saving and plotting acquired data

[Robbo13]

I've fixed the problem, which was mainly due to confusion with the differences between wiring single ended and differential inputs. I'm now able to record 3 channels of data simultaneously. I can then import this into my main program, format it and view on pretty nicely on graphs so I'm very happy!

The only thing I would like to improve is the formatting of acceleration values. At the moment our accelerometer isn't giving a zero voltage output while at rest, rather it outputs around 0.635 volts. When plotting the graph the output then varies + or - 2.5 volts from this value. At the moment I'm just subtracting 0.635 volts from the recorded values before they are plotted, but I wondered if there is a neater way to go about forcing the results to zero?

I might have to incorporate some signal conditioning to clean up the results somewhat, but I'm sure there are good signal conditioning examples which I can work from.

Finally our PDA arrived today so I can get on with trying to port the program to run on that, and hopefully we can get a testing session organised to allow us to obtain some proper results!

[smercurio_fc]

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Robbo13 wrote:

At the moment our accelerometer isn't giving a zero voltage output while at rest, rather it outputs around 0.635 volts. When plotting the graph the output then varies + or - 2.5 volts from this value.

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Is the 0.635V there when measured with a DMM, or only when you measure it using your DAQ? If it's there with a DMM, then it sounds like your device is not really giving 0V at rest, and I would check the sensor's documentation. If it's there when you measure it using your DAQ system, then you clearly have an offset voltage someplace. I would check the documentation for the specific DAQ device that you're using, as the docs typically cover these situations. 

[Robbo13]

I've just discovered that the PDA toolkit dosn't support the use of .tdms files. This is really irritating as i've already got my 2 programs set up to record then extract data from the relevnt channels within a tdms file. What alterative type of file can I use, does it have to be a binary file? And if so how do I go about extracting 4 separate channels of data from a binary file? 

[smercurio_fc]

As I indicated, I don't have the PDA Toolkit, so I have no idea what file formats are supported. Saving as binary is an option. The downside is that you won't be able to read out signals by name. This may not matter in your case, though. You can save the arrays of data directly to binary and read them in the same way. Check the examples that ship with LabVIEW. They show you how to read/write binary files.