Sensor Technology Ltd

  1. Talking the torque at Hannover
    21 March 2017

    The company will be showing its full range of products and capabilities on its stand (Hall 11, Stand Number F33). Sales Manager Mark Ingham, who will be manning the stand, says:

    “Hannover is always good for us, as each year it seems to help us expand our international profile just a little bit more. Last year we found several new customers, but perhaps more importantly we also found a couple of new overseas distributors. In this case, they were both in Central America and we have seen a notable and sustained growth in a region where we had not been so active previously.”

    He explains that because TorqSense is often used on development and testing work, the networking opportunities at the Messe are very important.  Sometimes a conversation at Hanover leads to business a year or more later.

    “People with actual torque sensing requirements will make a point of coming to our stand, but we also get quite a lot of people who are passing and stop because they see something that they may need in six or eight months time.”

    LoadSense is a slightly different proposition. Its basic concept of wireless operation is still fairly new in the market and a lot of people have not yet realised that it may offer a solution to a particular issue they are addressing.

    Mark again: “Sometimes it’s a bit of a ‘eureka’ moment for a stand visitor. They suddenly see a simple solution to something that has been at the back of their mind for a while.”



    LoadSense was originally developed to show helicopter pilots the weight on their cargo hook. The wireless operation meant there was no need to drill through the fuselage for a signal cable, which would have compromised the craft’s Certificate of Airworthiness. Today its wireless ease of installation also makes it a favourite for many land based applications.

    Sensor Technology already has strong European distribution arrangements in place, and says it is the global reach of Hannover that is particularly useful.

    “We hope to build on last year’s success by finding distributors for South America now, as well as Poland, Hungary and Romania” says Mark. “While TorqSense and the strain gauge products are well established, we are still introducing LoadSense to many regions. A few days in Hannover are usually worth several months of flying around the world to see individual people.”

    Talking the torque at Hannover
  2. Reliable torque sensing at low speed or low capacity
    27 February 2017

    Those figures on the datasheet won’t necessarily guide you towards the right product for your application, but they’ll give you an indication of where to start a conversation with a supplier.

    However, while figures on maximum speed and maximum capacity can give you an indication of performance at one end of the dynamics scale, they tell you next to nothing about performance at the opposite extreme.

    At low speed or low torque values, the mechanical design of the rotary torque sensor has a much greater impact on factors such as accuracy, resolution, hysteresis and linearity, and environmental factors such as temperature really come into play.

    Consider, for example, the strain gauge torque transducer employing slip rings to make the electrical connections from the casing to the rotating shaft. The strain gauge itself is bonded directly to the shaft, and connection is made via brush contacts.

    In many applications, this will provide a useful and reliable solution, particularly as the principle disadvantages of the system are well known and generally reported within the product datasheets. In particular, while at low speed the electrical connection between the rings and the brushes are relatively noise-free, at increasing speeds electrical noise gradually has a greater impact on the output, eventually dominating and so decreasing the reliability of the output signal.

    This maximum speed criterion for slip ring systems is a well known limitation, making them generally unsuitable for use in highly dynamic applications.

    What is less well understood, however, is the suitability of slip ring based systems for very low torque applications. While the datasheet might hint at a torque capacity from zero to some upper torque limit, for very low capacity measurements the friction of the brushes themselves on the slip ring comes into play, and is an important limiting factor on the reliability of the output and the accuracy of the system.

    Suppose instead that strain gauge is connected via a rotary torque transformer. As a non-contact implementation, this overcomes the wear of the brushes in applications towards the higher end of the speed limit, even if it doesn’t particularly extend that maximum speed, due to the need for bearings and the fragility of the transformer cores. At the higher end of the speed range, it is also recognised that noise and errors included by the alignment of the coils come into play.

    What is less often discussed, however, is the potential for difficulties at the opposite end of the performance curve, in low speed applications. The physics of the construction and the limitations of the required signal conditioning technology can quickly impact on resolution at the very lowest speeds of operation, potentially making the device inherently unsuitable in a given application. Further, while linearity errors can be ignored at or near full capacity, they are an important limitation for low capacity torque measurement.

    A torque measurement technique that has found favour in highly dynamic applications – with Formula 1 being a prime example – is the magneto-elastic torque sensor, built on the principle that the magnetic field of a material changes as it twists. Within its defined operational range, the resulting changes in magnetic field are proportional to the applied torque and can be measured by magnetic field sensors enabling the torque value to be derived.

    However, at low speeds the change in magnetic field is decidedly non-linear, limiting the usefulness of the technology in such applications. Further, at low speeds, the impacts of environmental factors such as temperature are much more pronounced.

    One technology that does lend itself to low rotational speed or low capacity applications is the surface acoustic wave transducer. This is a relatively new technology that measures the resonant frequency change of surface acoustic wave (SAW) devices in a non-contact manner when strain is applied to a shaft to which SAWs are fixed. The applied torque causes a deformation of the quartz substrate of the SAW device, which in turn causes a change in its resonant frequency.

    Practical torque sensors such as those produced by Sensor Technology use two tiny SAWs made of ceramic piezoelectric material containing frequency resonating combs. These are glued onto the drive shaft at 90 degrees to one another. As the torque increases the combs expand or contract proportionally to the torque being applied. In effect the combs act similarly to strain gauges but measure changes in resonant frequency.

    The adjacent RF pickup emits radio waves towards the SAWs, which are then reflected back. The change in frequency of the reflected waves identifies the current torque. This arrangement means there is no need to supply power to the SAWs, so the sensor is non-contact and wireless.

    Easily embedded within a system design, and with complete freedom from brushes or complex electronics, the SAW based rotary torque sensor eliminates the problems of alternative solutions not only in the most dynamic applications, but also in the lowest speed and lowest capacity tasks. Not only is its output inherently linear and stable at low speed or low torque, but it is also completely immune to environmental factors such as temperature, magnetic field, vibration and electrical noise.

    Low speed or low capacity tasks form an important subset of applications for torque sensors. For example, a radio telescope may rotate at speeds as low as one revolution per day, and the large scale solar panel arrays that track the sun rotate at similarly low speeds.The mixing of many non-Newtonian liquids is not only carried out at low speed, but requires speed to vary reliably as torque changes to ensure consistent quality. Sensor Technology SAW-based rotary torque measurement sensors excel in these low speed or low torque capacity applications. As well as offering performance that extends to the highest levels of required torque and speed, they can also be reliably used at rotational speeds from 0Hz upwards, and from zero torque to just a few mNm. As such, surface wave acoustic torque measurement technology is opening up potential in a whole host of demanding low speed and low torque applications, delivering new levels of accuracy and stability.

    Reliable torque sensing at low speed or low capacity
  3. Optical rotary torque sensors suitable for low torque and high band width measurements
    11 January 2017

    The new ORT 230/240 devices replace Sensor Technology’s E200 ORT series, benefiting from all-new electronics that deliver significant gains in resolution, frequency response, reduced sensor current consumption and faster digital data throughput.

    The high speed capability comes from an inherently low inertia, since the electronics are not fixed to the shaft, while non-contact operation ensures a long and reliable life (backed up by Sensor Technology’s lifetime warranty) with high accuracy. The optical operating principle also ensures excellent noise immunity.

    TorqSense ORT 230 series sensors provide fixed voltage or current analogue outputs – one for torque and one for either speed or power. The TorqSense ORT 240 provides two user selectable voltage or current analogue outputs – one for torque and the other for either speed, power or peak torque – plus digital outputs including RS232, CANbus and USB for interfacing with modern instrumentation and laptops. The ORT 240 enables users to connect up to 10 transducers via USB, and transducer configuration software for making changes to transducer variables.

    Features of both devices include self-diagnostics to report if the transducer’s torque, speed ratings or calibration date have been exceeded, while inbuilt sensors monitor shaft temperature for better compensation and accuracy. The device also offers a simple ‘sensor status’ output.

    Complementing these products is Sensor Technology’s TorqView software, providing an easy-to-use advanced torque monitoring package for Windows PCs to assist with data display and recording. It offers real time chart plotting, and is compatible with both Matlab and Excel. Further, LabVIEW VIs are available for users to design their own process control applications, and DLLs are available for users who wish to write their own custom software.

    These latest optical rotary torque sensors are an important extension to the Sensor Technology torque monitoring range, and offer an alternative solution when low torque or bandwidth requirements preclude the use of the more cost-efficient SAW-based TorqSense products.

    Optical rotary torque sensors use a pair of gratings attached a short distance apart on a strain-sensitive shaft to modulate a light source. As torque is applied to the shaft, a slight twist results which changes the alignment of the gratings and thus varies the light transmitted through to a detector. The use of this technique results in a transducer which is able to detect torque bi-directionally, and which has a fast mechanical and electrical response, low inertia and complete freedom from brushes or complex electronics.

    The absence of brush gear allows high-speed operation with a continuous rating up to 30,000rpm standard. Further increases in rpm are available depending upon shaft size. The torque shaft is of low compliance ½° maximum torsion deflection on the smaller transducers and ¼° maximum on the larger transducers at full-scale deflection. Any full scale torque can be specified within the range 10mNm to 100Nm.

    Optical rotary torque sensors suitable for low torque and high band width measurements
  4. Improving asset availability to reduce coal handling costs
    19 November 2016

    Coal is an important global resource and likely to remain so for many years to come. It is a crucial element in the energy mix and vital in the manufacture of a great many other products. But now more than ever, the pressure is on to reduce transportation costs by improving the efficiency of coal handling operations.

    Coal represents a significant proportion of all dry bulk, and handling and transportation of this challenging material is a major consideration. It is particularly important to make sure that handling equipment is reliable in the long term because breakdowns can lead to considerable downtime, reductions in efficiency and unforeseen costs.

    Coal conveyors are heavy-duty electro-mechanical systems that start and stop under heavy load. Unsurprisingly, they are prone to ingress from harsh coal dust and related debris, and their working conditions can be far from ideal as well with dramatic swings in temperature plus driving rain, sleet and snow, ice build-up etc.

    In an industry where downtime due to mechanical failure is often viewed as an unavoidable fact of life, British company Sensor Technology of Banbury is developing technologies that can help operators to boost long-term reliability, increase availability, and reduce unscheduled maintenance. This can be vital for the coal handling sector as it looks to drive down costs, boost uptime and optimise efficiency.

    Sensor Technology’s offering to the coal handling and transportation industry is built around its non-contact digital torque monitoring technology. Applied to the control systems for conveyors, it can transform these processes into accurately monitored and optimally managed systems.

    Accurate monitoring of torque is a key indicator of impending mechanical problems. The data can also be used to ensure conveyors are being run at optimum speeds, and that mechanical shocks are being minimised. This is because torque data is directly related to the power from the drive shaft. As coal is added and the conveyor load increases, so more power is needed. Similarly, if the conveyor is run at a higher speed, more power is needed. Controlling conveyor speed accurately helps to minimise shock loads, and so leads to both increased reliability and increased efficiency.

    Traditionally torque data has been hard to collect, with wired technologies vulnerable to the challenging environmental conditions inherent in coal handling operations, while also being expensive and difficult to set up. Wireless technology presents an important alternative that is being recognised as a real enabler for monitoring torque in even the most demanding applications.

    With over 20 years of research and development into digital torque monitoring, Sensor Technology is at the forefront of this technology and is an acknowledged leader in the manufacture of wireless load sensors. It has a global network of distributors assisting sales, and a network of world-renowned technical experts assisting in the development of technology.

    The company’s TorqSense transducer is based on the patented technology of measuring the resonant frequency change of surface acoustic wave (SAW) devices. TorqSense torque sensors use two tiny SAW devices or SAWs made of ceramic piezoelectric material containing frequency resonating combs. These are glued onto the drive shaft at 90 degrees to one another. As the torque increases the combs expand or contract proportionally to the torque being applied. In effect the combs act similarly to strain gauges but measure changes in resonant frequency.

    The adjacent RF (radio frequency) device transmits radio waves towards the SAWs, which are then reflected back and picked up by the device. The change in frequency of the reflected waves identifies the current torque. This arrangement means there is no need to supply power to the SAWs, so the sensor is non-contact and wireless.

    This innovative method of measuring torque can bring distinct advantages to coal conveying, whether in extracting coal from the mine, or transporting it for processing, or as part of subsequent shipping operations. A process that was once regarded as very difficult to monitor can now reap the same benefits as many other industrial processes.

    TorqSense technology can also improve on the torque limiters that are traditionally relied on to prevent mechanical damage in the event of a coal conveyor jam. Continually monitoring the torque, the transducer can identify the gradual increases that are indicative of an impending jam condition, so enabling preventive maintenance. This key technology can deliver significantly reduced downtime that might have been caused by blockages or breakages to conveyor chain, paddle attachments or the drive gearbox.

    TorqSense has seen widespread adoption in torque monitoring applications across a host of industries, where it is recognised as providing a reliable, accurate and easy-to-implement monitoring solution. Increasingly, these applications are including conveyors, where operators are finding that accurate, non-contact, digital torque monitoring technology has an important role to play in optimising operations and reducing costs.

    Sensor Technology can point to a number of applications within coal handling and transportation as well, from the conveyors at the coal face to the bulk unloading conveyors at docksides. Operators around the world are seeing its benefits of reducing running costs and improving asset availability by facilitating proactive rather than reactive maintenance.

    Improving asset availability to reduce coal handling costs
  5. Sensor Technology pushes the envelope with key product developments
    19 August 2016

    New and developing technologies will be the theme on the stand of one the regular exhibitors at this year’s Sensors & Instrumentation, the exhibition for test, measurement and control engineers, 28-29 September 2016, NEC Birmingham.

    Sensor Technology Ltd will be showing extensions to its LoadSense range, an updated version of its ORT 230/240 range and enhancements to its wireless strain gauge amplifier.

    The new ORT sensors redefined user expectations for optical rotary torque transducers when they were introduced earlier this year. These torque sensors are designed for duties requiring low torque and/or high bandwidth, and provide precise, dynamic measurement of rotary and static torque from 10mNm to 100Nm and for bandwidths of up to 50 kHz. Their signal processing electronics demonstrate improved resolution, frequency response and faster data handling, yet have reduced power consumption.

    Complementing the ORT sensors, Sensor Technology is also introducing new strain gauge amplifiers, which are wireless so offer many benefits in terms of ease of installation, use and reconfiguration.

    LoadSense is a strain gauge based stainless steel tension type sensor with the capability of wirelessly transmitting its data (via 2.4 GHz) to a display. Alternatively, it can record data to its inbuilt 32MB memory for subsequent downloading and use/analysis. New this year, the range has been extended up to 30 tonnes.

    LoadSense is now found throughout the worlds of manufacturing, automation, handling and test and measurement, but it was originally developed to measure the load on helicopter cargo hooks and transmit information to the pilots wirelessly (a hard wired solution would have required a hole to be drilled in the aircraft’s body, negating its certificate of airworthiness).

    The company’s Tony Ingham says: “Much of our business is overseas, but the domestic market remains very important for us as the UK is a leader in so many high tech fields. Sensors & Instrumentation and its predecessor shows have always produced new leads and introductions for us; it’s an event we look forward to every year.”

    Sensor Technology pushes the envelope with key product developments
  6. Measuring viscosity wirelessly
    19 July 2016

    If precise mixing is a crucial process variable, viscosity measurement may be the most accurate way to ensure optimum performance. But rotating mixers can lead to very tangled wiring, so here Mark Ingham of Sensor Technology Ltd looks at wireless options.

    Mixing is fundamental to the manufacture of many products; in many cases this need not be a precision operation – although over-mixing is a waste of time and energy. However in other cases, mixing is more of an exact science; under-mixing will leave the various component materials unevenly distributed, while over-mixing may change the state of the end product.

    One example of this is mixing concrete. If you are building a DIY patio, you can splash some water into a pile of ready mix and working it in with a spade, but if you are building a containment bunker for nuclear waste or the foundations of a skyscraper, quality control shifts to a different paradigm! In the latter case the wet concrete has to be fluid enough to flow into every nook and cranny of the formwork and for no pockets of dry concrete that won’t cure properly.

    Another example is mixing ketchup, sauces, mayonnaise, etc. The food industry relies on the fact that consumers can be loyal to a particular brand their whole lives, but are also so fickle that the slightest variation in texture will have them up in arms.

    Similarly, drugs and medicines must have the active ingredients precision mixed with the carrier material - the consequence of poor mixing could be life threatening.

    And in cosmetics and toiletries, the users have incredibly high expectations. Even something as apparently mundane as paint requires that pigments are well mixed in for an even colour and that the correct consistency is attained for easy application.

    There are a number of different technologies available for measuring viscosity, but one of the most popular and widely used is the rotational viscometer, which measures viscosity by monitoring the torque required to rotate a spindle at a constant speed within the fluid. The torque, generally measured by determining the reaction torque on the motor, is proportional to the viscous drag on the spindle, and thus to the viscosity of the fluid.

    Significantly, the rotational viscometer can run throughout the mixing process, logging data constantly to provide a log of the change in viscosity over time. This profile can be compared with historic data from earlier mixes to give detailed information that would not be available from final target viscosity readings alone.

    However torque can be difficult to measure; in fact traditional measuring technologies introduce as many problems as they solve. Because the spindle is rotating, wires attached to a torque sensor on the shaft would wind up and quickly snap. Approaches using slip rings are available but far from ideal because of costs, set-up time and the inevitable wear and tear.

    A wireless technique has been developed using TorqSense rotary torque transducers from Sensor Technology. These do not need a physical connection to the rotating shaft, but instead use a radio frequency (RF) link to both send power to the sensing element on the spindle and to receive torque reading signals back from it.

    TorqSense torque sensors use two tiny Surface Acoustic Wave devices or SAWs, made of ceramic piezoelectric material containing frequency resonating combs. These are glued onto the drive shaft at 90 degrees to one another. As the torque increases one comb expands and the other contracts proportionally to the torque being experienced. In effect the combs act as strain gauges but measure changes in resonant frequency.

    An RF transmitter/receiver mounted close to the spindle emits radio waves towards the SAWs, and collects them when they are reflected back. The change in frequency of the reflected waves identifies the current torque.

    In the rotational viscometer, the TorqSense transducer is mounted between the motor and the paddle. A double bearing eliminates any side loads, while a torque limiting coupling provides protection in the event of the paddle mechanism seizing. With the motor operating at constant speed, the transducer provides an output of torque that changes proportionally to the viscosity during mixing, thus enabling the operator to accurately measure the relative viscosity of the mix.

    Where it is important to determine absolute viscosity rather than relative viscosity, the system can be pre-calibrated using specific paddles immersed in fluids with a known viscosity. Water, for example, has a viscosity of 0.001 Pascal seconds at room temperature. By calibrating the viscometer to a known sample, the absolute torque figure can then be derived in the application from the relative torque figure, and the required viscosity then accurately measured.

    Using TorqSense rotary torque transducers has simplified the design of these new rotational viscometers while also increasing accuracy, providing a robust and reliable solution in challenging applications where the absolute viscosity of the mix is a critical factor.

    Measuring viscosity wirelessly

Buy from Sensor Technology Ltd

Request a Quote
Can we help?