# How to find Area of Hysteresis?

• I

Homework Helper
welcome to PF;
hint: use calculus.

• SDRFG
SDRFG
how to use calculus here i have never done .

Staff Emeritus
Homework Helper
how to use calculus here i have never done .
Then why do you need to know the area of the hysteresis loop?

• SDRFG
SDRFG
Then why do you need to know the area of the hysteresis loop?

I have studied calculus but no idea how too apply ?

Homework Helper
Since you have studied calculus, you known how to use it to find the area under a curve.
That is pretty much the definition of "integration".

Perhaps if you ptovided an example?

• SDRFG
I have studied calculus but no idea how too apply ?

Does this ring any bells?

• SDRFG
Gold Member
If the hysteresis loop is plotted from test data then there will be no immediately available equations defining the shape of the up going and down going curves forming the loop .

To use calculus you need to find the equations of curves which are best fit to the plot curves . There are standard ways of doing this .

Alternatively you can use numerical methods . There are standard ways of doing this also .

• SDRFG
Gold Member
Numerical methods :

(1) Overlay the plot onto squared paper . Count the number of squares enclosed by the loop . Use a rule to decide when to include or exclude partial squares .

(2) Divide the plot into many slices with equally spaced horizontal or vertical lines . Estimate the area in each slice and sum .

(3) If you want to get more sophisticated look up : Trapezium Rule , Simpson's Rule and Gaussian Quadrature .

(Have a look at Gaussian Quadrature anyway for general interest - it is fascinating how a very small number of ordinate samples can give very accurate answers)

• SDRFG
Gold Member
When I started in the DO we sometimes used a Planimeter . Now we use facilities within our CAD software .

There are downloadable apps for working out areas enclosed by curves .

• SDRFG
SDRFG
OK, How to find equation of curve?

SDRFG
hello i understand planimeter

houlahound
You could weigh the paper any calibrate it to the area. Fun experimental/hands on way to integrate without calculus, kids love it and you can talk about error.

Gold Member
The easy way :

http://uk.mathworks.com/products/curvefitting/

http://uk.mathworks.com/videos/curve-fitting-toolbox-overview-61198.html

(You can do the integration in Mathworks as well if you want to)

The moderately easy way :

Choose simple functions which give the right sort of curve shapes to fit your plot and scale them to best fit . Sometimes easier to break plot curve into segments and use different functions for each segment .

Commonly used functions : linear , polynomial , exponential and sine/cosine .

Slightly more formal way :

https://en.wikipedia.org/wiki/Curve_fitting#Fitting_lines_and_polynomial_functions_to_data_points

• SDRFG
Gold Member
• SDRFG
SDRFG
hello,

How to drawn second degree polynomial, like this?

Staff Emeritus
How to drawn second degree polynomial, like this?
SDRFG, can you attach a neat plot of your hysteresis loop, with the measured points clearly shown?

Do you intend using a software package to find a polynomial of best fit? (I expect wolfram alpha would do this for you.)

• SDRFG
SDRFG
i want to learn by hand in paper

Staff Emeritus
i want to learn by hand in paper

• SDRFG
SDRFG
I dont have any plot it was in college i left it over 3 year completing degree. they dnt guide properly may be lack of information.

Staff Emeritus
I dont have any plot it was in college i left it over 3 year completing degree. they dnt guide properly may be lack of information.
That's okay. It's obviously a matter that piqued your interest at the time, and you kept it in mind should the opportunity later present itself to pursue it further.

Here's your opportunity. What would you like to do in this thread at this point?

• SDRFG
SDRFG
Here's your opportunity. What would you like to do in this thread at this point?
At class i was not aware of it, but while teaching for few days on it it attract me.
and without this basic i cant move further it involve practical math.

Staff Emeritus
So what would you like to be the next step in this thread today?

You are happy with the answers you have received so far? Can we assist you further?

• SDRFG
SDRFG
yes, i get my answer you can assist further.

Homework Helper
If you have a set of data points, you can fit a polynomial to that set by using "least squares regression".
Google for: "least squares curve fitting lecture", and see if you can find a lesson that suits you. ie.
http://web.iitd.ac.in/~pmvs/courses/mel705/curvefitting.pdf
It's not just a quick howto - and it takes practise.

If you have ever done linear regression, it is like that only for curves.

It is usually quite time consuming so most people will use a computer to do this - usually matlab, octave, or mathatica.
https://www.gnu.org/software/octave/

Apart from that: how can we assist you further?

• SDRFG • 