DirectShear-Optical

$15,498

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.

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 (0-400°C) test facilities. Click here to see how NASA is utilizing these sensors.

For typical applications, please see our DirectShear product line.

For vector measurements, please see our DirectShear-2D product line.

Click here to learn more about the Complete Shear Stress Measurement System that leverages additional PXI hardware to create a full measurement solution.

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SKU: OS Series Category:

Lead Time and Pricing

Lead Time

24-30 Weeks

Sensor

Sensor Head (+$7,499)

Control Unit

H2U (+$7,999)

directshear-optical-control-unit-options
WirelessArray Connection Diagram

A Guide to Wall Shear Stress Measurement

Good Data Acquisition Case Study: The IC2 Complete Shear Stress Measurement System

Designed from the ground up for harsh environments, including high-temperature applications.

Features

  • 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 Control Unit for high dynamic range and bandwidth
  • Suite of sensor models for different applications
  • Mean and fluctuating optical wall shear stress measurements
  • Selectable low-noise AC or rechargeable Li-ion battery power source
  • High dynamic range and bandwidth
  • System status and battery voltage LED indicators
  • Rugged, industrial LC Duplex fiber connection
  • Removable shielded sensor cable

Applications

  • Time-resolved, direct mean and fluctuating wall shear stress measurements
  • Differential optical shear stress sensors for subsonic and transonic applications
  • Instrumentation-grade skin friction sensing in high temperatures and harsh environments
  • Aerodynamic drag research
  • Detection of flow separation
  • High-speed wind tunnel testing

Benefits

  • 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
  • Detachable cable assembly
  • 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)
Model Shear Stress (Pa) Bandwidth (kHz) Sensitivity (mV/Pa) Resolution (mPa) Element Size
OS-0510 10 0.8 190 0.1 1.5mm x 0.7mm
OS-0110 50 1.8 40 0.5 1mm x 0.7mm
OS-0610 100 2.5 20 1 1mm x 1mm
OS-0210 300 5 5 2 0.4mm x 0.4mm
OS-0310 1000 10 1.3 50 0.3mm x 0.3mm
OS-0410 5000 20 0.3 50 0.3mm x 0.3mm

The following additional components and specifications are recommended for AC and DC testing/calibration with the optical sensor control unit:

  • RG58 coaxial cable with BNC connectors
  • Data acquisition system (DAQ) – AC/DC measurement
    • Sensing Range: ±1, ±5, ±10V – sensor dependent (see datasheet)
    • Resolution: 18+ bits
    • Sampling frequency: sensor dependent – adequate sample rate and anti-alias filter to support sensor bandwidth
  • Digital multimeter – DC measurement only
    • 6.5 digits with power line cycle (PLC) integration
    • DAQ or PC connection (e.g., GPIB)

Click here to learn more about the Complete Shear Stress Measurement System that leverages additional PXI hardware to create a full measurement solution.

Related Publications

A MEMS optical moiré shear stress sensor for harsh environment applications

Characterization of an Optical Moiré Wall Shear Stress Sensor for Harsh Environments

A miniaturized optical package for wall shear stress measurements in harsh environments

Related Projects

Highly-Resolved Wall-Shear-Stress Measurement in High Speed Flows

A MEMS Floating Element Shear Stress Sensor for Hypersonic Flows

Fiber-Optic Vector Skin Friction Systems for Cryogenic Shear Stress Measurements

Frequently Asked Questions

What are DirectShear sensors?

DirectShear sensors provide a direct measurement of the wall shear stress via MEMS transduction technologies, eliminating the limitations of the indirect methods and vastly improving the accuracy of the measured data, enabling engineers to better understand critical aerodynamic effects and design aircraft to fly more efficiently.

Why is directly measuring wall shear stress important?

Prior to the release of IC2’s DirectShear sensors, wall shear stress was traditionally difficult to measure. Previous methods relied upon indirect approaches by measuring a different fluid property, such as heat transfer rate, and relating it back to shear stress empirically. That process usually requires making several assumptions and carefully controlling the environment, limiting the usefulness of these methods and the accuracy of the resulting data.

What is the typical application for DirectShear-Optical Sensors?

DirectShear-Optical Sensors are typically used in wind tunnel testing applications. Optical models are designed specifically for high-temperature and harsh environments.

What is the operating temperature range for DirectShear Sensors?

DirectShear and DirectShear-2D models are specified for 0-50°C operating temperature. DirectShear-Optical sensors have an operating range of 0-400°C.

How long is the cable coming off the back of the sensor?

The cable is 2m built into the sensor which is not removable. An additional patch cable may be purchased separately to extend the length of the cable.

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 do acceleration forces affect the sensor?

The sensor can survive large accelerations; more than 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 the coherent power between the DirectShear sensor and the accelerometer should be subtracted from the measurement. 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 calibrates the dynamic response of 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 is the sensor typically mounted to the wall of a test section?

The sensor head may be placed in any known angular orientation with respect to the sensing axes. Angular misalignment during installation can result in increased uncertainty due to cross-axis sensitivity. Installation of the sensor head with the alignment key on the upstream side ensures alignment with the critical sensing axis. 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.

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 be used to keep the sensor face covered at all times when not in use. Proper sensor cleaning procedures are outlined in the provided User Manual.