Introduction
Active probes and passive probes are two commonly used probe types in electronic measurements. They connect to different signal sources and have distinct characteristics, advantages, and limitations. This article explains the differences between them.
Definition
Active probe: An active probe contains a built-in amplifier. It can be connected directly to a signal source and amplify the signal. It is typically used for measuring higher voltages and larger currents, and in applications such as oscilloscopes, power supplies, and switching power supplies.
Passive probe: A passive probe does not include a built-in amplifier and cannot directly amplify a signal. It must be used with an external amplifier. It is typically used for measuring lower voltages and smaller currents, for example with temperature sensors and pressure sensors.
Operating principle
Active probes integrate an amplifier inside the probe. The input signal is capacitively coupled to the probe front end, amplified by the internal amplifier, and then sent to an oscilloscope or other measurement instrument for display and analysis.
Passive probes do not have an internal amplifier. The input signal is transmitted to the probe via resistive coupling, and subsequent circuitry performs processing and amplification before the signal is output to an oscilloscope or other measurement instrument for display and analysis.
Comparison of advantages and disadvantages
1. Measurement range
Active probes, with their internal amplifiers, can measure higher voltages and larger currents, offering a wider measurement range. Passive probes are typically limited to lower voltages and smaller currents, so their measurement range is narrower.
2. Cost
Active probes include amplifiers, which increases manufacturing complexity and cost, so they are generally more expensive. Passive probes are comparatively less costly.
3. Ease of use
Active probes are more convenient to use because they include the amplifier and usually do not require additional external equipment. Passive probes require an external amplifier to perform similar tasks, which can make setup more involved.
4. Accuracy and resolution
Active probes, due to their built-in amplification, generally offer higher accuracy and better resolution, meeting a wider range of measurement needs. Passive probes typically provide lower accuracy and resolution and are suitable for simpler measurement tasks.
Application scenarios
Active probes are appropriate for measuring higher voltages and larger currents in scenarios such as oscilloscopes, power supplies, and switching power supplies. Passive probes are suitable for measuring lower voltages and smaller currents, for example with temperature sensors and pressure sensors.
Conclusion
Both active and passive probes are common in electronic measurement, but they have different characteristics, advantages, and limitations. Selection should be based on the specific measurement requirements and the intended application scenario.
