Draw-wire sensors used for wind turbine rotor blade testing

Draw-wire displacement sensors from Micro-Epsilon are playing a vital role in the testing of the latest generation of wind turbine blades at the Fraunhofer Institute in Bremerhaven, Germany.

The test rig at the Fraunhofer Institute simulates the distortion of rotor blades due to the effects of wind forces. The tip of the rotor blade can be distorted by up to 10m due to mechanical loads. The rig is designed to measure rotor blades up to a length of 70m.

During tests, the rotor blade itself is mounted horizontally in the test rig. Steel cables are attached to the rotor using guide pulleys and fixed to the rotor blade at various positions along its length, either directly or via mechanical clamps. Twelve draw-wire sensors from Micro-Epsilon are used to measure the distortion. (Refer to picture on the right).

Two draw-wire sensors for each cable are mounted to the rails on the floor. These sensors measure the movement and the distortion of the rotor blade. The P115 sensors are from Micro-Epsilon's wireSENSOR range and have measuring ranges of between 3m and 10m. The sensors operate with a digital output signal and are particularly robust due to their aluminium housing.

The principle of a draw-wire displacement sensor is relatively straightforward, hence its inherent reliability. A draw-wire sensor works rather like a tape measure, except the user does not have to read off the measurement of the extended tape. The rotation of the drum on which the steel wire is wound is measured automatically. The drum itself incorporates a long-life spring drive, which ensures the steel wire is rewound.

Chris Jones, Managing Director at Micro-Epsilon (UK) Ltd comments: "In addition to wind turbine testing, our draw-wire sensors are being used in a wide range of applications, from general industrial machinery and scissor lifts, through to more specific uses such as dentist chairs, patient lifting tables, theatre stages, pneumatic and hydraulic systems, aircraft landing gear and forklift trucks. Our wireSENSOR range is proving very popular with UK machine builders and OEMs, who require low cost, robust, reliable sensing solutions that can be easily integrated into their customer's existing machine, components or control and automation systems."

The wireSENSOR range uses three main measurement methods: a multi-turn potentiometer, an incremental encoder or an absolute encoder. One of these devices is mounted onto the drum axle, converting the rotary motion of the drum into a signal that can be evaluated. The measured displacement can be output as an analogue current, voltage or potentiometric signal. For a digital output, there is a choice of HTL or TTL, with interfaces for most of the common fieldbus systems, including CANopen, SSI and Profibus.

As with traditional tape measures, the wireSENSOR series is capable of measuring around corners and edges. Micro-Epsilon supplies as accessories deflection pulleys, which deflect the steel wire in the desired direction.

For further information, email: info@micro-epsilon.co.uk or view website: www.micro-epsilon.co.uk    Refer to page 76

ADLINK Technology expands high-resolution digitizer product line

ADLINK Technology Inc.(TAIEX:6166), a leading global provider of test and measurement products, announced the release of an expansion to their digitizer product line with the introduction of three new PCI digitizers, the PCI-98x6 series. The PCI-9816, PCI-9826 and PCI-9846 4-channel, 16-bit high-resolution digitizers offer sampling rates of 10 MS/s, 20 MS/s, and 40 MS/s respectively, complete the ADLINK 98x6 family of digitizers, following the introduction of the their PXI-based PXI-98x6 digitizers in February.

The PCI-98x6 series combines three characteristics that make them optimised for various applications - high 16-bit accuracy, low noise, and high dynamic performance over wide range of frequency domain, making them ideal for applications such as radar/lidar design and test, ultrasonic imaging, non-destructive testing, spectral monitor, and automatic electronic testing.. For example, the typical dynamic performance for the PCI-9816 includes 12.6-bit effective number of bits (ENOBs) and a 78.4 dBc signal-to-noise ratio (SNR) at an input frequency of a 1 MHz sine wave.

For applications that need high-density channels in one system, the PCI-98x6 series provide a specially design system synchronization interface (SSI) to synchronize up to 4 cards. Each member of the PCI-98x6 series also includes up to 512 Mbytes of onboard memory for ample data storage to allow extended the acquisition times. 

"High dynamic range is one of the most import features for a digitizer, especially in IF signal acquisition applications," stated Catherine Wu, Senior Product Director at ADLINK. "With the PCI-98x6 series of high resolution digitizers, customers will be able to measure very low-level signals in the presence of large signals, and thus increase the resolution and accuracy of the analysis of the results."

ADLINK provides both legacy drivers for program development in Microsoft C++ and Visual Basic and task-oriented drivers, such as DAQPilot, to accelerate the development cycle. The PCI-98x6 series of digitizers can be configured and operated in NI® LabVIEW® by using DAQPilot's Express VIs and Polymorphic VI.

ADLINK Technology in profile
ADLINK Technology provides a wide range of embedded computing products and services to the test & measurement, automation & process control, gaming, communications, medical, network security, and transportation industries. ADLINK products include PCI Express®-based data acquisition and I/O; vision and motion control; and AdvancedTCA, CompactPCI, and Computer-on-Modules (COMs) for industrial computing. With the acquisition of Ampro Computers, Inc., ADLINK also provides a wide range of Extreme Rugged and Rugged Single Board Computers, Computer-on-Modules and Systems under the brand name Ampro by ADLINK. ADLINK strives to minimize the total cost of ownership (TCO) of its customers by providing customisation and system integration services, maintaining low manufacturing costs, and extending the lifecycle of its products. ADLINK is a global company with headquarters and manufacturing in Taiwan; R&D and integration in Taiwan, China, and the US; and an extensive network of worldwide sales and support offices.

ADLINK is ISO-9001, ISO-14001, and TL9000 certified, is an Associate Member of the Intel® Embedded and Communications Alliance, an Executive Member of PICMG, and a Sponsor Member of the PXI Systems Alliance. ADLINK is a publicly traded company listed on the TAIEX Taiwan Stock Exchange (stock code: 6166).

All other products and company names appearing herein are trademarks or trade names of their respective companies. LabVIEW is a trademark of National Instruments Corporation. Windows is a registered trademark of Microsoft Corporation.

ADLINK also offers customized input ranges or higher bandwidth options on the PCI-98x6 series for OEM applications.

For further  information, view website: http://www.adlinktech.com

SDI-12 submersible level transmitter offers high accuracy and stability

A new range of submersible hydrostatic level transmitters has been launched, which can be used in depths of up to 200 metres. The transmitter offers an SDI-12 digital output and an inbuilt high accuracy temperature sensor.

The SDI-12L range of submersible level transmitters from Impress Sensors & Systems Ltd uses either a stainless steel silicon-based pressure sensor or a ceramic pressure sensor in marine-bronze. Both versions use piezoresistive technology, which provides long term stability and repeatability of measurements.

The transmitter is ideal for a wide range of applications, including the monitoring of river and reservoir levels; tanks and vessels in process plants; seawater and estuary levels; borehole water levels; Tsunami and tidal monitoring systems; wave height measurement; environmental monitoring; and V-notch weir flow measurement.

The stainless steel version offers a higher resolution of pressure measurement to around 12-13 Bit and has a much lower signal-to-noise ratio, providing a very smooth and accurate method of level measurement.

The ceramic pressure sensor version is better suited to marine use, where standard devices may suffer from corrosion. These units are ideal for seawater, estuary and saline applications.

The SDI-12L offers measurement ranges from 0.5mWG up to 200mWG. The output units can easily be adjusted to mmWG, cmWG, inHg and all the standard engineering units required via the SDI-12 interface and command structure. Temperature range of the transmitter is from -20 deg C up to +60 deg C. Accuracy of the inbuilt temperature sensor is less than ±0.1% of full-scale output.

Due to its SDI-12 compatibility, the transmitter can be corrected according to the specific density of the media being measured and local gravity can be set within the device, adding further to the accuracy of the unit.

What is SDI-12?
SDI-12 stands for serial data interface at 1200 baud. This standard was developed in order to interface battery-powered data recorders to micro-processor-based sensors designed for environmental data acquisition (EDA).

EDA is accomplished by using a sensor(s) and a data recorder that collects and saves the data. SDI-12 is a standard communications protocol that provides a method of transferring measurements taken by a smart sensor to a data recorder. The sensor typically takes a measurement, makes calculations based on the raw sensor reading, then outputs the measured data in engineering units.

SDI-12 is particularly useful in applications where battery-powered operation with minimal current drain is required, or where the use of one data recorder with multiple sensors on a single cable is necessary. This includes acquiring hydrologic data at remote sites, which use battery-powered data recorders that operate for long, unattended periods of time.

The SDI-12L is ideal for borehole pump applications. Here, submersible pumps are used to pump water from bottom of the hole to the surface. For the pumps to operate efficiently, they must maintain a level of water above them to prevent them running dry, which can destroy a pump in a short period of time.

The SDI-12L can either be submersed with the borehole pump and attached to the bracketry or retrofitted by lowering the device into the borehole to a known height from the cable distance. The sensor will then output a signal to the surface via the cable, which can then be converted to a level reading. Using a digital process display, this signal can then be used to trigger a relay and turn the pump off if the water level is too low or switch the pump on if the level in the borehole has risen too high. For further information, e-mail: info@impress-sensors.co.uk    Refer to page 110