500 MHz bandwidth, inductive current shunt measures fast switching to 250A

May 27, 2014 // By Graham Prophet
This inductive current shunt enables current measurements of very high bandwidth, in the range 160 kHz-500 MHz. It is available with a range of full-scale measuring ranges of extending up to ±250A. It introduces essentially zero resistance into the measured current path, and inductance of only 300 pH.

This inductive current shunt enables current measurements of very high bandwidth, in the range 160 kHz-500 MHz. It is available with a range of full-scale measuring ranges of extending up to ±250A. It introduces essentially zero resistance into the measured current path, and inductance of only 300 pH.

The measurement shunt is a product of Fraunhofer Institute for Reliability and Microintegration IZM, in Berlin. You might use it for precision measurement of any current, particularly large currents that are subject to high-speed transients, in power electronics. A specific application is characterising the switching behaviour of high-speed power semiconductor devices, such as the latest silicon carbide and gallium nitride parts.

It is an active, inductive current shunt. The pictures show how the “primary” coil – a slotted cylinder forming a single turn – is soldered to bridge a gap in a wide PCB conductor. A Rogowski coil sits within the cylindrical element, and the signal processing within the probe carries out integration to produce the signal that you can then view with a conventional oscilloscope connection.

 

As a metallic, slotted cylinder, shunt resistance is negligible and inductance added to the measured-current path is 300 pH. Peak voltage isolation is up to 5 kV; slew rate is 5.5 V/nsec; power supply is 5Vdc and the probe outputs a full-scale ±0.8V signal to a scope from an SMB connection, for termination into a 50Ω input. The measurement is made at high impedance to minimise any influence on the measured current.

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