Counter/Timer
PCI-6602, How to convert Pulse Width to RPM and stop updating datalogging at 30 RPM
Hi all,
My objective is to stop updating data logging pulse width measurements at 30 RPM so I can record the time lenght it takes the RPMs to stop from 6000 to 30 RPM. When I turn off the tool. I have an encoder attached to an output shat of a 6000 RPM circular saw. I have created 3 program methods, but I was not able to stop at 30 RPM. The last pulse width value the data log updates is around 200 RPM. I don't know if I'm using the right method to read RPMs?
System:
1) NI-PCI 6602 Counter/Timer Card
2) SBC-60 Connector Block
3) TRD-S1000-VD Encoder. 1000 PPR
4) LabVIEW 8.5.1
5) PC Dell Precision T3400 (32-bit), Intel Core Quad 2.4GHz, Memory 2GB. Windows XP prof.
In method 1: I reading pulse width and converted to RPM with this formula. RPM = 60/(1000 PPR/ Pulse Width).
In method 2: I just measuring pulse width and try to stop while loop when pulse width value is greater than 0.002 mSec. by using this formula 60sec/30rpm = 2 sec/rev, 1 Rev = 1000 counts. Therefore, 2 Sec / 1000 Counts = 2 mSec/Cnt (0.002)
In method 3: I measuring pulse width using this formula, Pulse Width (in Sec) = Count/Counter Timebase Rate (20MHz), One period is 1000 cnts X 0.002mSec = 2. Therefore, Pulse Width = 2 / 20MGz = 0.000000100
All three methods stop recording pulses around 200 rpm. I wonder if the formulas I utilizing, are not using them properly. Or there is floating point number conversion???? Please See attached Picture.
Any help is greatly appreciated. THANKS!!!
Carlos G.
