Hall-effect current transducers

Test & Measurement

15 May 2013 Test & Measurement

LEM’s new HLSR series of current transducers aims to provide a cost-effective and technically superior alternative to resistive shunt/optocoupler configurations for insulated current measurements up to 50 A.

The five new parts will satisfy application requirements in, for example, industrial inverters and motor drives; switch-mode and uninterruptible power supplies; specialist power supplies such as welding units; air conditioning; home appliances; and also in renewable energy systems, for example, in solar combiner boxes and in solar inverters to track the maximum power point (MPPT).

The HLSR series uses open-loop Hall-effect current sensing technology to measure AC, DC or pulsed currents with nominal values of 10, 20, 32, 40 or 50 ARMS. This technology allows these devices to achieve a response time of only 2,5 s, with very low gain and offset drift over their operating temperature range of -40°C to +105°C.

The transducers deliver their output as an analog voltage proportional to the primary measured current. In most applications, this voltage will be converted to a digital value by an analog-to-digital converter: LEM has equipped the HLSR with an internal voltage reference of 1,65 or 2,5 V made available on a dedicated pin for use by an external device such as an A-D converter, for example, or designers can choose to use an external reference from 0,5 to 2,65 V.

The voltage reference is just one feature of the new ASIC (application-specific integrated circuit) that LEM’s designers created for this development, which enables the HLSR series to deliver typical accuracy of ±1% at +25°C, and ±3,4% at +105°C, with a bandwidth of 100 kHz (-3 dB). LEM offers versions that operate from either 3,3 V or 5 V single supplies.

The transducers are packaged in a compact outline that occupies only 387 mm² of PCB area. Variants of the package cater for either surface-mount or through-hole connection of both primary conductor path and signal/power connections. The low-profile package weighs just 5,5 g, and is less than 12 mm high.

Safe measurements are assured with a high level of insulation between primary and measurement circuitry thanks to long creepage and clearance distances (8 mm as standard and 14 mm on request), and a comparative tracking index (CTI) of 600. HLSR transducers are CE marked, conform to the EN 50178 standard for industrial applications, and come with a five-year warranty.

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