Noise generation, FRF measurement

[splee]

I would like to do a FRF measurement of a mechanical system (not sound, not vibration)

In order to do this, I need to:

1. generate noise, and feed it to the input of my mechanical system

2. measure the input (noise) and output simultaneously. Collect the data

3. Use the collected data to compute FRF

So,

1. Is there any NI hardware, and LabVIEW block, which allows me to generate/output noise to my system

2. Is there any data logging hardware? It should be able to log the input, and output value, both of which are analog

[dsb@NI]

How are you using the noise to excite your mechanical system? Do you have a shaker or some other transducer to convert the noise to a force (or other) input?

What is the form of the output? What sensors are you using to measure the output of the mechanical system?

Will you wrap the stimulus signal back to one of the input channels?

[splee]

Hi,

The noise would be input to a motor driver, to drive the motor.

The output would be the motor speed, which is in the form of analog voltage (we can convert rpm to volts)

And for the question "Will you wrap the stimulus signal back to one of the input channels?", I suppose you mean do I need to measure the noise input? The answer is yes. I need to measure the noise input.

It would be better if, on top of the noise, I can have a d.c of +5V, for example.

[dsb@NI]

Even though you are not measuring vibration, it sounds like you are performing measurements of dynamic signals. Even if you don't have the Sound and Vibration Toolkit, install the evaluation and check out the Averaged Frequency Response (DAQmx) example. From the description:

This VI generates and acquires data for an averaged frequency response measurement. This VI performs a continuous acquisition and stops when the averaged measurement is complete. You specify the initial settling time of the device under test and the averaging parameters to use for the frequency response measurement. 

You can easily add DC offset to the excitation signal. You can use the SV example as a template to build your own VI where you can replace the SV VIs with general LV VIs. While you have it installed, you may also want to check out the SVL Measure Propagation Delay VI to measure the propagation delay between your motor drive input and the resulting output speed as you may need to account for this delay.

[splee]

So, what NI hardware board do I need, in order to generate noise?

Preferrably a cheaper option