this sensor module is TSW-30, as shown in the following figure.
The technical parameters @ (25℃)
(1) Application circuit block diagram, The recommended application circuit block diagram is shown below.
(2) Standard curve and temperature calibration formula
The relationship between sensor module output voltage and turbidity is shown in the figure below.
The turbidity value and the module output voltage satisfy the following relationship:
TU = -865 .68xU+K
Temperature correction formula:
The above formula is the voltage difference caused by temperature change; T is the current measured temperature value.
(4) Calibration method
Due to individual differences in turbidity sensors, ambient light, or no temperature compensation. To get more refinedThe exact turbidity value must be calibrated before measurement. The specific operation method is introduced as follows.
Step 1: Install the turbidity sensor to power the sensor module. Use 0NTU standard solution (Or close to 0NTU of purified water or distilled water) for calibration;
According to the above four turbidity solutions, the turbidity level is divided into four levels, the specific level is shown in the table below
Note: The above grading method is only for illustration, the specific parameter grading threshold can be set according to specific needs
(6) Using digital signals
Select the contrast solution with a specific degree of turbidity, and adjust the potentiometer knob to the position where the D1 indicator just turns on (that is, the critical value of high and low levels) to complete the threshold setting. The DO port of the sensor module is connected to the I/O port of the single-chip microcomputer to judge the output signal or to connect an external drive circuit to drive other devices to operate.
1. The top of the turbidity sensor is not waterproof. It is forbidden to throw the turbidity sensor completely into the water when using it. The water surface must not cross the connection between the top cover and the housing. Ingress of water into the sensor will cause the sensor to burn out.
2. The wavelength range of light received by the sensor photodiode is (500~1050nm). The wavelength of sunlight or daylight light line will affect the reception of the sensor photoresistor and affect the measurement output. Direct sunlight or light will increase the measurement error of the sensor. When using the sensor, direct sunlight or light should be avoided.
3. The sensor head housing must be kept clean to avoid inaccurate measurement caused by contaminants.