LEM has extended its range of current transducer families designed to operate from a single +5V power supply with the introduction of the HMS model. The new unit measures 16 (L) x 13.5 (W) x 12 (H) mm and integrates a primary conductor. It is directly surface-mounted onto a printed circuit board. Four standard models are available to cover nominal AC, DC, pulsed and mixed isolated current measurement of 5, 10, 15 or 20 ARMS, up to 50 kHz, with a measuring span of up to ± 3 x IPN. The same mechanical design is used for all four models so that they can be used to measure current across a complete range of end products. The internal reference voltage (2.5V) is provided on a separate pin or can be forced by an external reference (between 2 and 2.8V) for reference thermal drift cancellation. Gain and offset are fixed and set so that, at Ipn, the output voltage is equal to Ref in or Ref out ± 0.625 V. A LEM ASIC designed for use with open-loop Hall-effect technology has been used to provide performance improvements. These include better offset and gain drifts and linearity, in addition to an extended operating temperature range (-40 to +85°C) compared to traditional discrete technology.

An additional version of the HMS transducer is being developed for PCB mounting through holes instead of surface mounting and will be available in the next few months. The transducers are CE marked, conform to the EN 50178 standard and are recognised for industrial applications such as home appliances, variable speed drives, UPS, SMPS, power inverters (solar, wind, etc) and air-conditioners.