@article{Corcoran:2020:10.1109/tim.2019.2908509,
author = {Corcoran, J and Davies, CM and Cawley, P and Nagy, PB},
doi = {10.1109/tim.2019.2908509},
journal = {IEEE Transactions on Instrumentation and Measurement},
pages = {1313--1326},
title = {A quasi-DC potential drop measurement system for materials testing},
url = {http://dx.doi.org/10.1109/tim.2019.2908509},
volume = {69},
year = {2020}
}

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TY  - JOUR
AB  - Potential drop measurements are well established for use in materials testing and are commonly used for crack growth and strain monitoring. Traditionally, the experimenter has a choice between employing direct current (DC) or alternating current (AC), both of which have strengths and limitations. DC measurements are afflicted by competing spurious DC signals and therefore require large measurement currents (10’s or 100’s of amps) to improve the signal to noise ratio, which in turn leads to significant resistive Joule heating. AC measurements have superior noise performance due to utilisation of phase-sensitive detection and a lower spectral noise density, but are subject to the skin-effect and are therefore not well suited to high-accuracy scientific studies of ferromagnetic materials. In this work a quasi-DC monitoring system is presented which uses very low frequency (0.3-30 Hz) current which combines the positive attributes of both DC and AC while mitigating the negatives. Bespoke equipment has been developed that is capable of low-noise measurements in the demanding quasi-DC regime. A creep crack growth test and fatigue test are used to compare noise performance and measurement power against alternative DCPD equipment. The combination of the quasi-DC methodology and the specially designed electronics yields exceptionally low-noise measurements using typically 100-400 mA; at 400mA the quasi-DC system achieves a 13-fold improvement in signal to noise ratio compared to a 25A DC system. The reduction in measurement current from 25A to 400mA represents a ~3900 fold reduction in measurement power, effectively eliminating resistive heating and enabling much simpler experimental arrangements.
AU  - Corcoran,J
AU  - Davies,CM
AU  - Cawley,P
AU  - Nagy,PB
DO  - 10.1109/tim.2019.2908509
EP  - 1326
PY  - 2020///
SN  - 0018-9456
SP  - 1313
TI  - A quasi-DC potential drop measurement system for materials testing
T2  - IEEE Transactions on Instrumentation and Measurement
UR  - http://dx.doi.org/10.1109/tim.2019.2908509
UR  - http://hdl.handle.net/10044/1/68527
VL  - 69
ER  - 

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