Interrupts jumps on rpm measure

[garg29]

Dear All,

I am measuring 2 rpms through INT0 and INT1 both simultaneously.
But i am getting lot of jumps in rpm value .:sad:
Please help me out .

 

[wp100]

Hi

Sorry Crystal Ball down for a while :-D

You need to say what make and type of chip you are using, which compiler and post your code and circuit so we can see whats happening.

Its more normal to measure rpm via the Capture function as explained here
This uses a timer to count the pulses, whereas your INT0 method will be interrupting every pulse so its likely your interrupts may overtake each other and so give incorrect readings.

 

[horace1]

what is you expected RPM and how long a time period are you measuring over?
e.g. if the RPM is low (say a few revs a second) and you measure over a too short time period (say half a second) the counted revs will vary in RPM value depending on the number of counts in the time slot