Agilent Technologies 90B manual Ground Loops, Power Supply and Load Wiring Equivalent Circuits

travel down the load distribution wires and falsely trigger one of the other loads.

Figure 37. Power Supply and Load Wiring Equivalent Circuits

To be effective, the high frequency impedance of local decoupling capacitors C0, C1, C2, and C3 (Figure 38) must be lower than the impedance of wires connected to the same load. Thus a decoupling capacitor must be chosen with care, with full knowledge of its inductance and effective series resistance, as well as its capacitance. Moreover, it is imperative that the shortest possible leads be used to connect local decoupling capacitors directly to the load and DT terminals (not to other points along the dc wiring paths) so that the wiring impedance between the capacitor and its connection point is minimized.

Ground Loops

This is the most persistent, subtle, difficult-to-analyze, and generally troublesome problem connected with power supply wiring. The origins of ground loop problems are so diverse that empirical solutions are frequently resorted to. Nevertheless, a little extra thought and care will reduce, and in most cases eliminate, the need for an empirical approach.

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