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National Instruments NI USB-621x User Manual

Page 128

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Chapter 11

Isolation and Digital Isolators

NI USB-621x User Manual

11-4

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Add an AC return path from the device isolated ground to earth ground. For
non-isolated systems, an AC return path is only needed for high or source
impedances. An AC return path can be created by connecting a capacitor
between the device’s isolated ground and earth ground.