In-line, real-time direct measurement of wall shear stress

In 2012, Lenterra introduced the first instrument capable of direct measurement of wall-shear forces – without process flow interruption.

Known as the RealShear™ sensor, it also allows operators to measure fluid viscosity changes in a mixing process, and calculate the flow rate.

Lenterra’s RealShear™ Wall Shear Stress Sensor mounts flush with a pipe or vessel wall enabling direct measurement of wall shear stress, flow rate and viscosity of liquids during flowing or mixing.

The main benefit for users is that measurements can be taken without the need to disrupt the mixing process which allows for “on-the-fly” scaling up of mixing processes or mixing process adjustments as required.


Mounted flush with a pipe or vessel wall or rotor-stator workhead, the RealShear Wall Stress Sensor provides in-line measurement of process flow of liquids in real-time – without any disruption of process flow.

The Lenterra sensor relies on a floating element that is installed flush to the vessel wall, and attached to a cantilever beam that deflects in response to shear stress as fluid flows across its surface.

The cantilever transmits the shear force to a fiber-optic microresonator which has its resonance centered at a particular light wavelength.

Shear stress felt by the cantilever places strain on the optical resonator, which causes a shift in the resonant wavelength. The shift is proportional to the shear stress.

Because the RealShear sensors are optically based, they are unaffected by electromagnetic interference and are explosion safe.

Fast, continuous measurement of flow, viscosity and multiphase flow characteristics are provided via an LOI Optical Interrogator or LOC-F Optical Controller.


  • In-line, real-time measurement
  • Bi-directional sensitivity
  • Chemically resistant construction
  • Fiber-optic connectivity capability
  • Two footprint sizes
  • High measurement rate
  • Operation in wide range of temperatures
  • Complete sensor measurement system


  • 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 Nominal Resonance Frequency
F-1003 ±100 Pa 0.2 Pa 80 Hz
F-4003 ±400 Pa 0.7 Pa 150 Hz
F-1K ±1000 Pa 1.5 Pa 230 Hz
F-5K ±5 kPa 6 Pa 450 Hz
F-25K ±25 kPa 20 Pa 820 Hz
M-2003 ±200 Pa 0.4 Pa 70 Hz
M-6003 ±600 Pa 1.6 Pa 80 Hz
M-2K ±2000 Pa 5 Pa 150 Hz
M-5K ±5 kPa 11 Pa 220 Hz
M-25K ±25 kPa 40 Pa 440 Hz
M-100K ±100 kPa 80 Pa 900 Hz
1 Custom measurement ranges available.
2 When used with a LOI interrogator.
3 Sensor with and below ±600 Pa measurement range are particularly sensitive to vibration and sensor orientation effects.