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Oscilloscope Passive Probes Vs Active Probes

WTS
24 October 2018 13:40

 Scope Probes Passive Vs. Active Banner

Oscilloscope Passive Probes Vs Active Probes

The importance of probe selection can significantly affect your measurement and accuracy. Learn and benefit from a better understanding of Oscilloscope Probes and how to select the correct probe for specific measurement tasks. The area we look to explore and explain is the difference between passive and active oscilloscope probes.

1 - What is a Passive (Modular) Probe?

2 - What are The Advantages of Passive (Modular) Probes?

3 - What are The Disadvantages of Passive (Modular) Probes?

4 - What is an Active Probe?

5 - What are The Advantages of Active Probes?

6 - What are The Disadvantages of Active Probes?

7 - Conclusion: Passive Probes Vs. Active Probes

 

1 - What is a Passive (Modular) Probe?

Passive (Modular) Probes: are the most common type of oscilloscope probe and characterised by their rugged and economical nature. These probes are what the industry considers as “general purpose” probes. There are two major categories of passive probes;

  1. High-impedance-input passive probes
  2. Low-impedance, resistor-divider passive probes

“for most applications a x10 attenuation scope probe is the best all round type of probe”

    6493 Passive Probe 150 MHz x10                  6495 Passive Probe 250 MHz x10                  6498 Passive Probe 350 MHz x100

 Passive Scope Probe 150MHz           Passive Scope Probe 250MHz           6498 Scope Passive Probe 350MHz

Example applications:

  • Probing emitter-coupled logic (ECL) circuits
  • Microwave applications
  • Transmission lines

2 - What are The Advantages of Passive (Modular) Probes?

  • Low capacitive loading
  • Very high bandwidth
  • Sufficient to make quick quantitative measurements
  • Rugged
  • Low-cost

3 - What are The Disadvantages of Passive (Modular) Probes?

  • Relatively heavy resistive loading that can affect the measured amplitude of the signal
  • Insufficient for qualitative measurement where high level accuracy is required

4 - What is an Active Probe?

Active probes: are a level above passive probes in terms of performance, complexity, and cost. Generally, active probes are purchased separately from an oscilloscope and used for a specific measurement application. Active probes have opposite characteristics to the rugged passive probes. The internal circuits inside the probe tend to be fragile and need carful handling. Differential scope probes are a form of specialised active probe that are commonly used to measure differential signals, such as; low level audio and disk drive signals.

“Although many active probes in the market have an impressive bandwidth specification, remember that the real-world performance of an active probe is dominated primarily by how you connect the probe to the target.”

TT-SI-9001 Active Probe               TT-SI-9010 Active Probe               TT-SI-9002 Active Probe

Testec Active Scope Probe                  Testec Active Test Probe                 TT-SI-9002 Active Scope Probe

5 - What are the Advantages of Active Probes?

  • Probe of choice when high-bandwidth performance is required
  • Significantly lower capacitive loading – greater accuracy insight into fast signals
  • Higher Bandwidth than passive probes
  • Superior level of performance in comparison to Passive Probes

6 - What are the Disadvantages of Active Probes?

  • Input voltage is typically limited
  • Typically cost more than passive probes
  • Requires probe power

7 - Conclusion: Passive Probes Vs. Active Probes?

Oscilloscope probes are an essential addition to any oscilloscope, although there is no clear-cut winner when it comes to Passive Probes Vs Active Probes, as it depends on your intended application.

Probe selection does affect measurement accuracy and signal integrity. Passive probes work well at low-frequencies, although as soon as you attempt to measure a higher frequency signal you will experience a significant degradation of performance. Next time you attempt a measurement, consider signal speed and the type of measurement you’re trying to make and choose either probe accordingly. If, however you need a general purpose probe we would suggest an x10 attenuation scope probe for most applications.

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