Current affairs: the latest in current sensing

Current sensing is now more accurate than ever following the launch of a new measurement transducer.

Measurement specialist LEM has claimed record levels of accuracy and performance in current sensing with the launch of its IN 200 current measurement transducer.

As the most accurate sensor of its kind on the market, the IN 200 is ideal for use in such demanding applications as high-precision test & measurement (T&M) equipment used to analyse the efficiency of inverters fitted to hybrid electric vehicles (HEVs) and electric vehicles (EVs).The IN 200 is able to offer significant performance improvements – particularly in terms of linearity, offset and noise immunity – over traditional fluxgate transducers through its use of a new kind of digital technology.

Unparalleled levels of accuracy are achieved in linearity and electrical offset. While the IN 200’s data sheet quotes 0.6 parts per million (ppm) and maximum 10ppm respectively, in-house tests have shown that the sensor can achieve linearity below 0.5ppm and offset of +/-5ppm.This compares with competitors’ transducers offering +/-20-25ppm.

A leading company in electrical measurement, LEM engineers the best solutions for energy and mobility, ensuring that its customers’ systems are optimized, reliable and safe. With 1,500 people in over 15 countries transforming technology potential into powerful answers, LEM develops and recruits the best global talent, working at the forefront of mega trends such as renewable energy, mobility, automation and digitisation.

With the new transducer fitted to automotive test benches, manufacturers will be able to improve the testing efficiency of inverters and validate their performance levels through access to the most accurate data. In turn, because inverters will reduce power losses, designers will have the potential to tackle the issue of “range anxiety” by enabling EVs to go further than is currently possible.

The IN 200 completes LEM’s IN family of High Precision sensors which now covers a current range from 100A to 2000A. The IN 200 itself is effectively three products capable of matching nominal currents of 100A, 200A and 400A.

The single biggest factor that sets the IN 200 apart from the competition is LEM’s switch from reliance on analogue circuitry to digital integration technology. To achieve the increasingly high levels of accuracy demanded by the T&M market, LEM is reinventing fluxgate technology. Traditionally, many analogue circuits would be required to cancel out noise and other impacts of having different fluxgate coils but LEM’s innovative solution makes it possible to reduce substantially the number of analogue circuits within the transducer through digital integration, transforming the signal. By operating in the digital domain, the new sensor offers a wider range of capabilities – including ripple compensation, detecting second harmonics and voltage regulator excitation.

LEM believes that the IN 200 is a long way ahead of its nearest competitor in virtually every single parameter. While the market has shown that it can manage with the lower performance levels offered by other power measurement transducers, the IN 200 offers manufacturers the potential to take accuracy and efficiency figures to hitherto unachievable highs.

“The trend is very clear,” says Horst Bezold, founder of Signaltec. “The increasing electrification of transport is putting huge pressures on test benches for inverters in the automotive sector and has generated a boom in demand for T&M equipment. LEM has come up with a market-leading solution that will help to ease these pressures. By eliminating traditional reliance on analogue technology, we have made it possible to reach levels of accuracy that nobody in the market has ever been able to reach. This is great news for the T&M sector.”

The IN 200 offers users many additional benefits, including significant noise reduction and outstanding immunity to external fields. The device’s digital technology ensures immunity to temperature effects, interference and supply voltage variation while its top-quality metallic housing (previous models used a plastic casing) improves EMC immunity, reduces temperature drift and enables high-precision operation over an extended temperature range (-40°C to +85°C).

Other features of the IN 200 include very broad frequency bandwidth – DC to 1.1 MHz (-3 dB) – compact design with a 28mm aperture for cables and busbars, and a status signal to indicate transducer state.




Melexis gives robots a sense of touch

Melexis has made a major innovation to improve robots’ ability to interact with fragile or diverse objects. The company has unveiled Tactaxis, a fully integrated tactile sensor that is compact, soft and provides the 3D force vector acting on its surface. This improves robots’ hands and grippers, making delicate operations such as fruit picking possible. The technology is successfully implemented in a functioning prototype.

The ground-breaking prototype features multiple 3D magnetometer pixels, using Melexis’ industry-proven Triaxis® technology. The sensor is accompanied by a magnet which is embedded into an elastomer material. This presents a soft contact interface, emulating the attributes of human skin. The arrangement offers a high sensitivity so that detection of even small amounts of force will generate a response. The achieved force resolution is 2.7 mN which is enough to distinguish weight change of a fraction of a gram (~ 0.3 gram). The Tactaxis prototype is highly compact (with dimensions of just 5 mm x 5 mm x 5 mm) and therefore suitable for tight spaces.

The gradiometric approach makes the sensor immune to magnetic stray fields. This prevents potential measurement errors. It is also robust enough to cope with harsh conditions (temperature variations, etc.). Unlike competing optically-based tactile sensors, Tactaxis is completely integrated. It will be possible to produce high volumes of factory-calibrated sensors. This semiconductor process results in major cost and reliability benefits.

“Robots need the sense of touch to manipulate fragile objects. For such applications, we have developed a novel magnetic sensor to accurately measure the contact force—while being robust against disturbances,” explains Gael Close, Global Innovation Manager at Melexis. “By exploiting the capabilities of our Triaxis® magnetic sensor technology, we have made a significant step forward in robot tactile sensors, providing a rugged and competitive multi-axis sensing solution. We will now use the Tactaxis prototype as the foundation for further development work.”