Using Analog Output on PCI 6221 to excite shaker

[Anil_Reddy]

Hi,

I need to excite a shaker by sending Signal from my application.

I am trying to use PCI 6221 card for this purpose. I will be connecting the signal coming from my DAQ card to a power amplifier and then to shaker.

I will be sending a sine wave or sweep sine wave with noise without noise.

Any suggestions on this?....can i go-ahead with this card?

Please let me know if someone has already done with this kind of application.

Thanks

Anil

[WM_John_Weeks]

Anil-

Whether you should go ahead or not would depend on the answers to questions you haven't asked. Primarily it will depend on the power amplifier being compatible with the 6221. You don't say what voltage range is required as input to the power amplifier, or the input impedance/current requirement for the power amplifier. You also don't address the question of the waveform frequency you require, though if this is a physical shaker (like sieve shaker?) it is unlikely to require a frequency higher than the 6221 can generate.

Any suggestions will also depend on whether you are writing your application in C/C++, or using Labview, or something else.

Good luck with your project!

[Anil_Reddy]

Hi John,

Thanks for your quick reply.

I am using LabVIEW for programming. 

This is a physical shaker. and i need 0-10V . Do we need to check any other thing?

waveform frequency range would be upto 4 KHz and i need continuos output waveform when i select Sine wavefrom. or a sweepsine with some finite duration (for ex: 30 sec)

Thanks

Anil

[WM_John_Weeks]

The PCI-6221 can certainly do 0-10V, and it's unlikely that the power amplifier will overload the analog outputs.

You should be able to get 4 a 4 kHz waveform as long as you're not too greedy with the number of output points per cycle.

As for examples, I'm afraid I'm not a Labview user- I do all my DAQ programming in C++. Hopefully someone else will offer something. Probably you should start by looking at the various waveform generation examples. I know there are quite a few that ship with NI-DAQmx, and I think Labview makes it pretty easy to access them. You can probably use on of them as the start for your own application.

[johnfr]

I have used the same PCI 6221 M-series board to drive a UD electro-dynamic shaker. It is a 1000 lb force shaker driving a slip table. I am doing a random vibration control. I use one of the AO's to drive the amp with a random white noise signal. (Every shaker amp I have worked with has a high input impedance that the AO should have no problem driving.) It has a closed loop control that shapes the spectral content of the white noise to compensate for the resonances in the shaker/slip table.  The biggest problem I have is the limited buffer size of the PCI 6221. I store 2 seconds worth of random data in the buffer and use auto refresh to update the buffer. Because it is random data there is a discontinuity between the beginning analog value and the ending value. This results is a tick occuring in the shaker every two seconds.   With a swept sine drive you will need to fill your buffer with a sine waveform that starts and ends at the same analog value (exactly 360 degrees electrical) and use a varying frequency clock to generate the sweep. In another earlier post about swept sine, the responder suggested using the second AO to drive the first AO reference to control amplitude which should work well. It may be possible to us a PID control to regulate the DC level of the second AO to control amplitude as the frequency passes through resonances in your shaker/load.