In recent years

the rapid development of new-type power system and quantum measurement technologies has imposed more stringent requirements on the sensitivity and accuracy of wide-bandwidth

wide-dynamic-range current metrology in field environments. This paper surveys three current-measurement approaches based on magnetic sensing principles and quantum effects: alkali-vapor optically pumped magnetometers(OPMs)

superconducting quantum interference device(SQUID)-based cryogenic current comparators(CCCs)

and diamond nitrogen-vacancy(NV)-center sensors. OPMs

operating at room temperature with vapor cells typically heated to 50~150 ℃

exploit atomic spin precession and can achieve fT·Hz−1/2 magnetic-field sensitivity; in practice they enable current measurements from the milliampere to ampere scale over DC to several kilohertz. SQUID-based systems

leveraging flux quantization and the Josephson effect

can reach aT·Hz−1/2 magnetic sensitivity under adequate magnetic shielding and optimized pickup-coil design. With suitable turns ratios and flux-locked-loop feedback

their measurable current range spans picoamperes to amperes

and they can deliver metrological accuracy from DC up to the megahertz band. NV-center sensors

based on optically detected magnetic resonance(ODMR) with microwave control and optical readout

routinely achieve pT·Hz−1/2 sensitivity. In non-contact current sensing configurations

the upper measurable current reaches the kiloampere range. Continuous-mode bandwidth typically covers DC to the kilohertz range

while narrowband AC readout at a fixed carrier frequency can extend the center frequency into the megahertz regime. By comparing the underlying mechanisms

key performance metrics

and engineering challenges

we conclude: OPMs must improve noise immunity and system integration to better withstand complex field environments; SQUID/CCC systems are constrained by cryogenic cooling and cost

motivating miniaturization and simplified maintenance; and although NV sensors are somewhat less sensitive

their electrical insulation and compact form factor offer clear advantages for non-contact measurements in high-voltage

high-current settings.