Use max or min functions

Michel @ Am getting the same output after using max or min... can you please explain how to use it

if it is a sine wave with no offset voltage, then the max and min functions will give you the same result (with the sign difference). When you have your signal in a vector x for example, just use max(x) to get the peak value.

Use max then find operators

i.e.,

t = 1:0.001:2;%sec

f = 2 %Hz ;

A = 1 %Volt

x = A* sin(2*pi*t*f);

plot(t,x)

peaks = max(x)

index = find(x==peaks)

Dear Vivekanandan Kandiannan, If you further need to clarify or need the tool thenj check the following link.

http://www.mathworks.com/matlabcentral/fileexchange/11755-peak-finding-and-measurement

thanx Olaa & afaq

I had another choice... We can use Fourier Block.. it show the maximum values...

Dear Vivekanandan Kandiannan,, you are most welcomed.

if you want the true-rms value of a sampled (noisy or distorted) signal x, you can try

sqrt(sum(x.*x)/size(x)). Have a good day!

Dear Vivekanandan Kandiannan! First question is: From where does your sinewave come ? If you have sinewave from any sensor or other real object (e.g. voltage from power grid 50/60Hz) , you have a lot disturbance too. In this case you can't use max or/and min functions, becouse you will get a large measurement errors. In this case you can calculate the RMS-value of signal (like Claudio Bruzzese wrote above), and next you must multiply RMS-value by factor equal sqrt(2) to obtain amplitude. Next question is: how many time do you have to measure amplitude of signal? One period of signal? Or more - it's simply. Or less - it's very dificult, but possible.

Please clarify if u r using

matlab or simulink

Dear Eligiusz Pawlowski And Sunil Manjani...! I have already mentioned in question its a voltage waveform (Sinewave), it is generated using PMSG in matlab.

You need to check if the multimeter used in the lab reads true r.m.s or average; a multimeter does not read the voltage peaks.

Dear Neil O'Kelly! Actually its my mistake, I mentioned peak values instead of r.m.s.

So, if your voltage waveform (Sinewave) is generated using PMSG (in matlab or real generator), you must measure True R.M.S. (not peak or average value), I think. In power generation is important RMS voltage mainly because the power and energy depends on the RMS value of voltage. For this reason all the better voltmeters measure the RMS value. However, worse voltmeters measure the average value, but the display shows the RMS value too (they multiply the average value by the 1.111 - sine wave form factor).

You can calculate the RMS-value of signal like Claudio Bruzzese wrote above:

sqrt(sum(x.*x)/size(x)), but size(x) must be exactly equal to one period (or to integral multiple) of signal.

So, you need to know the period (or frequency) of the voltage signal too.

Eligiusz Pawlowski @ How to develop a simulation block to measure the RMS values on matlab, for the sinewave from PMSG

There are many different possibilities. I suggest you read an interesting discussion:

http://www.edaboard.com/thread163664.html

and this documentation :

http://www.mathworks.com/help/physmod/sps/powersys/ref/rms.html

Regards

Thanks to everyone I had the same question and now approaching towards the solution depending upon the above discussion........