Detecting when a signal is stable

[carobin5]

Hi everyone,

I'm new to LabVIEW and am working on controlling a flow test. I'm sending the control valve a signal to tell it how much to open based on the desired flow rate. What I need is a way to recognize when the flow has stabilized and then take a pressure reading. I'm reading the flow rate in using a DAQ Assistant. My goal is to automate the test so that the user can type in what flow rates to go to and then LabVIEW does the rest. Any ideas? Thanks.

Oh and I just have the base version of LabVIEW.

[Ben]

The easy part is answering your question saying...

Monitor the standard deviation of a moving average and when it drops below a threshold the reading is stable.

The hard part will be deciding what that level should be particularly when you are calibrating over a wide range.

Ben

[aputman]

You could look at the last N readings and using a Pt.byPt. Std Dev VI, calculate the standard deviation of those readings.  If it is below a threshhold, you could assume that the readings have stabilized.  I don't know if the Pt.ByPt. VIs are available in the Base version. 

Edit:  Ben beat me to it.