topic Re: Temperature against time in LabVIEW

Temperature against time

ehalpin13 — Fri, 12 Jul 2019 09:42:47 GMT

Hi, I'm working on measuring temperature against time in labview (of a thermistor). The data comes in as voltage and gets converted to temperature in the subvi. I'm not sure whether I should be using a waveform or XY graph for this. I've attached the block diagram and subvi.

Thanks!

Re: Temperature against time

GerdW — Fri, 12 Jul 2019 11:20:01 GMT

Hi ehalpin,

I'm not sure whether I should be using a waveform or XY graph for this.

You should be sure about your requirements!

So what exactly do you want to display?

Waveform graphs are perfect for evenly-sampled data (fixed dt), while XY graphs are nice for data with random X coordinates. (You might also use waveform graphs for non-evenly spaced data when using the waveform datatype…)

Why do you need 2 local variables just to display data in the waveform graph?

Re: Temperature against time

ehalpin13 — Fri, 12 Jul 2019 11:26:15 GMT

Hi, thanks for the reply. I need to log a change in temperature over time so the waveform seems like the best option then!

Local variables were left over from something else I had tried out. Would it be better to just remove those?

Re: Temperature against time

crossrulz — Fri, 12 Jul 2019 11:35:47 GMT

@ehalpin13 wrote:

Local variables were left over from something else I had tried out. Would it be better to just remove those?

YES!

@ehalpin13 wrote:

Hi, thanks for the reply. I need to log a change in temperature over time so the waveform seems like the best option then!

You might want to consider moving the DAQ reading/logging into a parallel loop so it is constantly running and gathering data. You could change your graph into a chart then and make things simpler. You should also make sure your DAQ is set to be continuously running at a set rate (DAQmx Timing VI).

Re: Temperature against time

pallen — Fri, 12 Jul 2019 11:59:57 GMT

If you're looking to add a data points to "waveform" over time, it sounds like job for a Chart.

There's an article here on the difference between Graphs and Charts in LabVIEW.

Re: Temperature against time

RTSLVU — Fri, 12 Jul 2019 16:11:11 GMT

I use X-Y charts 99% of the time even though they are a bit more cumbersome, I like having complete control over how the data is presented.