Structural health monitoring.

New from Leine Linde and available with full support from Mclennan, the ESR strain sensor is measurement concept that offers a novel alternative to conventional strain gauges through improved accuracy, signal quality and especially durability. Particularly suited to large-scale machine structural health tasks where load or force needs to be reliably monitored, the ESR utilises Leine Linde’s robust optical encoder technology coupled to a mechanical measuring arm arrangement which is fixed to the structure’s strain-prone components.

With its integral EnDAT bi-directional digital interface, the ESR’s high resolution output of 0.025 μɛ (μm/m) can be connected to almost all available machine control systems and additionally can offer stored application-specific data that may be used for machine functions, for instance for safety or other operational tasks. Application areas for the ESR can include but are not restricted to structural monitoring on bridges, cranes and towers, wind turbine blades, large machine frames, construction equipment, bulk material conveying lines and more.

The strain sensor arm design features passive temperature compensation, and its stress-free measurement principle offers a practically unlimited operation life. Operational temperature can be designed for -40°C to +100°C and the measurement range covers ± 5 000 µɛ with a working range of ± 17 500 µɛ. The unit will fit into a volume envelope of approximately 340 x 80 x 85 mm (L x W x H). The ESR also boasts an impressive shock and vibration rating to ISO 60068-2-26, and its IP66 environmental rating offers trouble-free use in harsh environmental conditions.

For use as a temporary strain measurement tool or for permanent installation, the ESR’s measuring arm design and mechanical interface can be custom-adapted to the application with variant options and accessories available for adhesive, screw, or magnet installation. Other options include various measurement reports, quality control certifications or DAkkS calibration.

 #Mclennan #BAS @LeineLinde @mepaxIntPR

Measuring stress under pressure!

When Terex Pegson® MPS needed a reliable and flexible system to measure stress on its LJ5139 stone crushing machine, it turned to HBM to provide a comprehensive and effective solution.

Following a thorough study of the issues faced by Terex Pegson® MPS, HBM specified its rugged DAQ, SomatXR series, which is particularly suitable for use in harsh environments. To compliment this package, HBM also suggested the Somat MX1615B-R module and related accessories, which included RF-9 strain gauge rosettes.

Given the demanding environment, it was important that Terex Pegson® MPS specified the correct equipment. “Often faced with wet and arduous conditions, the ability to operate reliably under harsh conditions and sudden impacts was a key consideration for the customer when it came to suggesting the SomatXR system” explains Gregg Todd, HBM Mobile Data Acquisition Specialist.

The powerful SomatXR data acquisition system is specifically developed for use in harsh environments. The modules provide a wide temperature range and are protected from humidity, dust, shock and vibration.

The data acquisition system provides a web interface for simple operation without any software installation. This allows for convenient channel parameterisation, monitoring of measurement jobs and visualisation of measured data far away from the measuring point. This was a particularly significant feature for Terex® MPS, given the nature of the measurement task.

Another factor which was taken into consideration when specifying the Somat XR series was the operating conditions. For instance, when operating under such extreme conditions, it’s often hard to anticipate all of the problems that may occur, such as losing measurement data due to unforeseen events, such as a power failure. The SomatXR system enables data to be continuously recorded. This means that should a failure interrupt a test, recorded data up until that point will be saved. This was a particularly relevant feature in terms of the long term tests, typically performed by Terex® MPS.

HBM data acquisition systems are suitable for a wide range of mobile testing applications. Despite the immense load requirements and extreme environmental conditions, HBM was able to provide Terex® MPS with a reliable and flexible solution.

In addition to specifying and supplying Terex® MPS with a system to meet its needs, HBM also provided engineers with valuable training and continued support, where needed.

@HBMmeasurement #PAuto #Mining

Miniature Sensors for force, displacement, pressure, strain and acceleration.

The Micro-Measurements® brand of Vishay Precision Group, industry experts in the design, development, and manufacture of resistive-foil sensors for high-precision strain measurements, has introduced a new range of miniature, lightweight hybrid sensors, offering cost-effective force, displacement, pressure, strain and acceleration measurements within high-volume OEM and test applications.

Design of the new Micro-Measurements hybrid sensor range incorporates the brand’s own renowned precision foil strain gages, adhesively bonded to flat substrates, constructed of either metal, composite, or polymer. Hybrid sensors are manufactured by VPG using the same high-volume production equipment as those used to create its precision strain gages. The result is a cost-effective family of strain-gage based hybrid sensors with consistent batch-to-batch performance characteristics. Customers may further incorporate an optional miniature signal amplifier, as either a stand-alone component or attached to the sensor. Hybrid sensors may be attached via mounting holes with choice of screws, spot welding, or clamping, thereby eliminating adhesive bonding requirements. The hybrid sensors are further optionally available with pre-attached lead wires and connectors, for simplified customer handling without soldering requirements.

New hybrid sensors can effectively support a variety of high-volume OEM consumer product, process control, automotive testing, non-critical medical device, educational research, and industrial requirements. Typical consumer product applications include appliances, sporting equipment, hand tools, and lawn and garden equipment. Process control applications include HVAC, liquid-level sensing, motor control, and vibration monitoring. Automotive testing applications include passenger weighing, foot-pedal pressure, seatbelt tension, emergency braking, suspension control, and engine monitoring. Medical applications include pumps, respirators, and other non-critical devices. Industrial applications include elevators, tank monitoring, bearing insertion, safety systems, gas and liquid cylinder pressures, and load monitoring.

@Strain_Gage @VishayIndust #PAuto 

Strain sensors in monitoring of welding of “difficult” materials!

World leading manufacturer of resistance welding technology, Sciaky Electric Welding Machines Ltd, is using Kistler piezoelectric strain sensors to meet the demands of the aerospace industry for the precise monitoring of the welding process. The Kistler strain sensors are easier to fit, simpler to replace, more reliable and longer lasting than the load cells previously used.

With experience spread over 80 years and an impressive worldwide customer list, which includes most of the leading automobile and aerospace companies, Slough-based Sciaky has led the way in the development of resistance welding, especially of “difficult” materials. In particular, aerospace applications, where very clean aluminium and titanium are welded, demand reliable monitoring of the welding process. A critical parameter is the force exerted by the welding electrodes, which was previously measured by a load cell installed inside the ram connecting the weld cylinder to the electrode control mechanism. This required special machining and significant dismantling when replacement was needed. By contrast, the Kistler piezoelectric strain sensor, mounted externally on the main structure of the machine, requires only simple machining to provide a flat seating and a single tapped hole for mounting the sensor.

Unlike the load cell, the piezoelectric strain sensor measures the force at the electrodes indirectly by reference to the strain on the main body of the machine. The conversion from strain to force is achieved using a Kistler Type 5073A single channel industrial charge amplifier which is mounted on the machine remotely from the sensor.

In addition to fitting the sensors to new welding machines, Sciaky now retrofit the Kistler strain sensor whenever the old-style load cell needs replacing. According to Sciaky Managing Director, Louis Kunzig, the strain sensor is now fitted as standard to all Sciaky Resistance welding machines supplied for aerospace applications and for critical applications, such as manufacturing steering components, in the automobile industry.

Testing total vehicle durability!

Ford Europe commits many man hours to acquiring data from prototype test vehicles at its test track at Lommel in Belgium and, during the past 13 years, much of the Road Load Data (RLD) has been derived using Kistler RoaDyn Wheel Force Sensors over a wide variety of road surfaces. Ford has now upgraded its test capability with the purchase of ten of the latest Kistler RoaDyn measuring wheels and a set for use on test lab based vehicle simulators to ensure correlation between road and lab, a total investment of approximately €1M. The modular design of the Kistler RoaDyn Wheel Force Sensors enables Ford to test an extensive range of vehicles with wheel sizes from 15” to 19”.

According to Ford Europe’s RLD Supervisor, Mark Linn, the RoaDyn system is used on prototype vehicles being subject to total vehicle durability testing on a wide variety of road surfaces, from handling tracks to cobblestones and large potholes.

The data from the Wheel Force Sensors are used to predict the durability performance of vehicle chassis and body using CAE tools and also in the laboratory to provide load data to be applied to single suspension components and complete subassemblies, the objective being to combine minimum component weight with maximum durability to reduce total unsprung weight for best suspension performance.

Each RoaDyn wheel uses a number of three component strain gauge sensors to provide data that are used to precisely calculate the forces and moments acting on the rotating wheel. The high measuring accuracy of the precision load cells is retained during transmission as digitization takes place on the wheel to eliminate transmission interference from brake heat, movement, vibration, etc. The measurement of individual values with separate load cells also leads to an improvement in the interchannel crosstalk. As the original load cell signals are known, rapid error diagnostics is made possible. To maintain long life of the system, individual load cells can be replaced without impairing the overall quality of the sensor.

The RoaDyn Wheel Force Sensors can be constructed using either aluminium or carbon fibre reinforced (CFR) wheel rims, depending on the wheel size and vehicle loads.
During test, the measuring wheel replaces the standard wheel and must be as strong without affecting the kinematics or the handling of the vehicle. The Kistler Wheel Force Sensors using CFR are much closer to the weight of the standard wheel than measuring wheels made from aluminium or steel and have minimal effect on the kinematics or the handling of the test vehicle.

Over the past 13 years, Kistler Instruments has expanded its range of vehicle test solutions to include Corrivit™ optical speed and slip sensors, wheel vector systems and laser ride height sensors, offering the automobile industry a complete vehicle dynamics and durability solution.

"Central nervous system!"

A new smaller diameter optical sensing fibre of only 80µm, for intrinsic sensing within composite materials and textiles

The ability to embed sensors within a material gives engineers scope to measure intrinsic strain of components during their production, or use under varying load conditions. To build a sensor network within a component or structure like a human central nervous system, makes it possible to measure loads at almost any position or environment. This makes certain demands on the sensing fibre, not least of which is small size and in response to this FBGS has announced the launch of its smallest diameter DTG fiber at only 80µm.

The new fibre offers some exciting opportunities compared to standard 125µm DTG fibers.

Because the fiber is thinner:
1. it is less invasive when embedded within laminate composite structures or textiles;
2. it requires less force to strain it which makes it more suited for acoustic sensors and hydrophones and
3. because it is more ”elastic” in respect to its bending properties, it can be used in applications where small bend radii are required.

The fiber has been released as a Beta-product for the 1550nm window and is drawn with an Ormocer coating that brings the outer fiber diameter to about 114µm.

The new 80µm diameter fiber retains all the attributes of the larger 125 µm DTG product, including:
• extremely high mechanical strength
• spliceless FBG chains
• low bending loss (high NA fiber)
• wide temperature range (cryogenic to +200degC)
• Ormocer coating
• Uniform coating even at FBG position

CEO Hugo Mertens says “this development has come mainly as a result of market forces. The composite and textile industry is very exciting and manufacturers in this sector are starting to incorporate DTG’s for sensing applications. We are simply responding to requests for a fiber that is less invasive to the host material and at 80µm it is all but invisible”.

FBGS would like to build collaborations with those companies that share this vision for “smart materials”.

New website communicates strategic vision

Having recently announced a new strategic vision for the company, FBGS, supplier of innovative FBG’s for sensing of strain and temperature will communicate these changes to their customers and partners through a new website.

The brief given to the website developers was to reflect the highly innovative technology the company has become known for and secondly, to demonstrate to solution providers that draw tower grating technology (DTG™) offers advantages over traditional FBG’s.

According to European Marketing Manager David Johnson “Although the process is well established, the application of this technology is new to many of our customers in optical sensing. Because it offers a new approach to solving some very demanding problems, it is imperative that in the early stages especially they get the right support from the website.

Fortunately the process of firing a laser at a moving target of optical fibre offers good opportunity for graphic illustration and this has not been missed by our website developers. To demonstrate the benefits of DTG’s, the automated process of writing and then covering gratings has been achieved through the use of some very effective graphics.”

They mantain that they have effectively raised the performance bar in this technology and the new website will act as a central information portal for informing and supporting our customers. Also, potential new customers should be able to easily grasp the reasons why this technology is able to achieve all that we promise through this website.

Their draw tower process is cutting-edge and marks a step-change in optical sensing. A number of European manufacturers of traditional sensing systems have already committed to this technology and are employing it in their own range of sensing products.

CEO FBGS Hugo Mertens commented, “Whilst we have our own plans for product development, it is our customers that drive innovation as they are the ones asking us to provide more and more technically demanding solutions. With 30+ year’s collective experience of the industry, it is important that we bring this to bear through the new website and ultimately better support customers using our technology.”

Monitoring bridges in all weathers

RDP products are frequently used to measure movements in the structure of bridges caused by the weight of traffic, environmental conditions and other factors.

Higher traffic loads and corrosion can lead to increased strain in bridge components, such as suspension cable fixing points. It is important for engineers to understand movements and loads imposed on the structure in order to predict potential problems and to maximise the safe working life of the bridge. Ageing bridge structures may be reaching overload due to the effects of increased weights and traffic volumes on steel structures that may be also weakened by corrosion or suffering early metal fatigue.

Very often the transducers used to monitor movements are installed on structures in coastal regions where the rain water must be considered saline and transducers are also exposed to chemical pollutants created by road vehicles. RDP Electronics Ltd offers many different types of products with a very high water ingress protection rating. Transducers can be supplied that are moisture resistant or fully welded for submersible applications. Thanks to a stainless steel construction these transducers are suited to operation in marine environments and also resist the corrosive effects due to winter road treatments for ice.

The LVDT monitoring approach is relatively inexpensive particularly when several points on a bridge need to be monitored, calling for long cable runs. By using a 4-20mA 2 wire loop, the wiring installation cost can be considerably reduced, as well as this offering the best interface to use with long cables for temperature drift reasons.

The effect of girth tension on horse gait!

Ireland is famous for its livestock and the quality of its horses. This is an interesting application for the equine industry which is so important to both Ireland, Britain and throughout the world.

Using electrical systems for the measurement of mechanical forces is by no means limited to machines and laboratory based applications. In her recently completed research thesis ‘Girth Tensions and their Effects on Equine Stride Characteristics’, Sue Wright of Moulton College Northampton (GB) used load cells, motion sensors and GPS amongst other technologies to measure and record the tension within the girth strap used to hold the saddle in place.

The aim of the investigation was to determine if girth tension affects equine stride characteristics. The positioning and tightening of the girth strap has traditionally been based on the rider’s preference or own training, in the knowledge that too loose or too tight would be dangerous to both rider and horse.

It is well known that optimum girth tension varies between the size and type of horse, the activity –racing etc and the type of girth. However there is little if any published information on girth tension and how this may affect the locomotion of the horse, that is duration, stride length and speed.

A custom designed S-type tension load cell was used to continuously monitor the tension in the girth during the period under test. The load cell was mounted almost vertically alongside the chest of the horse where unwanted torsional effects on the load cell would be at their minimum, it was fitted to the strap via rod-end bearings and a cam buckle so that minute changes to the girth tension could be made.
This was connected to a T24 telemetry module, located in a pouch on top of the saddle which transmitted the force reading wirelessly to a telemetry base station located nearby. This was plugged into a laptop that served to both power it and log the tension reading.

Extensive testing on 19 horses at 4 girth tension settings were conducted resulting in definite conclusions on the effect of girth tension on the speed, stride length, stride duration and walk.

This application is typical of the way in which Applied Measurements’ custom force sensors are helping all sectors of research and development as well as solving the needs of industrial production.

Integrated signal conditioning for scalable, high-performance measurements

Strain, thermocouple and high-voltage analogue input modules offer increased accuracy for high-channel-count measurement systemsNational Instruments has announced the company’s first data acquisition (DAQ) modules with integrated signal conditioning for scalable, high-performance measurements on PXI Express. The new NI SC Express family delivers increased accuracy, high data throughput and best-in-class synchronisation for measuring strain gauges, bridge-based transducers, thermocouples and high-voltage analogue inputs. PXI Express provides 250 MB/s of dedicated bandwidth for each SC Express module in the chassis, which helps engineers increase channel count without compromising sampling rates or data throughput. With a smaller footprint, simplified cable management and new software features for automatic synchronisation, the SC Express modules make it easy for engineers to set up and program high-channel-count sensor measurement systems.

The PXIe-4330 24-bit simultaneous bridge input module offers 0.02 percent accuracy and 25 kS/s per channel sample rate for high-performance strain, load, force and torque measurements. The bridge input module achieves high accuracy with a ratiometric design where the ADC references the excitation voltage. This approach removes the measurement’s dependence on the stability and accuracy of the excitation voltage. In addition, unique delta-sigma ADCs provide both excellent AC performance as well as DC accuracy, while traditional delta-sigma ADCs only offer AC performance.

This bridge input module can perform quarter, half and full bridge-based measurements with automatic synchronisation features. The included driver software ensures tight synchronisation across multiple modules and chassis with inter-channel skews as low as 5 ppb. The 8-channel bridge input module can scale to a 136-channel system in a single chassis and thousands of channels when synchronising across multiple chassis. The high-accuracy, simultaneity and synchronisation features make the NI PXIe-4330 module ideal for high-channel-count structural test applications, such as wind tunnels, bridge monitoring and crash tests.

With the thermocouple module, engineers can measure temperatures with 0.30 °C accuracy on 32 channels. The isothermal terminal block minimises error with a unique design that optimises thermal conductivity, making it possible for the nearby cold-junction compensation (CJC) thermistors to accurately measure at the thermocouple junctions. The 32-channel thermocouple module can scale to a 544-channel system in a single chassis and thousands of channels when synchronising across multiple chassis. The increased accuracy and scalable platform make the NI PXIe-4353 module well-suited for precision measurements from a single channel to large systems for applications such as fuel cell testing and monitoring thermal chambers.

The high-voltage isolated analogue input module is the first analogue input module from National Instruments that can measure up to 300 V with simultaneous sampling. With a 16-bit ADC per channel and a 250 kS/s per channel sampling rate, the NI PXIe-4300 module can stream 4 MB/s per module and 68 MB/s in a single chassis. This 8-channel analogue input module can scale to a 136-channel system in a single chassis and thousands of channels when synchronising across multiple chassis. The ability to measure 300 V with CAT II channel-to-channel isolation makes the NI PXIe-4300 module ideal for automotive testing, such as fuel cell and battery tests.

The new SC Express modules include NI-DAQmx driver software and support for multi-device tasks, a new feature of NI-DAQmx that helps engineers easily synchronise multiple modules. The same code that acquires data from one module can synchronise up to 17 modules in a chassis. The modules work with a variety of NI hardware including NI X Series, dynamic signal acquisition (DSA) and NI SCXI products, and more than 1,500 types of I/O available on the PXI platform. The new modules also integrate with NI software including NI LabVIEW and the LabVIEW Real-Time Module, NI-Sync and NI DIAdem.

Young Stress Analyst competition

The BSSM’s (British Society for Strain Measurement) annual Young Stress Analyst Competition, is scheduled to take place alongside the 7th BSSM International Conference on Advances in Experimental Mechanics, to be held in Liverpool (GB) from the 7-9 September 2010.

The competition is sponsored by Airbus, AWE and Imetrum Non-Contact Precision Measurement and will give four finalists the opportunity to present their work at a special session at the Conference.

The first prize winner will receive Imetrum Non-Contact Precision Strain Measurement software and a cash prize of £200; cash prizes will also be awarded to the other three finalists. All four finalists will receive free conference registration, a contribution towards B&B accommodation, lunches and refreshments over the three days of the conference and will be invited to attend the conference dinner free of charge on Wednesday 8 September to receive their prizes. Other entries of merit will be invited to produce a poster for display at the conference, which will also be entered into a competition.

The competition is open to final year undergraduate (or equivalent) students, MSc students, PhD students who have not submitted their final thesis and industry based personnel. The closing date for receipt of entries is 29 June 2010. Full details about the competition and an application form can be found online.

Last year’s competition was a great success by all reports and they would like this year’s event to be even better. This is a great way of getting young, enthusiastic people interested in experimental mechanics and the BSSM.