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A40B Series Precision DC and AC Current Shunts

Precision, low inductance shunts for dc and ac current metrology

The A40B dc and ac precision current shunt set consists of 14 low-inductance coaxial current shunts, adapters and connectors, and a rugged transit/storage case. Designed for currents from 1 mA to 100A, the current shunts are for laboratory use in making directly measured absolute ac or dc current measurements as well as ac/dc current transfer measurements. They exhibit outstanding resistance value stability, with an excellent self-heating power coefficient, and a low temperature coefficient. With all of these characteristics combined, the shunts offer direct measurement of current from dc to 100 kHz with higher accuracy than previous commercially available shunt technology. Now precision measurements can be made in a single step process rather than by more complex traditional ac/dc transfer methods.

Product Description

  • Simplifies calibration/verification of precision calibrators and current sources
  • Shunts sized for currents from 1mA to 100A
  • Usable from dc to 100 kHz
  • 14 individual dc and ac current shunts with a 1, 2, 5 sequence over 6 decades of current
  • Simple direct measurements, making ac/dc transfers unnecessary
  • Stability typically better then ± 5.0 µΩ/Ω for one year
  • Typical angular accuracy of better than ± 0.003º at 1 kHz


The wide range of shunt values permit measuring from 0.1 mA to 100 Amps. 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). Also 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 as the complex ac/dc transfer measurement process will no longer be necessary for many precision current measurement applications. These characteristics make the A40B shunts ideal for traditional precision current applications such as calibrator verification. Also, the wide current range allows verification of high current transconductance amplifiers. 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.

Technical overview

The shunts come in four different sizes. The full current shunt set includes:

  • four fully enclosed dc and ac current shunts: 1 mA, 10 mA, 20 mA, 50 mA
  • five small size radial dc and ac current shunts: 100 mA, 200 mA, 500 mA, 1 A, 2 A
  • three medium size radial dc and ac current shunts: 5A, 10 A, 20 A
  • two large size radial dc and ac current shunts: 50 A, 100 A

Voltage output is nominally 0.8 volts 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.

The radial style dc and ac current shunt design gives high performance with minimum external magnetic fields. Plus, the open nature of the dc and ac current shunt physical design maximizes air flow so the shunts have a minimal power coefficient effects. This permits each shunt to be used over a wide range of currents with stable resistance characteristics.

The dc and ac current shunt resistance is designed to minimize interaction with the detector instrumentation. The 100 Amp shunt resistance is 8 milliohms, with shunt resistance increasing to 80 ohms for the 10 mA shunt. Additionally, the 1mA shunt includes an internal battery operated buffer amplifier. It drives the output voltage so the 800 ohm shunt resistance has minimal interaction with the measurement device.

Reports of calibration

The A40B series of precision DC and AC Current Shunts come with an ISO 17025 Accredited Certificate of Calibration.