Low Range Turbidity Probe for HI5x0 Controller - HI7660-28xx

What is the HI7660-28 probe?

The HI7660-28 is a nephelometric measuring device engineered to detect low turbidity levels in water with exceptional precision. This digital probe is compatible with Hanna Instruments® universal HI510 and HI520 controllers and is designed for installation in water treatment systems where reliable monitoring is critical. Using an infrared optical system and factory calibration, the probe ensures long-term, stable performance with minimal maintenance. The HI7660-28 fully complies with ISO 7027 - EN 27027 international standards, making it a regulation-ready solution for process control in municipal, industrial, and environmental sectors.

Operating Principle

The HI7660-28 operates based on nephelometric measurement—detecting light scattered by suspended particles in a water sample. An infrared LED generates a light beam that passes through an optical window into the sample. Suspended particles scatter part of the light, which is then detected at a 90-degree angle by an internal photodiode. The scattered light is converted into an electrical signal proportional to the turbidity level, expressed in FNU (Formazin Nephelometric Units). This configuration enables accurate readings even at very low turbidity levels, making it especially suitable for sensitive applications like drinking water monitoring or evaluating filtration efficiency.

Recommended Applications

The HI7660-28 is suitable for all settings where continuous, precise turbidity monitoring is required. It is particularly recommended for use in drinking water treatment plants, where turbidity is a key indicator of safety and quality. It is also used in wastewater monitoring, both municipal and industrial, as well as in desalination systems. Furthermore, it serves as a reliable tool for environmental monitoring where real-time detection of changes in water quality is essential.

Accurate and Reliable Measurements

Thanks to its optical design and high-quality components, the HI7660-28 delivers extremely accurate measurements across a wide range. It covers a measurement range from 0.000 to 400.0 FNU, with resolution ranging from 0.001 FNU at the lower end to 0.1 FNU at higher levels. Accuracy is maintained throughout the range, aided by automatic temperature compensation: the probe includes an internal temperature sensor that adjusts the reading based on the sample temperature, ensuring correct values even under changing environmental conditions.

Smart Calibration

Each HI7660-28 probe is factory-calibrated with preset parameters including zero and slope of the calibration curve. However, manual user calibration is also possible, with one-point or two-point options for finer adjustment of slope and offset. Calibration data is stored directly within the probe and includes date, time, standard type used, and calibration coefficients. This ensures full traceability and minimizes the need for frequent recalibration. Calibration timeout is user-configurable from 1 to 99 days or can be disabled entirely, depending on operational requirements.

Rugged, Versatile, and Ready for Integration

Built with a robust PVC body, the HI7660-28 is made to withstand demanding environmental conditions. With IP68 protection, it is fully waterproof and suitable for long-term immersion. It can operate at pressures up to 6 bar at room temperature (25 °C) and up to 3 bar at 50 °C. Available with cable lengths of 2, 5, or 10 meters, it can be installed in a variety of settings. Digital communication is handled via an RS485 interface using the MODBUS RTU protocol, ensuring compatibility with most industrial automation systems.

Flow Cell Installation

For low-turbidity applications, it is recommended to install the HI7660-28 probe in a pressurized flow cell, such as the HI7676602. This accessory is essential for eliminating ambient light interference, maintaining stable sample pressure, and reducing effects like degassing, which can compromise measurement reliability. The flow cell comes complete with a wall-mount bracket, probe adapter with o-ring, inlet and outlet tubing, and a locking collar for secure installation.

Specifications