best AO device for continuous loop feedback

[FilipTTI]

Hi,

I want to apply  4 DC voltages in a feedback system. I am thinking of creating a loop, in which the amplitude of the 4 voltages is set/changed in each run of the loop. 

I wonder how much time it takes for each cycle to complete, I mean the time between setting the new values of the 4 voltages and that they appear on the output.

For the PCI-6703 (static output) device I find 0.9 ms in the manual - but I am not sure this value is what I think it is.

For the PCI-6711 device, I am not sure if you can apply DC voltages and change the amplitude at command, and I have no idea of the speed of changing the DC amplitude.

Can you suggest the best device for my application, and the time to change the DC amplitude at the output ?

Thanks,

Filip

[demux]

Hello Filip,

Which card is best suited for you really depends on what you want to accomplish and especially when you have the new desired output value available.

The PCI-6703 is a static output device to which you can 'write' a value that you want the AO to output. This is completely software timed. How fast you can update your signal varies with the accuracy you want to attain. You can find the settling times on page A-2 HERE

The PCI-6711 however is hardware timed and offers performance similar to an arbitrary waveform generator. The output of this one can update at a rate of 1MS/s on each channel. The principle is that you build an array of numbers that will be streamed to the card and the card will output. If you change these numbers, your card will output the new values. If you choose to build an array that contains the same number every time, you will be outputting DC.

Both cards are very capable in the field they were designed for.
I strongly suggest that you contact NI and explain your setup to the person responsible for sales in your region. He will help you make the best choice for your application.

You can contact NI at:

National Instruments Belgium NV/SA
Ikaroslaan 13
B-1930 Zaventem
Tel. +32 (0)2 757 00 20

Kind regards,
Wouter Van Hoof
AE Teamleader
NI Belgium

[FilipTTI]

Hi,

I purchased the PCI-6713 analog output card. I tested some Labview examples for continuous wave generating and so on. In the example "function generator.vi" I can output for instance a square wave and change the amplitude on the front panel. I am very surprised however that there is a delay of about 6 seconds between a change on the front panel and the actual corresponding change of the analog output, which is of coarse much to slow to use in fast PID systems as is claimed in the brochure of the PCI-6713 card.

My question is how can I use the PCI-6713 card to continuously generate for instance a square wave, and change the amplitude in each cycle of the loop (corresponding to one period of the square wave) in less than -lets say- 10ms? (or at least in less than 6 seconds) ?

Kind regards,

Filip