Agilent Technologies InfiniiVision 7000B Series Guide de l'utilisateur télécharger pdf (Page 387)

100

101

Digital Channels 13

InfiniiVision Oscilloscopes User’s Guide 387

Probe Grounding

A probe ground is the low-impedance path for current to return to the source from the

probe. Increased length in this path will, at high frequencies, create large common mode

voltages at the probe input. The voltage generated behaves as if this path were an

inductor according to the equation:

Increasing the ground inductance (L), increasing the current (di) or decreasing the

transition time (dt), will all result in increasing the voltage (V). When this voltage exceeds

the threshold voltage defined in the oscilloscope, a false data measurement will occur.

Sharing one probe ground with many probes forces all the current that flows into each

probe to return through the same common ground inductance of the probe whose ground

return is used. The result is increased current (di) in the above equation, and, depending

on the transition time (dt), the common mode voltage may increase to a level that causes

false data generation.

Common Mode Input Voltage Model

In addition to the common mode voltage, longer ground returns also degrade the pulse

fidelity of the probe system. Rise time is increased, and ringing, due to the undamped LC

circuit at the input of the probe, is also increased. Because the digital channels display

-----

Probe 1

L (GND)

Probe 2

Probe N

(Common Mode)

Probe

Ground

1 2 ... 382 383 384 385 386 387 388 389 390 391 392 ... 427 428

Commentaires sur ces manuels

Pas de commentaire

Agilent Technologies InfiniiVision 7000B Series Guide de l'utilisateur Page 387

Commentaires sur ces manuels

Produits connexes et manuels pour Mesure, test et contrôle Agilent Technologies InfiniiVision 7000B Series