Effect of low meter impedance on loop-antenna based measurements of magnetic fields

In using a simple loop-antenna for the measurement of low-frequency magnetic fields, systematic errors (of the order of 20%) could arise if a low impedance (50 Omega ) meter is substituted in lieu of a high-impedance type. Nonconsideration of this error in recommended measurement practices and procedures (such as the SAE specification) for radiated emissions is indicated. Theoretical results indicating the systematic error computed over a frequency range of 30 Hz to 25 KHz are presented. Supporting experimental data concerning the loop impedance measurements and the difference in loop-antenna output voltage noticed with low and high impedance meters confirm the theoretical elucidations.<
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