Continuous data capture, single point logging

[Bandit]

Hi,

I want to execute a seemingly simple task in Signal Express, but can't find how to do it. I should add that I have only a little experience in Signal Express.

I wish to view some acquired data in real time (which I am succesfully doing) but only log a single instance when I judge the conditions to be right and I press a key or otherwise manually trigger the system.

So far all the options I have found dictate continuous logging.

I'm using Signal Express version 3.0.

Any help would be greatfully appreciated.

Bandit.

[Bandit]

Almost sorted. 

1. Adding a software trigger in the recording options tab start conditions will start the logging, and setting "repeat start stop cycle" to 99999999 times ensures I can do this as many times as I wish without the data acquisition being brought to a halt.

2. Setting the stop conditions to 1 second I found I had logged two sets of data - I'm acquiring at 1 per second. But setting the stop conditions to the same software trigger as I'm using for the start conditions ensures I have just one data set recorded.

3. I had missed the fact that you get a button for the software trigger on the interface!

BUT - the signals are logged out of order - instead of the order they are aquired in (1,2,3) they are always logged as (2,3,1). Very frustrating, I can't yet find the cause of this.

Bandit

[ShalimarA]

Hi Bandit,

Can you clarify some things for me. What type of measurement are you taking? Is it voltage, temperature etc? Also, when you say you're taking multiple samples, do you mean one type of reading from 3 different channels?

Also, do you mean that the plot order is incorrect on a graph? 

[Bandit]

Hi ShalimarA, Thanks for your reply.

I'm taking voltage measurements on 3 channels at the moment, with a 10V range. Each channel is measured as RSE.

The DAQ hardware is a NI-USB 6221. Shortly the application will build to use all 16 channels (by the end of this week).

Chart plotting in the application looks as expected, but when I log to file (tdms while running, converting to txt on completion) the columns are not in order in the text file.

I acquire and process channels in the order AI1, AI2, AI4, but the columns in the log file are ordered AI2, AI1, AI4.

Column headers are correct with respect to the data below them, it's just that the columns are not ordered as expected.

Hope this helps, please post back if you want more.

Regards,

Bandit.

[ShalimarA]

Thanks for responding so quickly, this makes alot more sense.

Can I point you in the direction of an example? I've found one that seems to be doing something very similar to what you're trying to do. It's logging a continuous signal from 4 channels and logs the data continuously. 

I'm not sure if it's available in version 3 of SignalExpress but if you go to the example finder and under the Data Logging folder, called 'Logging Acquired Signal Group and Playback.seproj' (although all of those examples would help you out quite a bit). Have a look in there and if you can't find it or anything similar, let me know and I'll send it to you. 

[Bandit]

Hi ShalimarA. Thanks for the pointer to the example, it is available under SE 3.0 and I have investigated it.

As provided, once I change the data channels to link to my device, it works as I expect. Logged data is in columns in the order aquired...

ai0, ai1, ai2, ai3 

But as you know from earlier, I wish to continually monitor on screen, and just log a single data set when something of interest occurs.

So I amended start and stop conditions in the recording options window.

        Start on software trigger (A), repeat 9999 times, log to current log.

        Stop on software trigger (A).

Now I get the functionality I require, log only 1 data set when I manually click the button, but again the columns are out of order. This time they log in the order...

ai1, ai2, ai0, ai3 

Perhaps from these steps you can replicate the problem.

I think it's a problem with either

         The way I understand the software triggered logging.

         The actual Signal Express software triggered logging.

Regards,

Bandit.

[ShalimarA]

Do you mind attaching your project so I can have a look around it?

[Bandit]

Hi,

Sorry for the delay, I was out of the office yesterday.

Please find the project file attached.

Bandit.

[Bandit]

Also please find attached an example log file with columns of data in the wrong order.

Regards,

Bandit.

[ShalimarA]

Hi Bandit,

I don't have a USB6221 at hand but after simulating one using your code, I've found that it does pick up the signals in the right order. This may be the obvious suggestion, but have you tried removing all the channels and then readding them?