First ASIC-based closed-loop current transducer

Citation

(1999), "First ASIC-based closed-loop current transducer", Sensor Review, Vol. 19 No. 1. https://doi.org/10.1108/sr.1999.08719aad.003

First ASIC-based closed-loop current transducer

First ASIC-based closed-loop current transducer

Keywords Currents, Transducers

As the latest innovation in transducer technology LEM now introduces the LTS 25-NP, a closed-loop current transducer capable of measuring DC, AC and impulse currents with inherent galvanic isolation (see Plate 3). The transducer offers a multi-range configuration designed for accurate measurement of nominal currents of 8, 12 or 25A rms. Different connection options are integrated allowing users to make direct or differential current measurement. As a further advantage the LTS 25-NP features a measuring range of more than three times I_N; thus peak currents up to 25, 38 and 80A respectively can be measured. By integrating the whole electronics in a specific ASIC, the LEM engineers have succeeded in combining a particularly high performance with an extremely compact size.

Plate 3 The new LTS 25-NP, capable of measuring DC, AC and impulse currents with inherent galvanic isolation

Owing to the innovative technology employed, the LTS 25-NP offers a performance that was not possible to achieve up to now with traditional hall effect closed loop transducers. In addition to its miniature size (9.3 × 22.2 × 24mm), the LTS 25-NP has an intrinsic accuracy of ± 0.2 per cent, an excellent linearity of less than 0.025 per cent and a bandwidth from DC to 200kHz. The use of the integrated circuit means that the LTS25-NP also has a very low temperature drift of only 50ppm/C° typically.

Also new with this concept, the LTS 25-NP is supplied with a unipolar power supply of +5V, while still capable of measuring both positive and negative currents by use of an offset zero. Therefore the need for a dual rail supply is eliminated. In addition, a measuring resistor of 0.5 per cent accuracy has been incorporated which directly provides a voltage output for further processing characterised by a very low temperature drift. The output is set at 2.5V for zero primary current with a span of 0.625V at nominal current. Thus the transducer can directly be connected to the 5V input of microcontrollers, A/D converters and instrumentation cards.

All of these features make the product easier to design into drives or control systems and provide a significant saving in costs.

The LTS 25-NP complies with the IEC 664-1 standards as well as European directives EMC 89/336/EEC and LVD 72/23/CEE.

For more information, contact Neil Hayden, LEM UK Limited, Geneva Court, 1 Penketh Place, West Pimbo, Skelmersdale WN8 9QX, UK. Tel: +44 (0)1695 720777.