Open-loop Hall-effect user-programmable current transducers up to 25A DC, AC or pulsed

May 10, 2012 // By Julien Happich
LEM announced the HO series of open-loop ASIC based current transducers, set to deliver better performance in areas such as thermal drift, response time, power supply and noise driven by technology advances in power electronics applications.

The HO series measures AC, DC or pulsed currents with a nominal value of 8, 15 or 25 ARMS, with a response time of 2 to 6 μs. Both of these parameters, and several others, are user-programmable by a simple serial digital bit-sequence, generated by the system's host microcontroller. Other parameters that are user-programmable include reference voltage, over-current detection limits, fault reporting and low power mode. The unit delivers its output as a scaled analogue voltage; in most systems this will be converted to a digital value by an analogue/digital converter (ADC) which requires a reference voltage. The designer can program the LEM HO-series transducer to output a reference of 0.5, 1.5, 1.65 or 2.5V on a dedicated pin. Alternatively, the HO-series can be configured to make measurements relative to an external reference. The current transducer achieves a typical accuracy of 1% and 2.8%, at +25°C and +85°, respectively, without offset, and with a high level of insulation between primary and measurement circuits.

An innovative feature of the HO series is programmable over-current detection, separate from the main current measurement. Using a single measurement range (for both detection and measuring functions), if the transducer must detect an over-current condition at (say) five times the nominal full-scale value, the measurement range must extend up to the over-current limit, reducing available accuracy within the nominal range. Separate over-current detection, with programmable threshold, ensures maximum resolution is maintained up to the nominal full-scale value.

The HO-series transducer operates from a single supply voltage at 3.3 or 5V. It comes in a PCB-mountable 12x23x12mm package which incorporates three separate primary conductors to allow for multi-range measurement configurations (enabling nominal measurement as low as 2.67 ARMS when programmed at 8 ARMS for the nominal range). Versions of the HO-series transducers will be available for both through-hole and surface-mount assembly. The operating temperature range is -40 to +115°C.

Visit LEM at www.lem.com