Modifying Oscilloscope to Measure Pulse Frequency of Phototransistor

[fowlerd8]

My goal is to measure the RPM of an AC motor that runs a chopper blade.  I have been browsing online, and have seen various oscilloscope models, but they all seem to just be function generators that generates an artificial signal.  Is there a way to modify these Oscilloscope VI's so that instead of generating a signal, I can use an AI module, say the NI 9215, to measure the voltage across a resistor?  That voltage would be the phototransistor pulse frequency, hence why I need an oscilloscope.  Linked is a VI that was shared on YouTube, credit: Kuldeep Singh.  https://www.youtube.com/watch?v=ru1KFyL9Tgo

[GerdW]

Hi fowler,

I have been browsing online, and have seen various oscilloscope models, but they all seem to just be function generators that generates an artificial signal.

Scopes usually don't "generate" signals, instead they measure them…

I can use an AI module, say the NI 9215, to measure the voltage across a resistor?

Sure you can use such a DAQ module.

LabVIEW comes with a huge example library, including (DAQmx) examples on how to measure voltages!

Btw. I would suggest a DAQ device being able to count pulses, most digital inputs support that. Now you just need  to read the pulse count to calculate a frequency from that. (The better digital input DAQ devices even deliver frequency values directly. I mostly use cheap USB600x boxes or a cRIO/FPGA/NI9403 combination.)

[fowlerd8]

Thanks GerdW,

I didn't phrase it well, I meant that the oscilloscope was just reading the function generated signals, whereas I want the signals acquired from the phototransistor.  Since my post, I changed my mind.  Considering this schematic

I am thinking about using the NI 9423 DI to count the pulses generated.  But that's about as far as I can get, any first steps I can take? 

[GerdW]

Hi fowler,

please attach images here in the forum instead of linking to 3rd party websites!

any first steps I can take?

Do the training as offered in the LabVIEW forum.

Look at the example VIs/projects coming with LabVIEW.