Hefer TU Series Online Turbidity Sensors

The Hefer TU series is a family of online turbidity instruments that use the infrared nephelometric method (ISO 7027 / EN 27027): the TU-311, TU-321 and TU-341 sensors with an isolated 4-20 mA output, and the TU/TSS-3000C integrated analyzer that reads 0-4,000 NTU or 0-10,000 mg/L TSS. As the Hefer distributor in Turkey, Mikron Proses (Üsküdar, Istanbul) supplies, installs and commissions these turbidity sensors, TU-410 flow cells and TU/TSS-3000C analyzers.

Hefer offers two measuring architectures. The TU-311 / TU-341 is a loop sensor that connects to an existing controller or PLC through its 4-20 mA output, while the TU/TSS-3000C is an integrated online analyzer with its own display and controller.

TU-311 family: one body, three variants

The family works on the nephelometric principle with an infrared light source. The TU-311 is the base model for sensitive measurement in the low range (0-4 / 40 / 400 NTU); it works up to 6 bar. The TU-341 shares the same body family and is built for more turbid streams in the high range (0-100 / 1,000 / 10,000 NTU). The TU-321 has the same measuring range as the TU-311 and adds a nozzle that cleans the sensor with compressed air; this lowers the working pressure to 1 bar and makes the body slightly larger (165 mm × 60 mm). It helps in applications where the sensor surface fouls often. All three variants connect to a PLC or data logger through the isolated 4-20 mA current loop, and the TU-311 and TU-321 also have an RS485 digital output. For flow cell installations the TU-410 flow cell is used, with an adjustable 0.2-25 L/h sample flow and an air-operated drain valve.

Model	Range	Output	Notes
TU-311	0-4 / 40 / 400 NTU (0-1 / 10 / 100 mg/L)	Isolated 4-20 mA; RS485	Up to 6 bar; body 143 mm × 40 mm
TU-341	0-100 / 1,000 / 10,000 NTU	Isolated 4-20 mA	Same body as the TU-311, higher range
TU-321	Same as the TU-311	Isolated 4-20 mA; RS485	Compressed-air autoclean nozzle; up to 1 bar; body 165 mm × 60 mm
TU/TSS-3000C	0-4,000 NTU / 0-10,000 mg/L TSS	Isolated 4-20 mA	Auto-ranging; ‘clean sensor’ alarm; submersible or flow cell

Sources: Hefer datasheets for the TU-311 / TU-341, the TU-311 / TU-321 probes and the TU/TSS-3000C. Where the datasheets describe the housing differently (PVC or Delrin), the specifications above list both.

TU/TSS-3000C integrated analyzer

The TU/TSS-3000C works on the same nephelometric principle but combines the display, the controller and fouling compensation in one unit. It switches between ranges automatically across 0-4,000 NTU / 0-10,000 mg/L TSS, detects dirt on the sensor surface and shows a “clean sensor” message, and it can be supplied with an automatic cleaning system on request. It can be installed as a submersible sensor or in a flow cell.

Choosing a turbidity architecture

Whether a separate sensor with a controller or an integrated analyzer suits your process, and which range, depends on the turbidity level to be measured and on the automation you already have. Mikron Proses can review this together with you. For the background on measurement methods, see the guides on online turbidimeters and drinking water turbidity.

Related pages

• Hefer brand page
• Hefer OD-3000C dissolved oxygen analyzer
• Hefer CLO-3000C chlorine dioxide analyzer
• Hefer 2030 series transmitters
• Online measurement and automation systems