Calculating frequency in RPM with JAVA

**gvBlake** · 23-08-2008

Hello,

I want to calculate the frequency of the signal from a computer fan which should be convertible to RPM in Java. Instead of using Counter-function, i would like to use analog input and i think this should be possible as i could get a proper square wave in LJscope. I want to know that how to start some kind of timer for this application.

The signal will be periodic and i know that i must sample it in the interval of some time. Can i check if it is Rising edge or Falling edge?

**kelfro** · 23-08-2008

As you are using analog input, some frequency determining software has to be written which will process the waveform. It seems like you are working on U12. You have one option of feeding a signal through FFT, which is at the bottom graph of LJscope. Second option of processing the data point by point, looking for a threshold or a change of slope.

**gvBlake** · 23-08-2008

Yeah, I am using the U12

. As you said about calculating FFT, i need to study that more clearly. Or some other methods of calculating frequency in RPM should be found out that are existing.