Equal Percentage characteristic can be identified by equal increments of X axis that yield equal percentage increments of the y-axis.

Whereas, in a linear characteristic, equal increments of x-axis yield equal increments in the y-axis.

Linear curve is simple as equation is just y=x.

I need help for the equation for equal percentage curve.
Either equation or how to generate it in excel will be gr8.

I have posted this picture of both linear(1) and equal percentage curve(2)  which will tell you what I am asking.
Thanks in advance

Chanaa dai,

Actually this type of equation applies to flow charecteristics in control valve (In Hydraulics). I think there are different types of valves based on the charecteristics as fast opening, linear, equal percentage etc(actually I also forgot all, polera khaaiyo) In this equation,

Y = 0.02 e ^ (3.91X)

X is opening i.e 0 for 'close' and 1 for 'fully open' while Y is percentage rate of flow i.e 1 means fluid flowing in full capacity.

But I think those type of curves apply everywhere (I dont know others).

And Loots,

I just found out the constants based upon your quation. You have the right equation and if you watch my datas, you can find equal %(almost 48%) increase (not increment) with the equal % increment( not increase), IMO.  

BTW, I dont know the mathematical defintition of this 'Equal percentage curve' as I said in my first post I just like to apply mathematics but never done correctly.

Parbatya

don't worry dude,professor zee is always here for u..here is one hard math problem i recently solved

parbatya,
you rounded them numbers so i got diff. percentages when i calculated them (on my head). comes out to be 47.85% to be precise (with calc :P) so yeah that's one solution that you came up with.. Also n=4.0236 is the precise value in your solution (not 3.91), that will yield y=0.1 for x=0.4
----------

just to generalize this (for V2001 or for anyone who might be interested):

y=K.exp(nx)

the given condition, y=0.1 when x=40% can have multiple solutions for K and n.

putting these values in the above eqn:

n=[log(0.1)-log(K)]/0.4 (where log is a natural logarithm)

so based on your K, n is determined. To make sure it's a positive exponential curve (for positive increment), K<=0.1. Also to get real solution (not complex), K>0.

Hence 0<K<=0.1
Also, more the K, less will be your change in flow percentage (y%). Depending upon your requirement, K can be chosen and that will give n.

Let me tell you guys why I needed it. I work for a valve manufacturer and these linear and equal percent curve are to be dealt daily. But I was always confused with this curve.
Yesterday I realized that I was trying to generalize a specific curve.
Anyway, thanks to all of u. I will try to get some detail about the valve profile curve including mathematics behind it and will share with you guys if they turned out to be interesting.

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is sumansuman gone mad or trying to make us mad?