Comments on: Advanced MATLAB: Data acquisition in MATLAB

By: dhull

dhull — Thu, 30 Jul 2009 13:26:04 +0000

@pirat,

You are best talking to htt://www.mathworks.com/support for this.

Thanks,
Doug

By: Pirat

Pirat — Thu, 30 Jul 2009 12:30:25 +0000

hi doug. i want to ask you about using data acquisition card to record data from an oscilloscope realtime and process it with Matlab. i’m able to use getdata, but it’s blocking since i want real time recording and processing, then i will write a GUI to calculate the period, amplitude and some other things.Thank you

By: Javier

Javier — Mon, 06 Jul 2009 13:43:50 +0000

i’d like to know how can i import data for a transducer of human pulses into matlab without help of other hardware. the sensor has a USB terminal?

By: Gamal

Gamal — Fri, 10 Oct 2008 19:12:15 +0000

Thank u Doug for ur fast reply. yes I have an NI-DAQ USB 6008. and I have an Analogue voltage sinusoidal signal that have a maximum frequency of 500KHz which means i want a minimum sampling of 1 Mhz. I want to analyze this signal using matlab( getting FFT) real time. can this be done by using the ADC in NI-DAQ or i have to get another ADC. if so how can i interface it with matlab. thanks alot Doug and I am waiting for your reply.
Gamal

By: Doug

Doug — Mon, 06 Oct 2008 13:19:28 +0000

Gamal,

That is something that can be done. Do you have the Data Acquisition toolbox? What have you tried, can you connect to the board? What board is it?

Doug

By: Gamal

Gamal — Sun, 05 Oct 2008 16:17:00 +0000

Dear Sir,
I am working in a project that i use an Analogue to digital converter HW to transfer analogue electrical data to digital. I want to read this digital these data via Matlab using USB port in order to get its FFT. I would be very glad if you tell me how to do that. thanks alot for your help.
Gamal

By: pierre

pierre — Thu, 28 Aug 2008 19:04:27 +0000

Hi sherryl and thank you for answering me,

Actually, I already tried before to use this property because I saw that it was what I wanted, nevertheless I got this error:

EDU>> AO = analogoutput(’ueidaq’,'pwrdaq://dev0′);
EDU>> addchannel (AO, 0);
EDU>> AO.OutOfDataMode = ‘DefaultValue’;
??? Error using ==> daqdevice.subsasgn at 108
Error using ==> daqdevice.set at 261
Invalid property: ‘OutOfDataMode’.

Then I tried to skip it just by doing :
EDU>> AO.Channel.DefaultChannelValue = 5;

And then I had no error but also no effect : I still got a value of “zero” instead of 5 volts between the two steps ..

I don’t know why this property is not recongnized, do you ?
I am using the R2007a student version of matlab.

Thanks,
pierre

By: Sherryl

Sherryl — Thu, 28 Aug 2008 18:10:39 +0000

In Response to Post #10 by Bryan -
Hi Bryan,
By default the analog input object will acquire one second worth of data.
There are many ways to acquire more than that.
1. Set TriggerRepeat to greater than 0
2. Set SamplesPerTrigger to a larger number than the default, which matches the default SampleRate
3. Use either a TimerFcn or SamplesAcquiredFcn callback to restart the acquisition

All of these things are well documented here:
http://www.mathworks.com/access/helpdesk/help/toolbox/daq/daq.html
They can also be seen in the demos . Bring up MATLAB and type:
demo(’toolbox’,'data acquisition’)
at the command line (requires that Data Acquisition Toolbox already is installed).

Regards,
Sherryl

By: Sherryl

Sherryl — Thu, 28 Aug 2008 18:05:12 +0000

Hello Pierre,

Please look at the OutOfDataMode property.
http://www.mathworks.com/access/helpdesk/help/toolbox/daq/outofdatamode.html
You can use it to set a value that will be held when the queued data has been output.

start will not set the output voltage to zero until that value is in your output signal.

Regards,
Sherryl

By: pierre

pierre — Thu, 28 Aug 2008 16:47:36 +0000

Hi all,
I have the Data Acquisition Toolbox, and I’m trying for 2 weeks to send a step voltage, and just after another one of a different voltage WITHOUT going back to “zero” between the two..
I tried to do it little by little and I saw that the “start” function between the two steps reinitialize the voltage at a value of zero volts. And I wouldn’t like it because the piezo I want to control has a really fast response time..

Furthermore I think I am compelled to use a “start” function between the two steps because I have to compute de Amplitude of the second step in real time so I don’t have to prepare the two steps before and put both of them in the engine using one “putdata”.

Is there a way to avoid it ?
Thank you a lot, This problem is really annoying me.

Pierre