LEM has introduced Minisens, a miniature, integrated circuit transducer for ac and dc isolated current measurement up to 100kHz. This new component offers full isolation (no optocouplers required) and high sensitivity (from 20 mV to 200 mV per Amp of primary current) with no insertion losses. It is mounted directly on a printed circuit board as an SMD device, reducing manufacturing cost.
Minisens integrates, within one mixed signal ASIC, Hall-effect sensors with a magnetic concentrator to allow direct current measurement without the need for an additional magnetic core. The non-contact measurement enables an almost unlimited current level as it eliminates the need for current to flow through the device. The only limiting factor is the thermal capacities of the primary conductor. The current can be carried either by a track (or tracks) located on a PCB underneath the Minisens, or by a cable or bus bar under or above the IC. The unlimited design possibilities for the primary conductor allow current measurement up to 70 A or even higher.
Many parameters of the ASIC can be configured by on-chip non-volatile memory: adjustment of the transducer’s gain, offset, polarity, temperature drift and gain algorithm (proportional to, or independent of VDD). Two outputs are available: one filtered, to limit the noise bandwidth; and one unfiltered, which has a response time of less than 3 microseconds.
The Minisens operates from a single 5V supply. To minimise power consumption an optional input pin can be used to switch the Minisens into standby mode. The transducer is manufactured with a CMOS process and assembled in a SO8-IC package.
The combination of different IC configurations and flexible PCB designs results in very versatile and attractively priced current transducer solutions. This opens up opportunities for applications such as white goods or air conditioning to benefit from isolated current measurement, which previously was not feasible. Minisens will also enable enhanced motor control to produce energy savings where other methods such as the shunt have traditionally been used.