{"id":7855,"date":"2016-10-07T09:00:08","date_gmt":"2016-10-07T13:00:08","guid":{"rendered":"https:\/\/blogs.mathworks.com\/pick\/?p=7855"},"modified":"2017-08-27T19:50:20","modified_gmt":"2017-08-27T23:50:20","slug":"data-acquisition-tool","status":"publish","type":"post","link":"https:\/\/blogs.mathworks.com\/pick\/2016\/10\/07\/data-acquisition-tool\/","title":{"rendered":"Data Acquisition Tool"},"content":{"rendered":"
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Sean<\/a>'s pick this week is Data Acquisition Tool<\/a> by Isaac Noh<\/a>.\r\n <\/p>\r\n <\/introduction>\r\n\r\n

Data Acquisition Hardware<\/a><\/h3>\r\n

Have you ever wanted to bring data directly from hardware into MATLAB or control something via a data acquisition board?<\/p>\r\n

Working with data acquisition hardware was my very first project in MATLAB back in the winter of 2008. I had a miniature\r\n load frame, transparent to x-rays, for applying a load to a concrete cylinder. There were three sensor inputs: two displacements,\r\n and force, and one output: a voltage to a piezoelectric actuator that applied a force. Here's a figure from my thesis:\r\n <\/p>\r\n

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I built a user interface in GUIDE to allow me to apply the load while recording and plotting the signals. To complicate matters,\r\n the session based interface for the Data Acquisition Toolbox<\/a> didn't exist yet, so I was also doing everything with timers on my own.\r\n <\/p>\r\n

I can only imagine how much easier it would've been with this app. I no longer have access to the load frame, so instead\r\n here's an example getting data from an ADALM1000<\/a>, a low cost data acquisition device.\r\n <\/p>\r\n

Let's control it with the app. First, I'll just get connected and pull some data from the attached RC circuit. Note I previously\r\n had to install the hardware support package<\/a> for this board.\r\n <\/p>\r\n

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Seems to work, great!<\/p>\r\n

Now I want to output some data to it. There are two channels, the first will be a sine wave and the second a cosine wave.\r\n The board can take 0-5V so add 1 to the waves keep them positive.\r\n <\/p>

t = linspace(0,8*pi,100000)';\r\nx = [sin(t) cos(t)]+1; %<\/span><\/pre>
In order to get them into the output, we simply pick the variable:<\/p>\r\n   
 <\/p>\r\n   
And then run the session:<\/p>\r\n   
 <\/p>\r\n   
From here, the data can be exported or equivalent code can be generated from the file menu to automate this acquisition session.<\/p>\r\n   
 <\/p>\r\n   
My only point of feedback is that error messages are not all exposed via dialogs.  For example, the first time I selected\r\n      x<\/i> with the range -1:1, it errored at the command line with a useful message that I didn't see because the app was maximized.\r\n   <\/p>\r\n   
Going back to my use case in college, I was trying to control load, with displacement so that the loading rate would be roughly\r\n      linear.  To do this, I ran a bunch of experiments and fit an equation to the load v. displacement curve for many cylinders.\r\n       At the time, I knew nothing about Simulink<\/a> or how it could help me.  If challenged with the same task today, I would likely use the data acquisition blocks<\/a> in Simulink R2016b to control the actuator. This would allow me to then use the PID block and its tuning capabilities to\r\n      accomplish what I was doing much more quickly.\r\n   <\/p>\r\n   
For nostalgia's sake, I put together a quick a model of the system.<\/p>\r\n   
 <\/p>\r\n   
Comments<\/a><\/h3>\r\n   
Do you work with data acquisition hardware?  Give it a try and let us know what you think here<\/a> or leave a comment<\/a> for Isaac.\r\n   <\/p>