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LJStreamM - Windows Only

LJStreamM is a simple ready-to-run executable that streams up to 16 input channels from a single device. It displays selected channels on a graph and writes data to file.  Generally used for >100 scans/second.

See the Communication section of the T-series Datasheet for background on streaming. Also see the Data Rates Appendix and the LJM library stream section.

Supported devices


The application LJStreamM is included with the main installation package.

For LabVIEW programmers, the source code is available in the LabVIEW_LJM archive.


It is recommended to initially just open and click Start Stream without changing any settings. If you have recently modified settings and are having problems, close the program and delete LJStreamM.cfg in your current working directory. Open again, select Use default Configuration in the experiment configuration selection window if using LJStreamM v1.07+, and you will have the default settings.  If you have problems related to opening the device, select Open First Available Device in the device configuration selection if using LJStreamM v1.07+ or delete LJStreamM_open.cfg and restart LJStreamM if using an older program version.  For problems related to the working directory location, see "Change Working Directory" below.

LJStream vs. LJLog: We suggest that you use LJLogM if possible, and only if you need to go too fast for LJLogM do you then switch to LJStreamM.  LJLogM uses command-response mode, so it acquires and processes 1 scan at a time at the specified interval and is generally used for ≤100 scans/second.  LJStreamM uses stream mode, so each iteration it retrieves and processes 1 seconds worth of scans and is generally used for >100 scans/second.  For more discussion of command-response mode and stream mode see Section 3 of the T7 datasheet.

LJStreamM vs. LJStreamUD:  LJStreamM supports the T-series.  LJStreamUD supports the U3, U6, and UE9.

Logging from Multiple Devices: It is possible to log from multiple devices at once by copying and renaming LJStreamM.exe then running both the original and copied LJStreamM applications. LJStreamM.exe can be found by pasting %HOMEDRIVE%\Program Files (x86)\LabJack\Applications in the Windows File Explorer address bar.

Logging for Multiple Experiments (v1.06 and earlier): LJStreamM loads configurations from the last working directory. To keep configurations for multiple experiments, you can copy config files (LJStreamM_open.cfg and LJStreamM.cfg) into the last working directory before opening LJStreamM. Alternately, you can create a folder for each experiment and put a renamed copy LJStreamM.exe in each of those folders. For example, you could use the following folder structure:


Then LJStreamM_force.exe and LJStreamM_temp.exe each keep their own working directory, with their own copy of config files and data files.

Logging for Multiple Experiments (v1.07+): LJStreamM v1.07 adds new configuration settings. When the program starts, a pop-up window will appear asking for a method to open a device. The Load Open Configs from a File selection is intended only for advanced use with custom open configuration files. See "Device Type & Address (Opening)".

Once the open configuration is selected, another window will appear asking for experiment configuration settings. By default, experiment configurations are saved to LJStreamM.cfg.  If default settings are selected and LJStreamM.cfg does not exist, default values will be loaded. 

When the program is closed, the selected experiment configuration file is written to the current working directory with the current experiment settings. For example, if  "Load Experiment Configuration" is selected in the experiment configuration window and a configuration file called MyExperiment.cfg is loaded,  a configuration file called MyExperiment.cfg will be written/overwritten in the current working directory when the program exits.

Experiment configuration files are not intended for direct editing. To make backup or alternate experiment settings see "Save Current Config" below.

Control Descriptions

# Channels: 1-16.

Scan Rate: Put in the desired scan rate.  Sample rate is scan rate times number of channels.  See Appendix A-1 of the T-Series Datasheet for more information on data rates.  ScansPerRead is hard coded as ScanRate/2, so this program will iterate about every 500 ms.

Range, ResolutionIndex, and Settling Time: To configure these analog input settings, close LJStreamM and use Kipling.

DevType, ConnType, &  SerialNumber (Opening):  These indicators display information about the device that has been opened.  To control what device is opened, edit the LJStreamM_open.cfg file that can be found in the working directory.  If you don't see it, make sure you have opened & closed LJStreamM at least once after installation.  Unlike LJStreamM.cfgLJStreamM_open.cfg is intended to be directly edited by the user.  This file has an intro line and then 3 lines to specify Device Type, Connection Type, and Identifier. The default values are ANY-ANY-ANY, meaning that LJStreamM will open the first device it can find.  For further information see the Device Opening section of the LJM User's Guide. Example open configuration file:





If the configuration file is ever rendered unusable, delete it then open and close the application so that it will make a new default configuration file.

This provides a way to run multiple instances at the same time talking to different devices.  Make a copy of LJStreamM.exe called LJStreamM2.exe, run LJStreamM2, set the working directly as desired, and close LJStreamM2.  Now edit both LJStreamM_open.cfg and LJStreamM2_open.cfg to specify the device for each to open.

Name: Specify the desired register Name for each row.  For example, the first row defaults to AIN0, but could be any streamable register such as  AIN9, EIO_STATE, or DIO2_EF_READ_A.  See Section 3.2 of the T7 Datasheet for a listing of streamable registers.  Any related configuration, such as AIN#_RANGE& STREAM_RESOLUTION_INDEX for analog inputs, needs to be done in Kipling before running LJStreamM.

Voltage: This array displays the raw value for each row.  Usually a voltage, but can be something else depending on the Name.  The displayed value is actually the average of all scans returned each iteration.  When not streaming, the value shown is from a command-response read.

Scaling Equations: Should be something like y=a, where y is the scaled output and a is the input voltage of the 1st row.  b through p would be the input voltage of the rest of the rows.  Everything after // is ignored, so use for comments.  A few examples:

y=c                                  // Scaled value equal to raw value from 3rd row
y=100*c                           // EI-1034/LM34 voltage to deg F
y=c-273.15                       // deg K to deg C
y=((c-273.15)*9/5)+32      // deg K to deg F
y=TCVoltsToTemp[K:c:a]    // Type K, t/c voltage from 3rd row, CJ temp from 1st row

For more details see the LJLog/Stream Scaling Equations page.

Save Current Config: Click this to save your current experiment configurations. Once clicked, a pop up window will appear asking for a file name and an OK button that will create the file once pressed. The resulting file will be saved to the current working directory with a .cfg file extension.

Write To File: Click this to start and stop writing to file.  The resulting file is a tab-delimited ASCII file.  The first column is elapsed time (in seconds) since you started writing to file (does not reset when a new file starts automatically due to Max File Size).  Files are written with a .dat extension.  To quickly open in Excel or Open Office Calc, change the extension to .xls or .ods.  To import to a Google Spreadsheet, make the extension .tsv before uploading.

Each row of logged data typically requires roughly 10 bytes for the timestamp plus roughly 10 bytes per channel.  So it you log 8 channels at 1000 scans/second for 60 seconds that would be about (10 + 10*8) * 1000 * 60 = 54000000 bytes on the hard drive.

Data File Prefix:  LJStreamM uses this as the base string when it makes a file name.  When LJStreamM starts a new file, it appends a "_#" to the specified prefix, where "#" is an unused number from 0-99999.

Max File Size (Bytes):  When the current data file exceeds this limit, it is closed and a new file is started.  In theory the max value is 2^31 - 1, or 2147483647, but we have not tried a file that big ourselves.

Change Working Directory:  Click this to select the directory where the config file and data files will be saved.  After navigating to the desired directory in the pop-up window, click Select Cur Dir at the bottom-right.  For more details see the LJLog/Stream Working Directory page.

Graph History: Controls how many scans are shown on the graph.

DisableScaling:  Scaling is computing intensive.  If LJMScanBacklog is growing, disable scaling.

Revision History

1.07: Added configuration selection and save settings.

1.06:  Fixed problem where time reported on the chart and in logged file was twice the actual time.  Added separate error message displays for C-R and stream modes.

1.05:  Set minimum value of #Channels to 1.  Fixed problem where name of the exe was not detected properly.  Fixed issue where you could never decrease the number of channels shown on graph.  Changed version check sub-vi so it only shows prompt when new version available ... not on version check errors.  Changed scaling sub-VIs to use LJM thermocouple function rather than LJUD function.

1.04:  Added support for SignedLSWMSW[lsw:msw] function in scaling equations to handle quadrature reads.  For efficiency, scaling equations now skipped if no scaling is needed (e.g. y=a).

1.03:  Changed all text to Segoe UI font so screen items are aligned regardless of system font size.

1.02:  Fixed problem with saving of configuration settings.

1.01: Changed to use this application's filename (w/o extension) to create the names of the config files and registry entry.  Added "Write To File" control to items saved in config file.

1.00: Initial version.

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