Comparator block in simulink

What is the block i can use in simulink that makes a comparison between two signals? I tried the block named "comparator" from "Simelectronics library" but it dosen't work because it doesn't enable connecting my inputs on it. thanks

[Subarna Giri]

I have same problem

Answer 1

[Jason Ghidella]

An alternative is to use the built-in block "Relational Operator" block from the Logic and Bit Operations library in Simulink. There are other blocks in the library that you may also what to use.

A piece of advice though is the watch out for data type issues. If you are comparing doubles then you may not always get the result you are expecting due to the floatign point precisions of your machince, (eps).

Here is a thread on this topic: http://www.mathworks.com/matlabcentral/newsreader/view_thread/66553

[Caroline Rosa]

thanks for your tip Jason

[santhiya Balachandar]

Thanks a lot

Answer 2

[Azzi Abdelmalek]

If you want to compare signal1 and signal2 use two block:

1. sum block to get signal1-signal2
2. compare to constant block where you will set constant value to 0. The input of this block is signal1-signal2

[Caroline Rosa]

Thanks Azzi.

[paranandi lakshmi narayana]

sir what is the use of the constant block.actually in my project need to compare 2 signals.Is sum block is enough or need use constant block if necessary how please explain me sir

[Boubker Boutalha]

Thanks Abdelmalek !

To @Paranandi Lakshmi Narayana , with the solution proposed by @Azzi Abdelmalek, you still compare the signals, it is just applied the differential comparison to a costant.

For example, your signals are A and B, that could be numbers. You could compare them directly, like as follow:

A > B ; A greater than B

Or instead applying the differential, you do the following:

A > B ----> (A - B) > (B - B) ----> (A - B) > 0 ;

So, tell that A is greater than B, correspond to have (A - B) greater than the constant 0 (zero).

Kind regards,

Boubker

[Wael Atiyah]

Dear Mr.Abdalmalek

your suggestion not clear wirh respect to me , possible more clarrification