Description
Description-Separate-1I am attempting to read angular velocity off of a magnetic pickup (60 toothed) using an NI 9361 counter card. I have compared a few different VIs out there and I am confused at the phenomemon they are generating. For refrence I have an anolog tachometer coupled together so I can read the actual (analog) RPM and compare it to my digital NI values. It seems at low RPMs (0 to 6k) that the floor of the data plotted is closely in line with the analog RPM and has a lot of noise. At higher RPMs the values are much more stable. However, at higher RPMs there are still spikes which throws off my mean calculation by a few hundred compared with the analog value. I have used a bandstop filter with a low cutoff of 200Hz and high cutoff of 1000 hz and that seems to be fixing the spiking issue although not entirely. I have attached some pictures of the problem at 4k RPM, at 10k RPM, and my VI for reference. If I decrease the sample rate it just about eliminates the noise but it still has a degraded accuracy at the lower RPMs. Can anyone help me with the lower frequencies RPM and/or recommend a solution to read a more consitant RPM in a range of 0 to 50k RPM? Any insight would be appreciated.
Description-Separate-2
