Online Turbidity Sensor

I. Working Principle

The HD-DJ9 scattered-light turbidity sensor determines the concentration of particles in a liquid by measuring light scattering. A light source illuminates the liquid and the intensity of the light scattered at different angles is measured. The sensor uses the 90° scattered-light method, processes the acquired signal linearly and applies a temperature compensation algorithm to output the turbidity value.

II. Key Features

1. 90° scattered-light method with linear signal processing and temperature compensation.

2. Measuring range 0–1000 NTU by default, with 0–40 NTU and 0–3000 NTU available on request.

3. Resolution of 0.1 NTU and accuracy of ±1%.

4. RS485 (Modbus/RTU) output.

5. Compact body, low power consumption (0.2 W at 12 V) and IP68 protection.

6. Two-point calibration for reliable long-term accuracy.

III. Technical Parameters

IV. Installation and Wiring

Do not install the sensor upside down or horizontally; install it at an angle of at least 15° to the horizontal. The measuring port must be at least 5 cm from the container wall on both sides and 10 cm above the bottom.

The cable is a 5-core shielded cable: red - power supply, black - ground, green - RS485-A, white - RS485-B.

V. Maintenance and Care

If the sensor needs cleaning, use warm water with a small amount of detergent.

Avoid strong vibration, which may damage the front optical glass, and never scrape it with hard objects.

VI. Calibration

The sensor is closely calibrated at the factory and normally requires no user calibration. If user calibration has been performed, the factory settings can be restored with the appropriate command.

Zero-point calibration: place the sensor in a non-transparent container filled with distilled or purified water, keeping the measuring port at least 5 cm from the wall and 10 cm above the bottom; after 30 seconds, when the value is stable, perform zero-point calibration according to the communication instructions.

Slope calibration: use a solution of known turbidity (higher than 20% of the range) in a non-transparent container under the same positioning conditions; after 30 seconds, when the value is stable, perform slope calibration according to the communication instructions.