Precision shunts

Fluke has introduced the A40B precision current shunt set, a range of precision devices designed to simplify the task of making current measurements in the laboratory.

The set comprises 14 low-inductance coaxial shunts, adapters and connectors and a transit/storage case.

Designed for currents from 1 mA to 100 A, the shunts are for laboratory use in making directly measured absolute AC or DC current measurements as well as DC/DC current transfer measurements.

They let users directly measure current with higher accuracy than is normally available because of their resistance value stability, self-heating power coefficient and low temperature coefficient.

Users can make precision measurements in a single step, rather than by more complex traditional AC/DC transfer methods.

The physical construction and the components used in the current shunts ensure that the frequency response is flat (amplitude displacement error relative to DC resistance). The phase displacement at 100 kHz is negligible in all but the highest accuracy measurements.

With their DC resistance stability, the shunts can be used to directly measure current through their full bandwidth.

They are suitable for traditional precision current applications such as calibrator verification and the wide current range allows verification of high current transconductance amplifiers.

The shunts are available in four different sizes. The full set includes: four fully enclosed shunts — 1, 10, 20, 50 mA; five small size radial shunts — 100, 200, 500 mA, 1 and 2 A; three medium size radial shunts — 5, 10, 20 A; two large size radial shunts — 50, 100 A.

Voltage output is nominally 0.8 V for the nominal rated current input. The output is measured by a voltmeter or detector, such as precision voltmeters, AC measurement standards, AC/DC transfer standards, or thermal voltage converters, fitting them to a wide variety of metrology applications.

Shunt resistance is designed to minimise interaction with detector instrumentation. The radial-style shunt design gives high performance with minimal external magnetic fields. The open nature of the physical design maximises airflow so the shunts have minimal power coefficient effects. This permits each shunt to be used over a wide range of currents with stable resistance characteristics.