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.
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
Applications
Instrumentation-grade skin friction sensing
Aerodynamic drag research
Detection of flow separation
Wind tunnel instrumentation
The DirectShear™ sensor heads are micromachined, floating element devices that enable time-resolved, one-dimensional, direct mean and fluctuating wall shear stress measurements.
Benefits
Direct measurement of shear stress — no heat transfer calibration
Non-intrusive — minimal flow disturbance
Simultaneous mean and fluctuating shear stress measurements
High resolution, dynamic range and 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 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-Capacitive Sensors?
DirectShear-Capacitive Sensors are typically used in low-speed 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 is the operating temperature range for DirectShear-Capacitive Sensors?
Capacitive models are specified for 0-50°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 - Capactive Sensors ITAR controlled?
These sensors are not ITAR items. They are also not subject to the EAR.
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