Monitor the data change

[phyyu]

Hello guys,

I have a little problem here. I got the data stream from the data acquisition device, and the data could be indicated on a chart. I could see the waveform on the Labview front panel, and even got the data value from the indicator. However, I need to record the data at one moment, and record another data after a small time interval. Then, I need to monitor the data change.  Any good idea? Thank you!

[phyyu]

Thx!

[MarcoMauri]

If you want to record data at a given time maybe the waveform is not needed and you can switch to single point acquisition.

Can you givemore details about "monitor[ing] the data change"?

[phyyu]

Thank you for your reply.

I would like to monitor the data, when the data sudden drop-down, I could send a message to switch off the system. My idea is obtain a data at one moment and obtain another data after a small time interval. When the change is larger than acceptable value, I switch it off.

Could you show me more detail about single point acquisition? So appreciate!

[Paul-B]

Hello Phyuu,

What type of data change are you trying to monitor, a change in the time interval or a change in the voltage. You could keep track of the amount of time passed with an Elapsed Time Express VI.

[phyyu]

Hello Paul,

I try to monitor the change in the voltage. The data is in volts. My problem is, I could read these data from a numerical indicator instantaneously. However, I need to record a single data (voltage value) at one moment and another single data a few millisecond after, and compare these two data. Could that easily to reach? Thank you!!

[MarcoMauri]

I would suggest to give a look to the transition detection vis:

"Threshold Detector PtbyPt.vi" and

"Threshold Detector.vi"

Marco

[shjukheter]

I am guessing that you will get a chunk of data from DAQ and you can log this data continuously and see the Max and min value in that arrived data continuously. It may be the solution that you want.

See the VI's in array pallet.

Max and Min array VI and Sort 1D array VI.

[MarcoMauri]

Simply using min and max can give problems due to noise resulting in false alarms.

That's why I prefer using threshold detection functions.

Regards,

Marco