LEM has introduced at SPS new sensors for AC and DC isolated-current measurement with the introduction of the HMSR series. Despite their small size, the components can handle overload current bursts of up to 20 kA (8-20 µs surge test profile), such as those that occur in photovoltaics applications while still providing a reinforced isolation. Products in the series are designed to measure currents of up to 2.5 times their nominal ratings of 6 A, 8 A, 10 A, 15 A, 20 A or 30 A.

Packaged as SO16 surface-mount devices with a height of just 6 mm, the sensors can be mounted directly onto a printed circuit board in the same process as other board-level components. This helps to reduce manufacturing costs and decrease the overall footprint, vital for space-constrained applications. As a result, HMSR sensors can be readily built into small form-factor intelligent power modules (IPMs). The HMSR series uses a proprietary Open Loop Hall effect ASIC associated with a low-resistance primary conductor to minimize power losses allowing DC measurement and high transient overload currents to pass without damage. The use of a ferrite for the magnetic element is a key factor in achieving a high frequency bandwidth of 270 kHz (-3dB) and to provide good rejection against external fields. An integrated EEPROM is used for programmable internal temperature compensation to counter offset and gain drifts and perform gain stress compensation. These measures ensure high-performance overall accuracy over the full range of temperature, from -40 to 125°C with a typical value of 0.5 % of IPN for the HMSR 20-SMS model, a significant improvement over the previous generation. The HMSR series achieves a shorter response time of 2 µs typical.

Additionally the company announced new Rogowski coils to measure current up to 300,000 A AC with accuracy class 0.5. The ARU range achieves IEC 61869-10 class 0.5 without the need for additional components such as resistors or potentiometers to calibrate the coil, which can drift over time. The range benefits from ‘Perfect Loop’ technology, a unique patented coil clasp that eliminates the inaccuracy caused by sensitivity to the position of the conductor inside the loop. This technology provides an innovative, robust and fast ‘Twist and Click’ closure.

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