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.