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 two (2) 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 so that an offline measurement can be made.

Download Specification Sheet (PDF)


  • In-line, real-time measurement
  • Multi-directional sensitivity
  • Chemically resistant construction
  • Fiber-optic connectivity capability


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


Model Number Measurement Range1 Resolution2 Resonance Frequency Pillar Diameter Pillar Length
P-15000-20 ±15 N 15 mN 4,800 Hz 2.77 mm 20 mm
P-11000-40 ±11 N 10 mN 1,800 Hz 4.19 mm 40 mm
P-8000-40 ±8 N 8 mN 1,600 Hz 3.76 mm 40 mm
P-5000-40 ±5 N 5 mN 1,500 Hz 3.4 mm 40 mm
P-4000-40 ±4 N 4 mN 1,300 Hz 3.05 mm 40 mm
P-2500-40 ±2.5 N 3 mN 1,200 Hz 2.77 mm 40 mm
P-1500-40 ±1.5 N 2 mN 1,000 Hz 2.41 mm 40 mm
P-1000-40 ±1 N 1 mN 900 Hz 2.11 mm 40 mm
P-500-40 ±0.5 N 0.5 mN 750 Hz 1.83 mm 40 mm
P-300-40 ±0.3 N 0.3 mN 700 Hz 1.65 mm 40 mm
P-200-40 ±0.2 N 0.25 mN 600 Hz 1.47 mm 40 mm
P-170-80 ±0.17 N 0.17 mN 230 Hz 2.11 mm 80 mm
P-150-40 ±0.15 N 0.2 mN 500 Hz 1.27 mm 40 mm
P-70-40 ±0.07 N 0.1 mN 440 Hz 1.07 mm 40 mm
P-45-80 ±0.045 N 0.1 mN 180 Hz 1.65 mm 80 mm

1 Custom measurement ranges available.

2 When used with a LOI interrogator.