Bode Plots - phase plotting by hand

[FrogPad]

My notes from lecture are somewhat deceiving. I have this table that is supposed to make plotting the phase portion of a Bode plot simple. I understand the magnitude portion, however I do not get what is being said for the phase portion. I am spending too much time on something that is supposed to be straightforward, so I'm just going to ask...

Could someone explain how to plot straight line approximations of the phase portion of a Bode plot to me? Or point me to a website that shows a straightforward method?

 

[FrogPad]

I found an amazing piece of MATLAB code that has helped me through my problem.

It can be found here:
http://www.swarthmore.edu/NatSci/echeeve1/Ref/LPSA/Bode/BodeFiles.html


It shows individual straight line approximations that would be drawn just like a human would, the summation of these straight lines, and the exact magnitude and phase on the plot. VERY NICE!

 

[piercas]

Sure, I can help explain how to plot the phase portion of a Bode plot. The phase portion of a Bode plot represents the phase shift of a system's output compared to its input at different frequencies. To plot this, you will need to first determine the phase shift at different frequencies using the table you mentioned. This table usually includes the frequency, phase shift in degrees, and the corresponding phase shift in radians.

To plot the phase portion, you will need to use a semi-log graph with the frequency on the x-axis and the phase shift on the y-axis. The phase shift should be plotted in degrees, with positive values representing a lag and negative values representing a lead.

To plot straight line approximations, you will need to look for regions where the phase shift is changing at a constant rate. These regions will appear as straight lines on the graph. Once you have identified these regions, you can draw a straight line connecting the points on the graph.

It is important to note that the straight line approximations are only an approximation and may not accurately represent the actual phase shift at a particular frequency. However, they can provide a good visual representation of the phase shift behavior of a system.

I hope this helps to clarify the process of plotting the phase portion of a Bode plot. If you need further assistance, there are many online resources available that provide step-by-step instructions and examples. Just make sure to double check the information to ensure its accuracy. Good luck with your plotting!