Test & Measurement


Precision current shunts

25 November 2009 Test & Measurement

The Fluke A40B precision current shunts are designed to simplify and improve metrology for DC and AC current. Used to measure current from 1 mA to 100 A, the shunts ensure reliable and traceable results.

For many applications, improved resistor technology enables users to make accurate AC current measurements in a single step, instead of using traditional, more complex AC/DC transfer methods.

Intended for broad coverage of current measurement applications, the A40B set consists of 14 low-inductance coaxial current shunts, leads, adapters and connectors, plus a rugged case for transit and storage. Together they cover a wide workload that includes electrical calibrators, electrical power standards, current sources, transconductance amplifiers and more. The entire set can be purchased or individual shunts as required.

The physical construction and the components used in the current shunts ensure that the frequency response is very flat (amplitude displacement error relative to DC resistance). The phase displacement at 100 kHz is small enough to be neglected in all but the highest accuracy measurements. Combined with excellent DC resistance stability, the shunts can be used to directly measure current through their full bandwidth. This simplifies precision AC current measurements, so the complex AC/DC transfer measurement process will no longer be necessary for many precision current measurement applications.

The low phase shift error is critical for measurement of non-sinusoidal wave shapes, as found in power quality or sampling digital wattmeter measurement applications. The A40B current shunts feature a radial design for high performance with minimum interference from external magnetic fields. The open design maximises air flow so the shunts have minimal power coefficient effects, enabling them to be used over a wide range of currents with stable resistance; an external cooling fan is not required. The 4-terminal design completely isolates measured voltage from extraneous current path resistance. Current does not flow in the voltage circuit, allowing users to measure with the highest accuracy.

Optional adapters allow for connections with commonly used N connectors as well as LC connectors for high-current applications. The 1 mA shunt includes an internal battery-operated buffer amplifier to isolate the voltage measurement circuit from the current circuit. This enables the user to use the shunt to make low-current measurements at optimal voltage levels, while eliminating the effects of input impedance of the measurement device.

The shunts’ output voltage is nominal at 0,8 V, making them compatible with a wide range of devices including precision digital multimeters, AC-DC transfer standards, AC measurement standards, thermal voltage converters and sampling digital multimeters. Low inductance and low phase displacement make the A40B shunts an excellent fit for power measurement or digital sampling wattmeter measurement applications where phase accuracy and stability are critical. The wide current range allows verification of high-current transconductance amplifiers.





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