How Probes Affect Measurements - Tektronix TDS1000B Series Operator's Manual

How Probes Affect Measurements

To display a signal on an oscilloscope, the signal is diverted
to the oscilloscope input circuit. Depending on the relative
impedance values, the addition of a probe to a test point can
cause loading of the signal source. This topic describes the
loading effects of probes on signals. These effects are
caused by probe impedance interacting with the signal
source impedance.
Signal Source Impedance
The value of the signal source impedance influences the
effect of probe loading. For example, with low source
impedance, a high-impedance 10X probe can have a
negligible loading effect. However, for high source
impedances, the signal at the test point can change
significantly due to the probe. This change in the signal is
because the probe impedance is connected in parallel with
the circuit impedance.
TDS1000B and TDS2000B Series Oscilloscopes – Operator Training Kit
Introduction to Oscilloscopes and Probes
1
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