AC and DC Current

NI Digital Waveform Generator/Analyzer Help

Edition Date: June 2013

Part Number: 370520P-01

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AC current is current sourced/sunk during the transition between low and high level states driving a capacitive load (such as a cable) or an inductive load (such as a device interconnect). DC current is the current sourced/sunk when the generation terminals are at a static voltage driving a resistive load. The following illustration of a digital waveform shows when AC or DC current is sourced/sunk.

Digital waveform showing periods of AC and DC current flow.

Use the following formulas to calculate AC current:

where    I is current in amps,

C is load capacitance in farads

dV/dt is the rate of change of the voltage level in volts/s

or

where    I is the current in amps

L is the inductive loading in henrys

V(t) is the voltage in volts as a function of time

Use the following formula to calculate DC current:

where    I is current in amps

V is voltage level in volts

R is resistance in ohms

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