Could not find examples for ni 9233

[sergueiK]

Where can I find code examples for NI9233 and NI9263 installes into cDAQ9172?

I have got Developer Suite with LabView8.5.

I have tried to use NI 9233 from LabView Signal Express as a signal generator and have found that there are actually 2 signals one of desired frequency (13 Hz) and some higher frequency maybe  about 100 Hz. So my oscillator moves not uniformly at 13 Hz but more like it is driven by stepper motor. I did not have this sort of motion when I was using hardware signal generator.

Thanks.

[Tom O]

Hi SergueiK,

The 9233 and the 9263 are compatible with DAQmx when used with CompactDAQ. To find useful examples for these devices, have a look in the LabVIEW example finder under Hardware Input and Output»DAQmx. The sub-categories that will be of particular interest to you are Analogue Generation and Analogue Measurements. These generic DAQmx examples are applicable to any of our multifunction DAQ devices, including your C-series modules when placed in a CompactDAQ chassis.

I'm not too clear on the issues you mentioned in the second part of your post. Am I right in saying that you see your 13Hz signal as desired with 100Hz of noise on it? Perhaps you could include a screenshot of what you see, and what you would expect to see? Unexpected noise on the signal is likely to be as a result of your experimental setup, consider possible sources of noise bearing in mind the frequency in question, and consider shielding cables etc.

Hope this helps,

[sergueiK]

Thanks Tom,

I already found examples, that work for me.

I have found that one way to eliminate this combined frequency response is to increase sampling rate and frequency.

I am not 100 % sure that this is the optimal way.

I will try to describe what I am doing in my application:

I have electro-mechanical vibrator powered by amplifier.

I feed amplifier from signal generator(in that case from NI9263) and read signal from accelerometer(through NI 9233).

I need to stabilyze amplitude of vibrations as there is some drift with time.

I have used exmples I found to create VI.

Could you, please take a look and give some comments on it.

Currently I am stuck on this close loop control.

I would like to stabilize amplitude within 1%. What is the best way to do it?

Message Edited by sergueiK on 03-12-2008 10:35 AM

[Tom O]

Hi SergueiK,

As a starting point for a contol application of this kind, you could have a look at some of the DAQmx examples for control. These can be found under Hardware input and output»DAQmx»Control»General. They show how to structure such programs, as well as how to apply control alogrithms to your application.

For your program, I would start by putting the acquisition and the generation the same loop. This way, you will acquire data, process it (perform spectral analysis and apply control techniques) and use that to control the output in each iteration of the loop. The specifics will depend on exactly how you wish to implement your control system, but with this approach you should be able to get some reasonable results.

Bear in mind that running with software-timed loops and control techniques from a Windows-based PC will never give completely reliable, fast and accurate control systems. For this kind of work, you may need to look into realtime processing.

Hope this helps, post back with any questions!

Regards,

[sergueiK]

Thanks Tom for the comments.

I realize that for reliable results I need to use real time module system.

I suppose that it would be not very difficult to move from my current configuration to real time one in a future(based on same modules but with with different interface base) using the codes I have prepared. Am I right? For now it is all laboratory use only so there is no need to have it bulletproof.

I have tried to place the acquisition and the generation into the same loop but as soon as I do this it just stops to work. I do not know what causes it and as I can not figure out it by myself I just leave it as it is with two while loops.

I have changed code a bit and now it has all I need(even a close loop control). Probably it all is not done in the best manner but any comments would be welcome.

[Tom O]

Hi SerguiK,

Whilst I can't check on the actual control algorithms you're using without knowing more about your system, the code itself should be OK. Both your loops are iterating once per second which means that the control should work fine. I would be tempted to increase the iteration rates on the loops up from 1 second to improve the response of your control system, but again this depends on your system.

Good luck with it for the future!

Regards,