Tektronix Thermometer P7225 Uživatelský manuál stáhnout pdf (Strana 35)

Operating Basics

P7225 2.5 GHz 10X Active Probe User Manual

source

Probe C

≤0.8 pF

(ground lead)

Figure 7: Ground lead equivalent circuit

Ringing and rise time degradation can be masked if the frequency

content of the signal degradation is beyond the bandwidth of the host

instrument.

You can determine if ground lead effects may be a problem in your

application if you know the sel f-inductance (L) and capacitance (C)

of your probe and ground lead. Calcul ate the approximate resonant

frequency (f

) at which this parasitic circuit will resonate with the

following formula:

2π LC



The preceding equation shows that reducing the ground l ead

inductance will raise the resonant frequency. If your measurements

are affected by ringing, lower the i nductance of your ground path

until the resulting resonant frequency is well above the frequency of

your measurements.

The low-inductance ground pogo pin described in Features and

Accessories starting on page 5 can hel p you reduce the e ffects of

ground lead inductance on your measurements.

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Tektronix Thermometer P7225 Uživatelský manuál Strana 35