Manual for 4690 Series

4690 Series Turbidity Sensor - Operation Summary

The 4690 Series Turbidity Sensor is a robust instrument designed for accurate and reliable measurement of turbidity in water. It features dry standard verification and automatic cleaning capabilities for simplified maintenance. The sensor is intended for use with the ABB AWT420 dual-input transmitter.

Key Operational Aspects:

• Installation: Proper siting is crucial, requiring adequate clearance and accessibility for maintenance. Avoid direct sunlight. Ensure the sensor is installed within 5° of its vertical axis and connect sample inlet, drain, and outlet tubes accordingly. A de-bubbler is available for eliminating gas bubbles that can affect readings.
• Flow Rate: Maintain a minimum flow rate of 0.5 L/min to prevent solids settling, not exceeding 1.5 L/min.
• Calibration: The system utilizes a dry secondary calibration standard for routine verification, minimizing the need for chemical standards. Primary standards are used for initial calibration or to verify secondary standards.
• Maintenance: Includes scheduled tasks like wiper blade replacement (quarterly) and LED light source replacement (every 5 years). The flow chamber and optical windows require cleaning, with automatic frequency determined by plant experience or manual cleaning for clean water.
• Fault Finding: Addresses unstable or erratic readings by checking for air bubbles or accumulated solids. Intermittent spikes are typically caused by bubbles passing through the light path.