Question
Which of the following is good practice when using an oscilloscope probe?
Answer Options
- A) Minimize the length of the probe’s ground connection
- B) Never use a high-impedance probe to measure a low-impedance circuit
- C) Never use a DC-coupled probe to measure an AC circuit
- D) All these choices are correct
Correct Answer: A
Explanation
An oscilloscope probe and its ground lead can easily pick up noise or introduce stray inductance into the measured circuit, especially at higher radio frequencies. This pickup or added inductance can severely distort the waveform being measured and lead to false readings. Good probing technique is vital for accurate high-frequency measurements.
The most important good practice, particularly when measuring high-frequency signals or fast rise times, is to minimize the length of the probe’s ground connection. Using a short ground connection (sometimes a short spring clip or special adapter is necessary instead of the long pigtail lead) drastically reduces the loop area that can pick up RF noise and minimizes the series inductance that can distort the waveform’s transient response.
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