Data Logging SCC-68

[carleethian]

How fast can I sample the DAQ.  I'm taking 4 analog inputs and writing them to an ASCII via LabView SignalExpress.

I keep getting buffer overflow errors saying that the sample period is too short.  I'm currently at 20ms.

How short can I make it?  It seems a bit ridiculous that this thing can't sample at <50Hz.

[Dennis_Knutson]

An SCC-68 cannot sample at all. It is just a dumb terminal block. What is the actual DAQ device you are using? Are you just using Signal Express or are you using LabVIEW? There is a dedicated forum for Signal Express if that is all that you are using. LabVIEW was used to create Signal Express but you probably won't find too many users of it here.

[carleethian]

Whoops, I reposted over there.  Thanks.

[carleethian]

I actually would like to make a version in LabView.  Is there an example anywhere for a data logger that can sample at a frequency ~100Hz?  Or at least anywhere near there?

I'm sampling at 10Hz in SignalExpress and am continuously crashing and resetting it.  There has to be an easier way.

Thanks for any help,

Colin

[Dennis_Knutson]

There are a lot of examples and unless you are using a software timed analog input card, they can all sample at frequencies much greater than 100 Hz. You still have not provided the actual model of DAQ card. Nor have you provided any information on how you are actually sampling now. You haven't done something such as requesting a single sample at a time, have you? That would force the code to switch to software sampling mode and greatly reduce the sample rate.

[carleethian]

I was trying to do continuous sampling, but the # of samples seemed to affect how much data I could take in.  It would look like it was sampling, but the timing would reset each time the buffer filled up, and each buffer had all of the exact same values in it.  Do you have to reset the buffer each time it fills up so that you can get continuous data?

In short, I am doing single sample acquisitions because I couldn't find another way to get a continuous data stream.

The DAQ card I have is the PCI-6229 with a SCC-68 attached to it.

Thanks for the quick reply,

Colin

[Dennis_Knutson]

This is when you were running signal express? If so, I have no experience with that but I am using the same DAQ card. I just created a task that does continuous sampling/Samples to Read = 250k, Rate=250k and have no problems or errors.

[carleethian]

Ok, I'm actually in LabVIEW now.  I have a DAQ Assistant outputting 4 analog signals to a Write to Measurement File which is creating a .lvm

It actually seems to be working now thanks to you. I thought the Continuous Sample option did something else, but it is working fine now, thanks.

One last thing, is there a way to get the time stamp to be in regular format?  I'm planning on comparing the data from this to another data log to look for a certain phenomenon going on.  Right now I'm just pressing go when the second hand on the computer gets to :00.

Thanks again for the help,

Colin

[Dennis_Knutson]

Define 'regular format'.

Note that Write to Measurement File is not something I would recomend modifying (at least for a beginner).