New instrument provides high accuracy isolated current measurements in the 1000A range using fluxgate technology.

High Current Fluxgate Sensors

varies hugely from the most basic forms of instruments through to the highly precise sensors available today for ensuring the most accurate measurement of electric currents in critical applications. The latest model in power electronics specialist LEM International’s range of high accuracy transducers is the IN 1000-S, a product similar to the recently introduced 2000A fluxgate technology measuring instrument. The IN 1000-S is ideal for non-intrusive and isolated measurement of DC, AC and pulsed nominal currents of 1000 A with an accuracy of 0.0018%, the highest in the company’s range of products.


WIDER APPLICATION A key factor in the development process for the new instrument was to take its applicability beyond laboratories into the less controlled environments in industry. With temperature ranges of between +10°C and +50°C usually being offered with such instruments, LEM International extended this range on the IN 1000-S enabling it to be used at temperatures down to -40°C or as high as +85°C without detrimental effect on its capabilities. Increasing the scope for its use opened

lthough a well established method of measuring vector magnetic fields, fluxgate sensing technology

up markets in areas that had specific requirements for such high accuracy current measurement, including the medical industry, motion control, robotics and test & measurement. In healthcare alone, the accurate measurement of high currents plays a significant role in the production of high quality output from medical imaging systems such as Magnetic Resonance Imaging (MRI)

DIGITAL PROCESSING For the IN 1000-S, LEM International took a fresh approach to an established technology to achieve unprecedented levels of accuracy. Signal processing is performed in the digital domain and a new approach to fluxgate technology architecture has been applied resulting in ripple cancellation of the fluxgate drive frequency. The result is a compact transducer, maintaining its high accuracy over a wider temperature range, with reduced noise level vs the previous generation, according to LEM. By processing the signal on the digital side of the instrument after the ADC, complete immunity to temperature effects, interference and supply voltage variations is achieved. This contributes to offset and offset drift improvements.

RIPPLE REDUCTION The reduction of the interference or ripple from the fluxgate driving signal at a fixed frequency is as a result of the use

❱ ❱ The high accuracy 1000A fluxgate transducer can be used outside the lab in industrial and healthcare applications

of the DSP (Digital Signal Processor). Higher frequency harmonics have been reduced. The remaining interference has been eliminated by driving a ‘ripple compensation coil’, whose amplitude and phase are adjusted during the calibration of each transducer. After calibration, the remaining peak-to-peak ripple is less than 34ppm, relative to the full-scale transducer output, over the full operating temperature range. As a result of these innovations, the IN 1000-S has high performance across the extended temperature range, delivering extremely high accuracy with linearity and low offset over the whole range.

FLEXIBLE SET UP The IN 1000-S has been designed to be flexible in the way that it’s used. It operates from a bipolar +/-15 V DC power supply and will accommodate round primary conductors of up to 38.2 mm diameter. In addition to its normal current output, the transducer offers an additional output indicating the transducer state (low or high output levels) and an external LED showing normal operation. An equivalent product would usually be made up of 2 parts, the measuring head and the treatment electronics, while this new model has a compact integrated design allowing different mounting options. n

DAQ, Sensors & Instrumentation Vol 1 No. 2 /// 13

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