Drop Tower Velocity Sensor

[jkessler]

Hi,

I am trying to use a NTE 3100 phototransistor as a velocity sensor for a impact tower and trigger for the collection of load data. I had a working prototype using analog inputs and the pulse measurement function; however, when I compared my results with a control I found that they were significantly too fast. I believe this is because the reference levels I am using exclude small tails on the analog pulses. When i try to bring the reference levels down to include to tails, noise in the signal causes premature triggering resulting is wildly high velocities. 

One idea is to switch to a digital input but the daqs I am working with are all analog (NI 9205 and 9203). I do have access to a NI 6259 which has DI/O pins but the pulse measurement function does not seem to work with digital signals and when I try to use a PFI pin/counter, weird things are happening to my circuit voltages. 

Another idea is to use some kind of high pass filter but I am very new to LabView and don't really know how to do either.

Any assistance is highly appreciated. The analog VI I have been using is attached.  

[Kevin_Price]

While the code is helpful too, it sounds like your main problem comes in while post-processing your data.  What'll help even more is to collect data on a typical-enough run (typical of the troublesome ones).   Then from the menu select "Edit-->Make Current Values Default".  Then resave and repost the vi, along with the output data file you saved.

The best suggestions will very much depend on both what your data looks like and what info you need to extract from it.  I *think* you only need a good measure of the pulse width, but let us know if you need anything more or different than that.

-Kevin P