DFF provides in-line, real-time measurement of shear or drag force in mixing and processing operations.

A highly promising PAT tool – continuous in-line flow monitoring eliminates guesswork and the need for costly, time-consuming offline measuring.

In 2012, Lenterra introduced a breakthrough sensor product that offers in-line, real-time measurement of flow forces in powders, multi-phase, chemically aggressive and complex flows such as those realized in High Shear Wet Granulation (HSWG), food processing, and other industrial applications.

DFF is a hollow needle mounted on a stationary base – minute deflection of the needle is detected by optical strain gauges incorporated within the needle. DFF provides information of densification, viscosity or granularity of the flow along with a number of other metrics depending on the application.

Using lightwave communication instead of electrical current and glass fiber instead of copper wire, the sensors are nonconductive, electrically and chemically passive, and immune to electromagnetic interference.



“Lenterra’s Drag Force pillar sensors is the first commercial system of its kind to provide continuous, real time measurement from which flow velocity, flow rate and/or viscosity can be derived. The pillar sensor will provide visibility into – and real-time information on – processing conditions inside high-shear wet granulators.” – Pharmaceutical Processing Magazine.


Mounted on a stationary base, the thin DFF “needle” contains several fiber optic gages which are connected to a controller via a fiber-optic cable.

When immersed in a liquid, the DFF bends under the force of the flow measuring the drag force.
The amount of bending is measured in-line in real-time allowing the user to determine immediately whether or not any adjustments are necessary eliminating the need to stop the flow operation for an offline measurement. More…


  • In-line, real-time measurement
  • Multi-directional sensitivity
  • Small size – minimal interaction with flow
  • High measurement rate
  • Measuring force and temperature
  • Chemically resistant construction
  • No electrical parts – no ignition hazard
  • Fiber-optic connectivity


  • Reduce costs (reworks, resample, retesting, etc)
  • Reduce cycle times (operational efficiency)
  • Improve customer service (product availability)
  • Reduce/eliminate deviations
  • Improve compliance
  • Improve quality assurance
  • Improve capacity utilization
  • Reduce inventory levels

Standard Models

Model Number Measurement Range1 Resolution2 Pillar Diameter Pillar Length
S-15000-30 ±15 N 5 mN 3.2 mm 30 mm
S-4000-40 ±4 N 1.3 mN 2.8 mm 40 mm
S-300-40 ±0.3 N 0.3 mN 1.27 mm 40 mm

1 Custom measurement ranges available.

2 When used with an LOI interrogator.