Calculating Cutoff Frequency with Oscilloscope and Coaxial Cable

In summary, the conversation discusses the process of calculating the cutoff frequency for a system involving an oscilloscope with an impedance of R=1M Ohm // C=25pF and a coaxial cable with an impedance of R=75 Ohm, C=68pF/m with L=0.85m, and C=57.8pF. The question is whether the capacitors in the system are arranged in series or parallel, with the suggestion that the coaxial cable's construction as two conductors suggests a parallel arrangement. The conversation ends with a request for confirmation of this assumption.
  • #1
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First take a look at the attachment (See reply below). We have to take the oscilloscope's impedance and the coaxial cable's impedance into account. And then we have to calculate the cutoff frequency of this.
Given: Oscilloscope: R=1M Ohm // C=25pF
Coaxial Cable: R=75 Ohm and C=68pF/m with L=0.85m
C=57.8pF

My problem is that I don't know how to draw this. R and C from the Coaxial cable, are they serial or parallel? And the coaxial cable's impedance is that serial or parallel to the oscilloscope's impedance?

If I know that, I can calculate the cutoff frequency and the voltages with different frequencies, but now I'm stuck. Thanks in advance.
 
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  • #2
Attachment

And here's the attachment :).
 

Attachments

  • cutofffreq.jpg
    cutofffreq.jpg
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  • #3
Anyone? Or is my question not clear enough?
 
  • #4
Here's a hint: What is a capacitor? In asking this I'm prodding you into thinking about how a capicitor is physically made from there you should be able to figure out the problem. Also, do you know what a coaxial cable is and how it is constructed? If you don't know google it. If you do know, think about the construction of the coax cable and that of a capacitor. Good Luck
 
  • #5
Well a capacitor is actually two charged conductors very close to each other, so there's a voltage difference between them, right? And a coaxial Cable has an inner and an outer conductor, so those two conductors are responsible for the capacitance. That means the capacitance has to be parallel, right?

SO it has to be one of this two schemes (attached)?
Only I'm not sure which one...
 

Attachments

  • cutoffreq2.jpg
    cutoffreq2.jpg
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FAQ: Calculating Cutoff Frequency with Oscilloscope and Coaxial Cable

What is the purpose of calculating cutoff frequency with an oscilloscope and coaxial cable?

The purpose of calculating cutoff frequency with an oscilloscope and coaxial cable is to determine the point at which a signal or waveform starts to degrade or attenuate. This information is important in designing and troubleshooting electronic circuits and systems.

What is the theory behind calculating cutoff frequency?

Calculating cutoff frequency involves understanding the properties of capacitors and inductors in a circuit. Capacitors store and release energy in the form of an electric field, while inductors store and release energy in the form of a magnetic field. Together, these components create a resonant frequency, which is the frequency at which the signal begins to attenuate.

What equipment is needed to calculate cutoff frequency with an oscilloscope and coaxial cable?

To calculate cutoff frequency, you will need an oscilloscope, a function generator, a coaxial cable, and various connectors and adapters. The oscilloscope is used to measure the voltage of the signal, while the function generator is used to generate a signal of varying frequencies. The coaxial cable is used to connect the two devices.

What are the steps for calculating cutoff frequency with an oscilloscope and coaxial cable?

The first step is to connect the function generator to the oscilloscope using the coaxial cable. Then, adjust the function generator to produce a sine wave signal. Next, increase the frequency of the signal until the amplitude on the oscilloscope starts to decrease. The frequency at which this occurs is the cutoff frequency.

Are there any limitations to calculating cutoff frequency with an oscilloscope and coaxial cable?

Yes, there are a few limitations to keep in mind. First, the accuracy of the measurement may be affected by the quality and length of the coaxial cable. Additionally, the impedance of the oscilloscope and function generator must match for accurate results. Finally, the measurement may be affected by external noise or interference.

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