Data acquisition Oscilloscope FFT MEMS SCB68A

[Gregory88]

Hey Guys,

i have a Mems Sensor Adxl335 and a Ni SCB68A to get my signals digitalized. I wanna messure the frequency through a tipicaly oscilloscope with a fft.

So far i made this with the DAQ-assistent and i can see the voltage/signal on the waveform but

Problem 1: after using the trigger, my signal gets lost and also the fft doesn´t look like it should(no idea which kind fft i have there 😕 ).

Problem 2: i cant get/see a zig-zag line from the vibration from my sensor in the graph like it is created in the diagram (maybe increase by a multiplicator the peak-to-peak voltage?)

Problem 3: best case would be, when i can see or select in this real time graph the period of the movement from the Mems-Sensor but this can maybe created by a trigger...

Thanks for you help.

[Gregory88]

Someone have an idea? 😞

[RamonaL]

Hi Gregory,

your programm is not using any LabVIEW Style Guides. You are not using any dataflow programming and it is a bit confuse.

I think it would make more sense if you take a look at the example vis, they basically have the same functionality like your vi in great parts, but they are much cleaner and easier to understand.

A really nice example for data acquistion can be found under Help>Find Examples> Hardware Input and Output > DAQmx>Analog Input>Voltage - continuous Input.vi. If you use another daq type, just go through the expamles, I am sure you will find the appropiate one.

This one I mention has the option to trigger the acquistion and also to log the data. As you can see its relativly simple and clean. In the While-Loop you could add your fft or any other functionality.

I hope this gives you a good starting point,

Ramona

[Gregory88]

Thank you very much Ramona,

so far it is working as expected, but isnt there a VI which uses the Express-Tools`? With this style i understand it much more easier. This would be

What is your opinon about this one:

https://www.youtube.com/watch?v=vkEg7P3oPvs

This function of this would be so perfect an the one i am looking for.

[RamonaL]

We don't provide examples with Express-VIs.

Of course you can use them. I still recommend you to use LabVIEW Style Guides and dataflow.

I dont know what you want to do, so I cant really suggest you anything else.

You should also have a look into the Eventstructure, as this would help you to have a clean structure. You can create events based on buttons so you wouldn't need to use that many case structures.

Here are some pretty good tutorials you could go through to learn a bit more: http://www.ni.com/academic/students/learn/

There is also a chapter about DAQ, so this might help you to understand a bit better how LabVIEW works.

Cheers, Ramona