Ground Lead Inductance - Tektronix 2212 User Manual

Probes
Probe Connection
Generally, the probes supplied with the instrument provide the
most convenient way of connecting a signal to the vertical inputs of
the oscilloscope.
The standard accessory probe is a compensated
lOX
voltage divider.
It is a resistive voltage divider for low frequencies and a capacitive
voltage divider for high-frequency signal components. The VOL TS/
DIV scale factors, displayed on the crt readout, reflect the probe
attenuation factor when a Tektronix coded probe is used.
The probe and probe lead are shielded to prevent pickup of stray
electromagnetic interference, and the lOX attenuation factor of the
probe offers a high input impedance that minimizes loading in the
circuitry under test.
The way you attach your probe to a signal source can affect the
results you get. Two important factors that can affect your signal
are:
Ground lead inductance (introduced by the probe).
Misadjustment of the probe compensation.
Ground Lead Inductance
The probe's ground lead provides the best grounding method for
signal interconnection and ensures the maximum amount of signal
shielding in the probe cable. You can make reliable signal measure-
ments when the 2212 and the Unit Under Test are connected by a
common reference (ground lead) in addition to the signal lead or
probe. A separate ground lead can also be connected from the unit
under test to the oscilloscope ground receptacle located on the front
panel.
To get the best waveform fidility, keep the probe ground and signal
leads as short as possible. Inductance introduced by either a long
signal lead or ground lead forms a series-resonant circuit. This cir-
cuit will affect the system bandwidth and it will cause ringing if
driven by a signal containing frequency components at or near the
circuit's resonant frequency. Oscillations (ringing) can then appear
on the oscilloscope waveform display, distorting the true signal
waveshape.
2212 User Manual
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