DirectShear - Optical™ Sensor Head

Optical Shear (OS) Series


High-Temperature Wall Shear Stress Instrumentation

Product Description

DirectShear-Optical™ sensors are robust, high-bandwidth shear stress sensors designed from the ground up for harsh environments, including high-temperature applications.  The sensors employ  purely optical transduction,  a silicon/Pyrex micromachined floating element, and a remote optical fiber readout to enable time-resolved one-dimensional, direct shear stress measurements at high temperatures.  

Like the original DirectShear line of sensors, IC2's DirectShear-Optical sensors are capable of both mean and dynamic measurements of wall shear stress over a wide dynamic range and are offered in a range of sensor models to suit different applications.

The optical sensors are now commercially available and are ideal for precision skin friction measurements in high-speed, high-temperature test facilities. Click here to see how NASA is utilizing these sensors.


Control Unit Options:

Add the following to your quote to power, control, and interface with your sensor.


  • Optical micromachined floating element sensor for time-resolved, one-dimensional, direct shear stress measurements in harsh environments
  • Optical gratings for direct transduction of shear stress with remote optical fiber readout
  • Silicon/Pyrex sensor structure for high-temperature environments (up to 400°C continuous)
  • Optimized Sensor Control Unit (SCU) for high dynamic range and bandwidth
  • Suite of sensor models for different applications


  • Instrumentation-grade skin friction sensing in high temperatures and harsh environments
  • Aerodynamic drag research
  • Detection of flow separation
  • High-speed wind tunnel testing


  • Direct measurement of shear stress
  • Harsh environment capable
  • Non-intrusive - minimal flow disturbance
  • High resolution, dynamic range and bandwidth
  • Immune to EMI

Sensor Head Housing Details

  • Non-intrusive — backside contacts for minimal flow disturbance
  • Standard stainless steel cylindrical housings available with or without shoulder and key alignment and detachable cable
  • Multiple sensor head form factors, materials and finishes available to meet installation requirements.
  • Custom housings/materials available
  • Suite of 6 sensor models available for different applications (see Specifications table)

What is the typical application for DirectShear Sensors?

DirectShear Sensors are typically used in wind tunnel testing applications. 

How do acceleration forces affect the sensor?

The sensor can survive large accelerations, >200g. The floating element's small size and mass limit any significant inertial loads. However, accelerations will affect the output of the sensor. To account for acceleration, an additional accelerometer should be placed near the DirectShear sensor and subtract the coherent power between the DirectShear sensor and the accelerometer. IC2 provides the acceleration sensitivity data in the calibration packet included with each sensor purchase. IC2 is currently working on a future generation of the sensor that will compensate for acceleration automatically. Please contact IC2 for additional information regarding acceleration compensation.

Are DirectShear sensors NIST traceable?

IC2 currently dynamically calibrates its sensors in an acoustic plane wave tube and is working on a new Mean Shear Facility for improved calibration capabilities. DirectShear sensor calibrations are not NIST traceable because no standard yet exists. Our DirectShear sensor is the first of its kind on the market that makes this measurement. It is in our purview and we have had discussions with NIST about creating a standard.

How cautious should I be when handling the sensor?

The sensing element (the front face) is extremely fragile. Any physical contact with the exposed sensing element can cause damage to the sensor. A protective cap is provided for handling purposes and should remain covered at all times when not in use. Proper sensor cleaning procedures are outlined in the provided User Manual.

What are the operating temperature ranges for DirectShear - Optical sensors?

Optical models are designed for more extreme environments and can withstand temperatures from 0-400°C.

Does each sensor need its own control unit?

Yes. Each sensor requires a dedicated control unit and each unit supports a single sensor at a time; however, multiple sensors can be paired with a single control unit in cases where spares or different sensor types are desired. Engineering services are available for customers who desire custom configurations of control units to support multiple sensors.

How is the sensor typically mounted to the wall of a test section?

The sensor head should be aligned such that the deflection of the sensing element corresponds to the direction of flow (long axis of the sensing element is in the streamwise direction). While angular misalignment during installation can decrease the overall sensitivity, the reduction in sensitivity is minor at small angles (<15°). Installation of the sensor head with the alignment key on the upstream side ensures that the sensor is properly oriented. The sensor head should be inserted until the surface of the sensor head is flush with the facility wall. Proper design of the sensor installation port will provide repeatable installation depths and alignment via use of the shoulder and alignment key on the sensor head. Please contact IC2 for support with sensor installation.

Are DirectShear - Optical Sensors ITAR controlled?

These sensors are not ITAR items, but may be subject to the EAR in certain configurations.