The Lenterra Flow Sensor (LFS) System from Freeman Technology includes the Lenterra Optical Interrogator (LOI), a Drag Force Flow (DFF) sensor, and a sturdy laptop with bespoke software.

Freeman Technology is the exclusive international distributor of all Lenterra products.

The LFS system offers an in-line, real-time assessment of powder flow, allowing enhancements in process understanding and production efficiency in numerous industries.

Key Features

  • Multi-directional sensitivity
  • Real-time, in-line measurement of material temperature and properties
  • Chemically resistant construction
  • Fiber optic connectivity


  • Improves cycle times
  • Robust Process Analytical Technology (PAT)
  • Improves product quality and consistency
  • Simplifies or expedites scale-up
  • Enhances process understanding
  • Minimizes “out of specification” rework and material
  • Reduces costs associated with resampling, reworks, retesting, etc.
  • Improves compliance

How it Works

The DFF sensor has a hollow pillar fixed on a stationary base, comprising of two optical strain gauges, Fiber Bragg Gratings (FBGs). The LOI is linked to the FBGs through a fiber optic cable and constantly monitors the FBG spectra. When the pillar is deflected by flow, one FBG becomes stretched and the other one is compressed, resulting in a shift in wavelength spectra. A larger deflection causes a bigger shift.

When the probe is inserted into a moving material or powder, the force of the flow causes the DFF sensor to bend. The magnitude of the deflection is constantly determined, and the drag force is quantified in real-time. This is a function of material properties such as size, adhesion, density, and strength, enabling operators to evaluate material properties in-process.

Cross section of a DFF sensor

The technical support from Freeman Technology is super. You can expect responses within 24 hours.

Dr Shau Yen, Senior Fellow, Novartis Pharma AG


  • High Shear Wet Granulation
  • Feeding
  • Drying or spray drying
  • Flow rates in transfer chutes and pipes
  • Blending

Case Study—High Shear Wet Granulation

High Shear Wet Granulation (HSWG) is extensively used in several industries. Effective management of HSWG processes needs an insight into granule evolution and the effect of changing properties.

The DFF sensor provides important information to aid in the formulation and process development, and for control during manufacturing, standard monitoring, and scale-up strategy. The following data shows how the technology can be maximized to monitor a granulation process, allowing users to track granule evolution without disturbing the process.

Benefits of Drag Force Flow (DFF) Sensors

  • Properties of the granulated wet mass can be assessed without stopping the process
  • Measured FPM signal relates to granule densification and wet mass consistency, providing considerably more information than just granule size distribution
  • The effect of process parameters on granule properties (for example, impeller speed/time, water content) can be determined
  • Minor batch-to-batch differences can be identified and computed with similar formulations
  • Each stage of the granulation process can be accurately tracked and used to establish granulation end-point, allowing strong formulation development; process design and control also supports efficient scale-up of wet granulation processes