Problem with Spectral Measurement (FFT)

[Kremschen]

Dear Community,

I am using a torque transducer which give me also the speed of the axis. This signal is a rectangle signal which 60 Imp/rad . I want the frequency of this signal for getting the speed. I am using the express Spectral Measurment. But unfortumatly it just give me the time. I produced with signal simulator a comparable signal and it works. I don't anderstand why!?

And a second question. If it would work would it be possible to get the frequency not just shown in a graph then in a value to work with it?

Lokking forward to answers.

Best Melina

[GerdW]

Hi Melina,

I don't anderstand why!?

It's all your fault! 😄

Either use DDT wires all over your VI - or don't use them at all. Mixing them with lots of conversion from/to "standard" datatypes is always "calling for problems"!

By converting the measurement data to 2D array you are basically stripping any timing information. Then you convert back to DDT and so add default timing information (dt=1)! All this just to split a single signal - why not use SplitSignal instead???

Edit: why do you split this signal at all? There is only one channel configured in your DAQAssistent!!!

(But in general I recommend to stay away from ExpressVIs and DDT wires as soon as possible…)

get the frequency not just shown in a graph then in a value to work with it?

Sure!

THINK DATAFLOW! The data you need is in a wire. When you need the data in several places you just need to branch the wire…

[Kremschen]

Dear GerdW

Thanks for your answer.

Sure you are right I am missing timing information. I will try it again in another way.

The program I add is just a compressed version. The original programm is much bigger and would be very confusing if I just want to get rid of this problem. The rest is working. I have a lot of other Signals reading in from other sensors thats the reason I'd try to split them. I did't know about a SplitSignal option yet. I will try to figure it out.

I am not a good programmer because I haven't learned it from the beginning I just crush in .

If I get it to run I will let you know.

Thanks !

Melina