Tektronix IsoVu TIVP Series, Руководство пользователя

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IsoVu measurement system block diagram
The following figure shows a block diagram of the IsoVu measurement system.
Figure 13: Block diagram
The common mode resistance and capacitance to earth ground is shown in the figure. The common mode resistance is
shown as R parasitic and is essentially infinite with the IsoVu measurement system since it is galvanically isolated and can
be ignored. The common mode coupling capacitance to earth ground and the surrounding circuit is shown as the Parasitic
Bridging Capacitance (C parasitic). This parasitic capacitance will be approximately 2 pF when the sensor head is placed
six (6) inches (15.25 cm) above a ground plane.
To minimize the effects of common mode capacitive loading consider the following items:
• Whenever possible, choose a reference point in the circuit-under-test that is static potential with respect to earth ground.
• Connect the coaxial (common) shield of the sensor tip cable to the lowest impedance point of the circuit.
• Increasing the physical distance between the sensor head and any conductive surface will reduce the parasitic
capacitance.
• When using multiple IsoVu systems to measure different points in the circuit that do not have the same common mode
voltages, keep the sensor heads separated to minimize the capacitive coupling.
Reference information
TIVP Series IsoVuTM Measurement System User Manual 40