The HI7660-28 nephelometric turbidity probes are engineered for compatibility with the Hanna Instruments® HI510 or HI520 Universal Process Controllers. Designed to deliver accurate low-level turbidity measurements, the system follows the nephelometric method as defined by ISO 7027 (EN 27027).

Each probe features a built-in temperature sensor that continuously monitors water temperature and compensates for temperature-induced signal variations within a range of 0 to 50 °C (32 to 122 °F). The controller displays both turbidity and temperature readings concurrently.

Turbidity plays a vital role in assessing water quality and filtration performance. This system is well-suited for a variety of applications, including drinking water production, municipal and industrial water treatment, desalination processes, and ongoing water quality assessment.

For most low-level turbidity applications, the HI7660-28 probe is installed within a pressurized flow cell. The HI7676602 flow cell is specifically designed to shield the sensor from ambient light and preserve sample pressure. This setup helps reduce sample out-gassing—an issue that frequently leads to inaccuracies in turbidity readings.

Main feature points

• Digital probe stores model, firmware version, and serial number
• Built-in temperature sensor for measurement and compensation
• Stored calibration data includes: calibration date and time, turbidity calibration standard, offset, and slope
• ISO 7027 sensors use a near-infrared light-emitting diode (LED) to eliminate color interference
• Factory-calibrated turbidity probe
• Adheres to ISO 7027 – EN 27027 standards

Principle of operation

Turbidity refers to the cloudiness or haziness of water caused by suspended particles. The HI7660-28 is an optical probe that measures turbidity in compliance with ISO 7027 – EN 27027 standards, with results expressed in Formazin Nephelometric Units (FNU).

An infrared light beam is emitted through an optical window into the water sample. Suspended particles scatter the light, and the intensity of light scattered at a 90° angle is detected through a second window. This scattered light is then converted into an electrical signal proportional to the turbidity of the sample or standard.