Historically, engineers have been very creative when it comes to measuring current, and today there's a wide diversity of techniques used. However, when the application requires very high accuracy - such as power analysers, medical equipment and power supplies used in large scientific research establishments - zero-flux technology, also called 'fluxgate', is accepted as the best solution. Of the many commonly used current-sensing technologies, there are two main methods: one, based on Ohm's Law, uses a precision resistor called a "shunt" in parallel with the meter. This is a relatively simple approach, but doesn't provide very high accuracy and is subject to temperature-drift errors. The second approach uses the magnetic field generated by the current. This method can be used to measure AC - as with a current transformer, or AC and also DC. Zero-flux technology is a part of this second family of test methods.
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