3.6 - LJstream [U12 Datasheet] | LabJack
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3.6 - LJstream [U12 Datasheet]

Uses stream mode to read, graph, and write to file, 4 AI channels. For more information, read about the stream functions (AIStreamStart, AIStreamRead, and AIStreamClear).

  • Enable Stream: Starts and stops the stream acquisition.
  • Scan Rate: Determines the scans/second (50 to 300).
  • Number of Scans: Determines the number of scans that will be collected each iteration, and thus determines how fast this application iterates.
  • Demo: Calls the “AIStream” functions in demo mode so timing and data is simulated.
  • Read Counter: Collects 1 analog input and the counter if selected.
  • Configure Channels: Click this button to bring up the channel configuration window shown in Figure 3.6-2.
  • Save Current Settings: Saves all the current settings, including channel configuration.
  • Graph History: Determines how much past history appears on the graph.

Figure 3.6-1. LJstream

Figure 3.6-2 shows the LJstream channel configuration window. Here you can select analog inputs and gains and enter scaling equations. Use “Test Data” to see the effect of the scaling equations (“v” column is the measured voltage and the “y” column is the output of the scaling equations). “Manual/Sampled” determines where the “Test Data” in the “v” column originates.

Figure 3.6-2. LJstream Channel Configuration


I am trying to record more than 14 channels of analogue data.  I have 2 UE9 labjacks. 

Can both be run simultaneously using the LJstreamUD software?  If so, how are they configured such that I can run the 2 ue9's simultaneously or at least run 2 parallel instances of LJstreamUD. 

Do you need to use stream mode?  There are complications to consider in how to synchronize stream data, so if you don't have to use stream mode I would use command/response mode.  See Section 3.0 of the UE9 User's Guide.

LJStreamUD and LJLogUD are both limited to 1 device.  You could use a Mux80 to get more channels from 1 device, but both of those apps are limited to 16 channels, so to do more channels you need a different software solution.

Is there any config file stored in windows when current setting are saved? If yes, where is it stored?

Yes, look for "ljstream.cfg" in the working directory.  If you are not sure what the working directory is, click "Enable Stream" and then click "Write To File" and see where the data file is written to.

stijn's picture

How do I read more than 4 AI channel with only 1 LabJack U12. If this is impossible LJStream, do I then need to use LabVIEW?

labjack support's picture

LJstream uses stream mode which is limited to 4 channels on the U12:



Try using LJlogger instead, or of course LabVIEW is an option if you want to make your own program.

stijn's picture

The sample time ( Data file write interval) is limited to 0.5second, is that correct? I need sampling times of like 10 ms.  Can I work arround this?

labjack support's picture

The U12 is not able to do that:


For the fastest speeds with >4 channels chck out LJsimplelog:


To go faster you will have to use any of our other devices, such as the U3: