LEM Hall Effect current sensors are available in open-loop, closed-loop and Eta configurations. Open-loop Hall Effect sensors are highly cost effective, as well as being small and consuming minimal power. Closed-loop sensors offer higher accuracy and enhanced speed to enable currents with a wider range of frequencies to be measured.
Hall Effect Eta transducers are similar in construction to closed loop transducers , with the same magnetic circuit geometry, a Hall generator and secondary winding. A Hall Effect Eta transducer is a mix of open loop and current transformer technologies operating as an open loop transducer at low frequencies (up to 2…10 kHz depending on the specific transducer design), and as a current transformer at higher frequencies. Both the Hall Effect and transformer signals are electronically added to form a common output signal.
A “standard” closed-loop Fluxgate sensor uses a secondary winding to counteract the field generated in a magnetic circuit by the primary conductor. Although similar in operation to a closed-loop Hall Effect sensor, the Fluxgate uses a saturable inductor using a small thin magnetic core to sense the airgap field, rather than a Hall Effect transducer.
Other Fluxgate transducers built on the technology to deliver specific benefits. They are:
The material used to create the core can limit the performance of the transducer due to characteristics such as remanence, hysteresis, non-linearity, losses and saturation. So the design of an air-core or coreless transducer is often considered.
Examples of air-core current sensors include Rogowski coil transducers.
For more information about different current transducer technologies, download Isolated Current and Voltage Transducers: Characteristics, Applications, Calculations.
To find a current transducer for your application, visit the LEM Current Transducer Selector Tool.