Display Strip Chart Recorder view in Signal Express

[skaterdad]

I wish to display a strip chart recording view of a slow speed signal (f=0.25 to 1.0hz) signal which represents position as translated through a resistive (1k) linear position tranducer (ie Unimeasure LX-PA series).  This display should shift leftwards as new signals are acquired, rather than updating the display one screen at a time like a scope; ie most recent signal is on the right side, and N seconds ago are displayed on the left edge.

I am a Signal-Express LE 'newbie'.  I've got the signal properly coming in from the NI USB 6211 and displaying like a scope, but can't figure out how to change the view to what I want.

Any thoughts or suggestions?

[OKors · Accepted solution]

You need to pass your signal through an Amplitudes and Levels step:

• Add Step>Analysis>Time-Domain Measurements> Amplitudes and Levels.
• Go into the Set Up settings and de-select RMS leaving only the DC value checked.
• From there just drag and drop that signal (the newly created DC signal) into the graph
• Right click on the chart and select Update Mode
• You should now have the option to view as Strip, Scope, or Sweep chart.

Hope that's what you're after!

[skaterdad]

That worked! 

One thing that I guess I stumbled on was this computer was using a 'demo' copy of SignalExpress, so I had to turn on the licenced features first...  That helped!

Thanks for your prompt help!

[OKors]

Keep in mind though, if you SAVE the actual DC signal from the Amplitudes and levels step your sample rate will not be the same as saving just the raw voltage signal straight from the DAQmx Acquire step.

By passing the signal through the A&L step it applies some 'smoothing' function or some kind of averaging.

In other words, if you save the raw voltage from the DAQmx Acquire step and set your Rate to 1khz and samples to read to 10 and take 1sec of data you will have a file with 1000 data points (the samples to read has more to do with how fast the samples get thrown up on the graph).

If you save the DC signal with the same settings (Rate=1k S2R=10) and take 1sec of data, you'll end up with a file with only 100 sample points.

The formula for this is Rate/Samples to Read= actual saved DC signal sample rate.

In most cases this may not matter but I run a lot of tests where the engineers have to know the actual sample rate and apply it to their models.

Someone else can probably explain that a little better but for now that's the layman's explanation...