Measuring the damping frequency from an oscilloscope reading

In summary: Yes, but you can't find it by removing the resistors in the original circuit. The natural frequency term appears automatically in the transfer function.
  • #1
Boltzman Oscillation
233
26
Homework Statement
From the oscilloscope reading, find the undamped frequency of oscillation, damped exponent, and damped frequency of oscillation if the damping ratio is .1.
Relevant Equations
shown below
I know the following equations for if the damping ratio is less than 1:
$$\sigma = -\zeta \omega_n$$
$$\omega = \sqrt{(1 - \zeta ^2)\omega^2_n}$$
I am given the following circuit that I built on LTSpice:
cirucit.png

Measuring the voltage between node 2 and ground (blue), and the voltage Vc4(t) (green) I get the following reading:
1570766890109.png

what is the undamped frequency of oscillation, damped exponent, and damped frequency of oscillation? All I really need is the undamped natural frequency because I will be able to use the formulas to find the rest. How can I find it? Is it just the frequency of the green signal? Vc4(t)?
 
Physics news on Phys.org
  • #2
The frequency of the green squiggle is the damped frequency of oscillation. You'd have to use your equation to solve for the undamped frequency.
 
  • Like
Likes Boltzman Oscillation
  • #3
Anachronist said:
The frequency of the green squiggle is the damped frequency of oscillation. You'd have to use your equation to solve for the undamped frequency.
Ah I guessed as much. In a critically damped scenario i get the following reading:
1570777882082.png

this time the blue line is my capacitor voltage. I am asked for the undamped frequency, is this just the frequency of the rising portion of the signal?
 
  • #4
Boltzman Oscillation said:
I am asked for the undamped frequency, is this just the frequency of the rising portion of the signal?
It is the natural frequency of the circuit i.e. the frequency with which the output would oscillate had there been no damping element(s).
 
  • #5
cnh1995 said:
It is the natural frequency of the circuit i.e. the frequency with which the output would oscillate had there been no damping element(s).
Ah so without the resistors.
 
  • #6
Boltzman Oscillation said:
Ah so without the resistors.
Yes, but you can't find it by removing the resistors in the original circuit. The natural frequency term appears automatically in the transfer function.
 
  • #7

FAQ: Measuring the damping frequency from an oscilloscope reading

1. What is damping frequency?

Damping frequency is the rate at which a system's oscillations decay over time due to the influence of outside forces or friction.

2. How is damping frequency measured from an oscilloscope reading?

To measure damping frequency from an oscilloscope reading, you need to first identify the peak amplitude of the oscillations on the screen. Then, use the timebase setting to measure the time it takes for the oscillations to decay to a specific percentage of the peak amplitude. The inverse of this time is the damping frequency.

3. What is the significance of measuring damping frequency?

Measuring damping frequency can provide valuable information about the level of damping in a system. This can help engineers and scientists understand and improve the performance of various mechanical and electrical systems.

4. What factors can affect the accuracy of measuring damping frequency?

The accuracy of measuring damping frequency can be affected by factors such as the sensitivity and calibration of the oscilloscope, external noise and interference, and the precision of the timebase setting. It is important to carefully control these factors to ensure accurate measurements.

5. Can damping frequency be calculated using other methods besides an oscilloscope?

Yes, damping frequency can also be calculated using other methods such as a frequency response analyzer or a mathematical model of the system. However, using an oscilloscope is a common and relatively simple method for measuring damping frequency in real-time.

Similar threads

Replies
5
Views
60K
Replies
1
Views
2K
Replies
4
Views
1K
Replies
3
Views
3K
Replies
10
Views
2K
Replies
1
Views
789
Back
Top