Choosing Probes
Two problems arise when you use a probe to connect an oscilloscope to a
circuit. First, the probe degrades the circuit under test. The new circuit
behaves differently than does the circuit without the probe. The behavior
you see is the behavior of the circuit with the probe. Second, the transfer
function of the probe is part of the overall measurement system response,
degrading measurement accuracy.
The probe is a part of the circuit under test
Suppose that you are trying to debug an intermittent failure in a state
machine that is implemented in high-speed CMOS logic. You know that you
need a high-performance digitizing oscilloscope, but you don’t know which
probe gives the best results.
There are two major factors influencing probe selection: the load the probe
imposes on the circuit, and the required bandwidth of the circuit with the
probe.
Figure 1-7
How the Oscilloscope Works
Choosing Probes
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