Noise Rejection
Rejecting Power–Line Noise Voltages
A desirable characteristic of integrating analog–to–digital (A/D) converters is their ability to reject power– line related noise present with DC input signals. This is called normal mode noise rejection, or NMR. The multimeter achieves NMR by measuring the average DC input by "integrating" it over a fixed period. If you set the integration time to a whole number of power line cycles (PLCs), these errors (and their harmonics) will average out to approximately zero.
The multimeter provides three integration selections (1, 10, and 100 PLCs) that achieve NMR. The multimeter measures the power–line frequency (50 Hz or 60 Hz), and then determines the corresponding integration time. For a complete listing of NMR, approximate added rms noise, reading rate, and resolution for each integration setting, see the Performance vs. Integration Time table.
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