Temperature Compensated M-Shunts for Fast Transient and Low Inductive Current Measurements

Abstract:
Most current measurement techniques suffer from temperature impacts, though to a different degree. This is also true for shunt resistors, which are usually improved significantly by using temperature compensated alloy materials like Manganin(r) or by proper calibration and subsequent temperature compensation. The concept of the copper-based PCB M-shunt has already been reported to yield excellent current measurement results at room temperature. However, due to the high-temperature coefficient of copper (3920 ppm/K), the current measurement with those M-shunts showed considerable measurement errors for high temperatures and due to self-heating. This can be improved by the use of Manganin. However, still the connection of the resistor with the copper of the PCB and their respective thermal behavior needs to be considered as further possible sources of error. This paper presents challenges associated with the improvement of PCB-based shunts by temperature-compensated material, while not compromising the critical issue of bandwidth and manufacturing capability. It explicitly addresses the problems and difficulties as reported for previous development stages. In its new version, the M-shunt, represents a low inductance measurement system that can be optimised for much higher energies than the coax shunt, while not increasing the inductance introduced into the circuit. Alternatively, it can be configured for a significantly increased bandwidth and lower inductance compared to its coaxial reference.