DirectShear

$6,497$9,447

DirectShear™ Sensors are robust, high-bandwidth, high-resolution, micromachined wall shear stress sensors for subsonic and transonic applications.

This non-intrusive, design delivers an unprecedented degree of precision and accuracy for both mean and fluctuating wall shear stress measurements. This sensor system greatly extends the spatial and temporal resolution capabilities over existing devices, offering exceptional bandwidth and dynamic range.

Originally developed for NASA, the capacitive sensors are now commercially available and are ideal for precise skin friction measurements in wind tunnels. Click here to see how NASA is utilizing these sensors.

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

For high-temperature applications, please see our DirectShear-Optical 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: CS Series Category:

Lead Time and Pricing

Lead Time

12-16 Weeks

Sensor

Sensor Head (+$3,999)

Control Unit

PXI (+$2,199), H2U (+$4,999)

Cable Length

2 meters (+$299), 5 meters (+$349), 10 meters (+$449)

directshear-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

The DirectShear™ sensor heads are micromachined, floating element devices that enable time-resolved, one-dimensional, direct mean and fluctuating wall shear stress measurements.

Features

  • Micromachined floating element shear stress sensor that enables time-resolved, one-dimensional, direct shear stress measurements
  • Compact, robust sensor package for flush mounting
  • Optimized Sensor Control Unit (SCU) for high dynamic range and bandwidth
  • Suite of sensor models for different applications
  • Originally developed for NASA
  • Ability to measure mean and fluctuating quantities
  • Integrated rechargeable lithium-ion battery system minimizes power line noise
  • Multi-pin shielded sensor connector provides supply voltages and carrier signals
  • System status and battery voltage LED indicators

Applications

  • Instrumentation-grade skin friction sensing
  • Aerodynamic drag research
  • Detection of flow separation
  • Wind tunnel instrumentation

Benefits

  • Direct measurement of shear stress — no heat transfer calibration
  • Non-intrusive — minimal flow disturbance
  • Simultaneous mean and fluctuating shear stress measurements
  • High resolution, wide dynamic range, and broad bandwidth
  • Highly accurate, quantitative measurements

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)
  • Also available in multi-sensor 1x4 array package
Model Shear Stress (Pa) Bandwidth (kHz) Sensitivity (mV/Pa) Resolution (mPa) Element Size
CS-0510 10 0.75 100 0.1 2mm x 0.5mm
CS-0110 50 1.5 40 0.1 2mm x 0.4mm
CS-0610 100 2.5 10 1 2mm x 0.4mm
CS-0210 300 5 1 1 1mm x 0.2mm
CS-0310 1000 10 0.3 5 0.5mm x 0.15mm
CS-0410 5000 20 0.08 10 0.5mm x 0.15mm

The following additional components and specifications are recommended for AC and DC testing/calibration with the capacitive 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.

DirectShear-2D

Dual-Axis
from $9,147/system
  • 0-50°C Operating Range
  • Dual-Axis Measurements
  • PXI & Standalone Control Units
  • 2 Sensor Model Options
  • Custom Housings Available

DirectShear-Optical

High Temperature
from $15,498/system
  • 0-400°C Operating Range
  • Single-Axis Measurements
  • Standalone Control Unit
  • 6 Sensor Model Options
  • Custom Housings Available

Related Publications

Characterization of a Fully-Differential Capacitive Wall Shear Stress Sensor for Low-Speed Wind Tunnels

Characteristics of Turbulent Boundary Layer Large Scale Motions using Direct Fluctuating Wall Shear Stress Measurements

Temperature Sensitivity Reduction of a Capacitive Wall Shear Stress Sensor System for Low-Speed Wind Tunnels

Related Projects

MEMS Skin Friction Sensor

Fully-Differential Skin Friction Sensor Hardware and Calibration Method Development

Direct Wall Shear Stress Measurement for Rotor Blades

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 Sensors?

DirectShear Sensors are typically used in low-speed wind tunnel testing applications.

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.

What is the difference between the H2U and PXI control units?

The H2U version is a standalone unit that runs on its own battery powered system and provides location flexibility, but is the larger and more expensive of the two options. The PXI model was developed to provide our customers a minimized overall footprint for the control unit and to take advantage of the PXI chassis form factor and power combined with the possibility to use a PXI-based system for the entire measurement capability.

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.