Saturday, July 16, 2011
Passive Probe Types- An Overview
Voltage probes used in oscilloscopes are typically classified as active and passive probes. Passive probes are so named because it is indicative of the fact that this type of probe does not contain active elements like transistors inside them. Rather, a probe of this kind consists entirely of passive elements like resistors, inductors, cables and capacitors. Because of this, it is unable to provide amplification and thus it only gives the original signal amplitude of a material being tested to the measuring instrument.
One advantage of using passive probes on an oscilloscope is that there is no hard limit for the maximum voltage that the probe is able to handle. It is also an inexpensive option since its circuitry is relatively simple and it does not require a power supply. In addition to that, its passive nature prevents the addition of random noise to the signals being sent to the oscilloscope. Majority of probes used in oscilloscopes are of the passive kind.
Passive probes are typically categorized based upon the level of attenuation of the signal that the probes can provide. There are typically three classifications of passive probes each one depending on the attenuation ratio. Attenuation refers to the gradual loss of intensity of any type of flux that is travelling through a medium; in this case, the flux is the voltage of the circuit being tested. These types are generally 1X, 10X and 100X probes.
A 1X scope probe provides a 1:1 attenuation ratio. It is the simplest oscilloscope probe. As suggested by its name, this probe does not attenuate the voltage going through it. Its impedance input is oftentimes similar to that of the oscilloscope. This type of passive probe is made of a connector to the oscilloscope and a coax that is connected to actual probe. A 1X probe is mostly suited for low frequency applications. However, applications requiring greater accuracy and higher frequencies may not be suited for this type of probe.
Better accuracy at higher impedance levels are achieved more using 10X scope probes. This type of probe has attenuators attached to its end that can then connect to the circuit being tested. A 10X probe indicates that the probe attenuates the incoming voltage by a factor of ten. Technically, the signals entering the oscilloscope are reduced and this factor must therefore be taken considered when making measurements.
The third most common probe is 100X scope probes. Other values such as 20X and 1000X probes are also available but the 100X is the most popular choice after the 1X and 10X probes. This passive probe is useful when taking measurements of circuits with extremely high voltages as well as those circuits that need very low levels of loading. These probes are typically used for special purposes and are not commonly utilized for the average application. Because it attenuates the signal by a factor of 100, utilizing it in normal applications will result to significantly minute signal levels being input to the oscilloscope. As a result, extraneous and unwanted noise on the input amplifiers of said scope will be visible and this could lead to inaccuracies in the readings.
The types enumerated above are just some of the most common types of passive probes. Oftentimes, the task of choosing the best probe for an oscilloscope will depend on what is readily available. Being familiar with the requirements of the test as well as the specifications of the circuit to be tested are also vital in determining the most appropriate probe for the job. Basic knowledge of the different passive probe types however will go a long way in ensuring good and accurate results.
One advantage of using passive probes on an oscilloscope is that there is no hard limit for the maximum voltage that the probe is able to handle. It is also an inexpensive option since its circuitry is relatively simple and it does not require a power supply. In addition to that, its passive nature prevents the addition of random noise to the signals being sent to the oscilloscope. Majority of probes used in oscilloscopes are of the passive kind.
Passive probes are typically categorized based upon the level of attenuation of the signal that the probes can provide. There are typically three classifications of passive probes each one depending on the attenuation ratio. Attenuation refers to the gradual loss of intensity of any type of flux that is travelling through a medium; in this case, the flux is the voltage of the circuit being tested. These types are generally 1X, 10X and 100X probes.
A 1X scope probe provides a 1:1 attenuation ratio. It is the simplest oscilloscope probe. As suggested by its name, this probe does not attenuate the voltage going through it. Its impedance input is oftentimes similar to that of the oscilloscope. This type of passive probe is made of a connector to the oscilloscope and a coax that is connected to actual probe. A 1X probe is mostly suited for low frequency applications. However, applications requiring greater accuracy and higher frequencies may not be suited for this type of probe.
Better accuracy at higher impedance levels are achieved more using 10X scope probes. This type of probe has attenuators attached to its end that can then connect to the circuit being tested. A 10X probe indicates that the probe attenuates the incoming voltage by a factor of ten. Technically, the signals entering the oscilloscope are reduced and this factor must therefore be taken considered when making measurements.
The third most common probe is 100X scope probes. Other values such as 20X and 1000X probes are also available but the 100X is the most popular choice after the 1X and 10X probes. This passive probe is useful when taking measurements of circuits with extremely high voltages as well as those circuits that need very low levels of loading. These probes are typically used for special purposes and are not commonly utilized for the average application. Because it attenuates the signal by a factor of 100, utilizing it in normal applications will result to significantly minute signal levels being input to the oscilloscope. As a result, extraneous and unwanted noise on the input amplifiers of said scope will be visible and this could lead to inaccuracies in the readings.
The types enumerated above are just some of the most common types of passive probes. Oftentimes, the task of choosing the best probe for an oscilloscope will depend on what is readily available. Being familiar with the requirements of the test as well as the specifications of the circuit to be tested are also vital in determining the most appropriate probe for the job. Basic knowledge of the different passive probe types however will go a long way in ensuring good and accurate results.
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oscilloscope probe
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