RPM on Mitsubishi FX2N

Hi guys...

I am using mitsubishi FX2N and i want to display RPM of some rollers ... I am able to sense the pulse/revolution by this function
spd X00 k100 D00
but the problem i am facing is the calculation of rpm after this funtion... I am using this formula for calculating rpm as per manual says
(D00 * 60) * 1000/ n * t
n is the pulses/revolution which is 6 and the t is mentioned as a measurment time. I am using the same value which has been used in the function i.e the refreshing time which is K100 100ms... but putting this value i am not getting the rpm and when it is multiplying by 1000 it changes the result in negative:S is this formula right?? and about the values?

Thanks in advance

(D00 * 60) * 1000/ n * t

example

1pulse * 60 * (1000/600) = 0

1000/600 =approx 0,4 = but with integers = 0 result is 0

change to this instead :

(D00 * 60 * 1000)/ (n * t)

exampel 1 pulse * 60 * 1000 = 60 000/600 = 100rpm

Explanation:

When calculating with integers always do the divide part last..

value you get in D0 is never negative number. Everything else is also positive (60, 1000, 6, 0.1) so it's pretty hard to get negative result.

i suspect you are either not calculating RPM in correct order or use incorrect register size which results in overflow (large values that sets sign bit making result negative).

Thank you guys for your valuable feedback...
here i would like to mention that i found this formula (D00 * 60) * 1000/ n * t from the mitsubishi manual. But i tried the both this and that the another you tell i.e (D00 * 60 * 1000)/ (n * t)...
for example in this case if i put the refreshing time k1000 which is 1sec i am getting 9-10 pulses and after calculation with the above formula we get 90, which is not the correct rpm... the correct rpm which i m getting from the digital rpm meter is around 360-400...
if i put the refreshing time k100 which is 0.1 sec i m getting 2 pulses and the result will be 200 which is also not correct...
Thanks for your assistance

The formula i described is exactly the same as the one in the manual to bad that they forgot to mention that if we dont have floating point numbers the equation will fail..

When you get 90 as result the equation is doing its job correctly if you had 9-10 pulses in..

Are you sure that the data for the pulses/rev is correct and are you sure that every pulse gets detected by the PLC?? And are the thingy that creates the pulses directly attached to the rollers or is there a transmission if that is you have compute that to..

Is it possible to drive really slow and se if the results is correct then?