Charting Function for V2.0?

[OKors]

Total Newb here,

I'm looking for some sort of "Charting" function in SignalExpress 2.0.

I'm using an SCXI-1000 with a 1520 bridge board. I'd like to display real-time historical data over say, 60 seconds. I was told by our field rep months ago that a charting feature was being built in natively in V_2.0. Before that I had a seperate VI written for charting that worked okay but lacked any configuration controls.

Thanks

[OKors]

Is there no edit option for this message board?

I think the term I'm looking for is Strip Chart. Basically I want my data to scroll across the graph along a time-based axis.

Hope this is making sense, please ask questions if I'm being confusing.

Thanks

[Phil_J1]

Hi,

Are you trying to chart waveforms or simple samples (scalars)? This option does exist for scalar values and you can configure the size of the buffer (number of samples shown in the chart history) in the Tools >> Options... menu, under "Data View >> Chart History Length" in that Options dialog, the default is 512 samples.

There is currently no way to do this for waveforms, but this is something we are looking to add in a future release.

Phil

[OKors]

I'm trying to chart samples (I think).

Let me explain a typical test setup in our lab:

All our testing is servo-hydraulically controlled (IE we use a digital output from a controller to control a hydraulic actuator). Inside the actuator is a built in LVDT, we'll also connect a load cell to the actator to measure force. 70% of our testing is Load vs. Displacement, but sometimes we measure strain vs. load, strain vs. displacement or all three (10-20 samples per second is typical).

Last week we did an Ultimate Falure test on a new bracket design, two channels, load and displacement. We start off at zero load and slowly ramp up the load till the bracket fails. On the DAQ software I can set up my graph to display Y vs. T or Y vs. X, either way when I start recording the data "line" starts at the left hand side of the graph and scrolls across the display in real-time like an old X-Y pen plotter.

I guess I'm not familiar with the term "scalars". I've seen it thrown around in the Help Menu but didn't know what it was. Does it have to do with the type of input your using? IE a thermocouple input would be a scalar input? And if so is the Charting function only available to those types of inputs?

Thanks for the help

[Matthew_W]

Hi CabShake,

It sounds like you would like SignalExpress to show data as it is acquired to the main data view. SignalExpress functions by displaying data by groups of samples, the Samples to Read in fact. What this means is if I configure SignalExpress to Acquire 10 samples at a rate of 1 Sample/Second then it will take 10 seconds to acquire this data.
 
   Total Sampling Time = Number of Samples to Acquire / Sampling Rate
                                      =  10 samples / 1 samples / sec = 10 sec

So, try the following experiment and prove this to yourself:

  1. Create a new project.
  2. Add a step: Acquire Signals->DAQmx Acquire->Analog Input->Voltage
  3. Hold Ctrl and select several analog input channels for display
  4. Click Ok
  5. Configure the Acquisition Mode as Continous
  6. Configure the Samples to Read as 10, the Rate as 1 hz.
  7. Run the project
  8. Observe how the graph updates.
  9. Now increase the rate to 10 samples/sec, now the graph will update all 10 samples in 1 second.

If the total time to acquire the group of samples exceeds 10 seconds then you will need to change the default timeout, this is done in the
 advanced timing Tab.

Please post back if this isn't sufficient to answer your question of how to display data at a realtime rate on the graph in SignalExpress.

Scalars: real numbers. Whereas a waveform would have t0, dt and scalar values attached to it.

Best regards,

MatthewW
Applications Engineer
National Instruments