speed measurement using Labjacku3

2 posts / 0 new

Tue, 03/15/2016 - 00:38

santhosh

Hello,

I am using labjackU3 HV and labview for my motor. i need measure speed of motor after every 12 pulses. please give how to read in labview.

already with 1 pulse i am reading using frequency measurement block.

Please give me reply it is very urgent.

Tue, 03/15/2016 - 08:35

LabJack Support

So it sounds like you want to

So it sounds like you want to count pulses, and you want to know the time between every 12th pulse. For something like that I would consider streaming a hardware counter.

1. Configure the counter. Go to "config defaults" in LJControlPanel and enable Counter0. Click "Write Values", exit LJCP, and power-cycle the U3 so the new defaults are in effect.

2. Read the counter. Now you can go to LJStreamUD and read Counter0 using channels 210 & 224:

https://labjack.com/support/software/applications/ljstreamud

https://labjack.com/support/datasheets/u3/operation/stream-mode/digital-...

See the scaling equations page for more information about handling the 2 16-bit values you get from 210 & 224:

https://labjack.com/support/software/applications/ljlogud/ljlogstream-sc...

Set the first row to 210 and the second row to 224, and set #Channels=2. If you set scan rate to 10000 and click "Start Stream" you will get readings every 100us, so you know the time between any 2 scans in the data set.

Do the above with LJStreamUD to confirm this approach works. Then to do this yourself in LabVIEW you can skip step 1 above because you can do the configuration in your LabVIEW program. See the example "U3 Stream AIN with Timers & Counters.vi" to get started.

See the following for general information about frequency measurement:

http://forums.labjack.com/index.php?showtopic=1105