Pressure sensors suit wind tunnel applications

Scanivalve produces miniature pressure scanning devices that are fast, efficient and affordable.

Calibration Dynamics is a UK supplier of wind tunnel instrumentation and test equipment.

Wind tunnel testing enables the manufacturer to model a design as closely to working conditions as possible, but in a controlled environment.

This would be virtually impossible to do in a real life, full-scale situation where conditions are so turbulent and size constraints exist.

In a wind tunnel air is blown at the desired speed over the model of the object being tested as opposed to the model moving through the air.

Therefore the real-life scenario is recreated but with all flow conditions under the complete control of the engineer thus producing accurate, traceable and reliable data.

The method is used extensively in the fields of aerospace, automotive and building research and development.

In the aerospace field wind tunnel testing is used when engineers need to acquire information for use in aerodynamic research, stress analysis, aerodynamic lift, stability, control and fuel efficiency.

It is used in the automotive industry predominantly by motorsport teams.

In this sport it is paramount that engineers are continually improving the aerodynamic efficiency of the model and accurate, fast, surface pressure measurement provides important data to determine down force, frictional drag reduction and lift decrease.

It is also used to gather data on pressure distribution which is required to understand the cars dynamics and increase aerodynamic performance.

Many motorsport teams use low-speed closed-loop tunnels which can produce air speeds in the region of 10 - 80m/second and combine this with rolling road technology to ensure that the effects of turbulence with rolling wheels are taken into account.

The majority of testing is done using a scale model and pressure scanning equipment is placed inside the model to test what effect changes in structure has upon performance.

In the past these data collecting systems were large, expensive and tricky to operate.

However, working from their purpose built base in Spokane, Washington, Scanivalve produce miniature pressure scanning devices that are fast, efficient and affordable.

The company has created one of the smallest, most compact and modular pressure scanning systems available.

This equipment is used for obtaining aerodynamic test data in research and development applications and is already used extensively in the fields of motorsport and aerospace dynamics.

These products are particularly suited to in-model testing where space is at a premium and they provide USB communications so are compatible with the average PC thus making them appeal to universities and research facilities.

The model RAD3200 Remote A/D interfaces ZOC pressure scanners to a PC.

Its modular design allows up to 8 A/D (16 bit) modules to be plugged into one Radbase.

The Radbase is comparable in size to an average wrist watch.

It is typically located within the model under test itself or other space limited locations in close proximity to the ZOC pressure scanners.

The output of the RAD3200 is A/D counts transmitted via a single small diameter USB cable to the users PC where EU conversions are then performed.

Each A/D supports one, 16, 32, 64 or 128 channel ZOC pressure scanner or one ZOC electrical input module.

Thus for small models with low-pressure channel requirements, the RAD can be very small.

A feature of the system is that each A/D and each upgraded ZOC pressure scanner has an inbuilt ID chip.

When a ZOC pressure scanner is connected to a RAD, it outputs the model, pressure range, number of channels, last calibration date and serial number.

The ZOC (zero, operate and calibrate) pressure scanners contain piezoresistive pressure channels in arrays of 16, 32, 64 or 128.

An RTD (resistance temperature detector) is installed within the ZOC to sense the scanner's temperature.

The data from the analogue pressure sensor and the RTD data are then digitised within the RAD and passed onto the PC for temperature corrected engineering unit conversion.

Also optionally fitted into the ZOC is a pneumatic calibration valve that allows for sensor rezero or multipoint calibrations on demand and this calibration valve also allows purging of the pressure input lines of condensation and contaminants.

Upon start-up the RAD software immediately interrogates the ZOC ID chip and auto selects the appropriate ZOC calibration coefficients for each ZOC module connected on the system.

To compliment its range of pressure scanners Scanivalve also manufactures an extensive array of miniature pressure fittings and clear plastic tubing in various materials.

Totalling almost 3000 standard parts and a made to order capability these accessories enable a complete system to be integrated with minimal effort.

The compact size of the pneumatic fittings along with the variety of stainless steel tubulations and connectors ensure that space requirements are kept to a minimum whilst maintaining packing density.

Tubing is available in a range of materials including Nylon, Teflon, Vinyl and Urethane and the tube connections themselves are available in a range of colours to aid in the identification of measurement lines.

Scanivalve also offers a range of quick disconnects, which provide the highest channel density per connector of all round connectors that are suitable for use at model or bulk head test points.

These pneumatic connectors are available in a number of configurations, providing various bulged tubulation sizes.

Single and double pneumatic manifolds are also available.

Various tubulation sizes and anodised aluminium colours compliment the range with up to 12 tubes available on the single manifold and 24 on the double.

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