Online COD detection sensor

1Online COD detection sensorworking principle

Many organic compounds dissolved in water have an absorption effect on ultraviolet light. Therefore, by measuring the degree of absorption of these organic compounds by 254nm wavelength ultraviolet light, the content of dissolved organic pollutants in water can be accurately measured. The COD-308 online COD sensor uses two light sources, one ultraviolet light for measuring COD content in water and one reference light for measuring water turbidity. In addition, a specific algorithm is used to compensate for the attenuation of the light path and to some extent eliminate the interference of particulate suspended matter impurities, thereby achieving more stable and reliable measurement.

Product Features:

No need for reagents, no pollution, economical and environmentally friendly

Compact size, easier installation, and online uninterrupted water quality monitoring

L can measure parameters such as COD, turbidity, and temperature

Automatically compensate for turbidity interference

Equipped with a cleaning brush to prevent biological attachment

Small drift, fast response, and more accurate measurement

Even with long-term monitoring, it still has*Excellent stability

L maintenance free, long service life, low usage cost

Digital sensor, RS-485 interface, Modbus/RTU protocol

Low power design, anti-interference design

2、 Technical performance and specifications

1. Technical parameters

2. Dimensional drawing

Note: The sensor connector is a male M16-5 core waterproof connector

3、 Installation and electrical connections

1. Installation

When hanging sensors, it is important to avoid collisions with walls or other water facilities caused by water flow. If the water flow is very fast, please fix the sensor.

Install sensors at a depth of no more than 2 meters above the water surface.

Considering the fluctuation of water level, it is possible to submerge the sensorThe lowest water level is below 30cm.

The sensor is placed in a location where there are no bubbles in the water.

Note: It is recommended to install a cable protection sleeve outside the sensor cable. The sensor can be placed in any direction in the water. It is recommended to place the sensor horizontally and fix it firmly, with the measurement area facing the direction of the water flow.

2. Electrical connection

The cable is a 4-core twisted pair shielded wire, and the line sequence is defined as follows:

Red wire - power cord (12-24VDC)

Black wire - Ground wire (GND)

Blue line -485A

White line -485B

Before powering on, carefully check the wiring sequence to avoid unnecessary losses caused by wiring errors.

Wiring instructions: Considering that cables are immersed in water (including seawater) or exposed to air for a long time, waterproof treatment is required at all wiring points, and user cables should have a certain degree of corrosion resistance.

4Online COD detection sensormaintenance and upkeep

1. Maintain schedule and methods

1.1 Maintenance Schedule

To ensure accurate measurement, cleaning is important. Regular cleaning of sensors helps maintain data stability.

Note: The maintenance frequency in the above table is only a suggestion. Maintenance personnel should clean the sensor according to its actual usage.

1.2 Maintenance Methods

1) Outer surface of sensor: Clean the outer surface of the sensor with tap water. If there are still debris residue, wipe it with a damp soft cloth. For stubborn dirt, add some household detergent to tap water to clean it.

2) Check the cable of the sensor: During normal operation, the cable should not be tightened, otherwise it may cause the internal wires of the cable to break, causing the sensor to malfunction.

3) Check if the measurement window of the sensor is dirty and if the cleaning brush is functioning properly.

4) Check if the cleaning brush of the sensor is damaged.

5) After continuous use for 18 months, it is necessary to return to the factory to replace the dynamic sealing device.

1.3 Precautions

Sensors contain sensitive optical and electronic components. Ensure that the sensor is not subjected to severe mechanical impact. There are no components inside the sensor that require user maintenance.

2. Calibration of sensors

2.1 Turbidity calibration

1) Zero point calibration: Use a larger beaker to measure an appropriate amount of zero turbidity liquid, place the sensor vertically in the solution, and wait for 3-5 minutes for the value to stabilize before performing zero point calibration. Refer to the appendix for instructions.

2) Slope calibration: Place the sensor in a 100NTU standard solution and wait for 3-5 minutes for the value to stabilize before performing slope calibration. Refer to the appendix for instructions.

2.2 COD calibration

1) KHP (potassium hydrogen phthalate, C8H5KO4) is a commonly used chemical reagent that can be used to prepare COD standard solutions.

2) Prepare standard solution

① Accurately weigh 0.8503 g of KHP and place it in a 1000mL flask. Pour distilled water or deionized water to the highest mark This solution is a COD solution with a concentration of 1000mg/L.

② Take 100 mL of this solution and inject it into a flask with a capacity of 1000 mL, then fill it with distilled water or deionized water to the highest mark. The COD concentration after shaking is 100mg/L. Prepare a solution with a concentration of 20mg/L using the same method.

③ Store this concentrated standard solution in a black glass bottle (step 2.1) and store it at low temperature to prevent its decomposition. The diluted standard solution (step 2.2) needs to be used within 24 hours after preparation.

3) Calibration (2-point calibration)

a. Calibration of the range of 0-200mg/L

① Place the sensor in a 5mg/L COD solution and confirm that all optical paths are submerged underwater>2cm without bubbles. Perform zero calibration according to the instructions in the appendix.

② Place the sensor in a 200mg/L COD solution and perform slope calibration according to the instructions in the appendix.

b. Calibration of the range of 0-500mg/L

① Place the sensor in a 20mg/L COD solution and confirm that all optical paths are submerged underwater>2cm without bubbles. Perform zero calibration according to the instructions in the appendix.

② Place the sensor in a 400mg/L COD solution and perform slope calibration according to the instructions in the appendix.

Note: 1. KHP has a carcinogenic risk, please wear gloves during operation to avoid skin contact.

When calibrating, first calibrate the temperature, then calibrate the turbidity, and finally calibrate the COD.

If there is no change in the sensor value within 3 minutes after calibrating the slope, power off and then power on again.

3. Precautions

Avoid exposing the sensor to sunlight

Please do not touch the sensor measurement area with your hands

Avoid attaching bubbles to the sensor surface during measurement and calibration

Avoid applying any mechanical stress (pressure, scratches, etc.) directly to the sensor during use

4. Common problems and countermeasures

5、 Quality and Service

1. Quality assurance

The quality inspection department has standardized inspection procedures, advanced and complete testing equipment and methods, and strictly follows the procedures for inspection. It conducts 72 hour aging and stability tests on products to prevent any unqualified products from leaving the factory.

The receiving party shall directly return batches of products with a defect rate of 2%, and all costs incurred shall be borne by the supplier. The testing standards refer to the product specifications provided by the supplier.

Ensure the quantity of goods and the speed of shipment.

2. Accessories and spare parts

This product includes:

1 sensor

1 copy of instruction manual

1 certificate of conformity

1 cable (5 meters)

3. After sales service commitment

Our company provides after-sales service for this machine within one year from the date of sale, but does not include damage caused by improper use. If repair or adjustment is needed, please send it back, but the shipping cost will be borne by yourself. When returning, please ensure that the packaging is good to avoid damage during transportation. Our company will repair the damaged equipment free of charge.

Appendix Data Communication

1. Data format

The default data format for Modbus communication is 9600 n、 8. 1 (baud rate 9600bps, 1 start bit, 8 data bits, no checksum, 1 stop bit).

2. Information frame format (xx represents one byte)

a) Read data instruction frame

06 03 xx xx xx xx xx xx

Address Function Code Register Starting Address Register Quantity CRC Check Code (Low Byte First)

b) Read data response frame

06 03 xx xx……xx xx xx

Address Function Code Byte Count Response Data CRC Check Code (Low Byte First)

c) Write data instruction frame

06 06 xx xx xx xx xx xx

Address Function Code Register Address Write Data CRC Check Code (Low Byte First)

d) Write data response frame

06 06 xx xx xx xx xx xx

Address Function Code Register Address Write Data CRC Check Code (Low Byte First)

3. Register address

4. Command Examples

a) Measurement instruction:

Function: Read the COD and temperature values of the sensor; The unit of COD value is mg/L, and the unit of temperature is ℃.

Request frame: 06 03 00 00 04 45 BE

Response frame: 06 03 08 03 62 00 01 00 B9 00 01 A1 95

Reading example:

For example, COD value 03 62 represents the hexadecimal reading COD value, 00 01 represents COD with one decimal point, converted to a decimal value of 86.6.

The temperature value 00 B9 represents the hexadecimal reading temperature value, and 00 01 represents the temperature value with one decimal point, converted to a decimal value of 18.5 ℃.

b) Calibration instruction:

temperature calibration

Function: Calibrate sensor temperature at 25.8 ℃; Temperature calibration should be performed after the temperature has stabilized for a period of time.

Request frame: 06 06 10 01 02 0D 29

Response frame: 06 06 10 01 02 0D 29

Turbidity zero calibration

Function: Set the turbidity zero calibration value of the sensor; Zero point calibration is performed in water with zero turbidity.

Request frame: 06 06 10 20 00 00 8D 77

Response frame: 06 06 10 20 00 8D 77

Turbidity slope calibration

Function: Set the turbidity slope calibration value of the sensor; Command for calibrating slope in 100NTU solution:

Request frame: 06 06 10 24 03 E8 CC 08

Response frame: 06 06 10 24 03 E8 CC 08

COD zero calibration (taking the range of 0-500mg/L as an example)

Function: Set the COD zero calibration value of the sensor; Command for calibrating zero point in 20mg/L solution:

Request frame: 06 06 10 00 C8 8D 2B

Response frame: 06 06 10 00 C8 8D 2B

COD slope calibration (taking the range of 0-500mg/L as an example)

Function: Set the COD slope calibration value of the sensor; Command for calibrating slope in 400mg/L solution:

Request frame: 06 06 10 04 0F A0 C8 F4

Response frame: 06 06 10 04 0F A0 C8 F4

c) Change device ID address:

Function: Change the Modbus device address of the sensor.

Change sensor address 06 to 01, as shown in the following example:

Request frame: 06 06 20 02 00 01 E3 BD

Response frame: 06 06 20 02 00 01 E3 BD

5. Error response

If the sensor cannot execute the upper computer command correctly, it will return the following format information:

a) CODE: 01- Function code incorrect

03- Data Error

b) COM: Received Function Code