Noise Rejection - Keysight 34450A Guia Del Usuario

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.
Common Mode Rejection (CMR)
Ideally, a multimeter is completely isolated from earth-referenced circuits.
However, there is finite resistance between the multimeter's input LO terminal and
earth ground, as shown below. This can cause errors when measuring low
voltages which are floating relative to earth ground.
Figure 3-1
Keysight 34450A User's Guide
Common Mode Rejection (CMR)
Measurement Tutorial 3
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