data-acquisition.us

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Common-mode voltage is defined as the voltage between a signal and the localized common, which is usually earth ground. Common-mode voltages can be quite high, depending on the signal source. For example, a current sensing shunt in a dc motor drive might be expected to be at line-voltage potential, although the actual signal level is less than 50 mV across the shunt terminals. Measurement techniques for small signals at high common mode potentials call for isolation.
Isolation transformer
Power switching circuit using SCR’s or MOSFET transistors
Internal drive control common
Speed adjustment potentiometer

Topic: Isolation and Noise Reduction