Logging data from a LabJack T7 on a Mac

LabJack is one of the friendlier DAQ vendors for Mac users. Their LJM library, which every T-series device uses, has separate installers for Intel and Apple Silicon Macs, so it runs natively on current hardware with no virtual machine involved.

Once LJM is installed there are two good ways to log data from a T4, T7 or T8.

Option 1: A short Python script

LabJack publishes Python bindings for LJM. Install them with pip install labjack-ljm, then stream a few analog inputs to a CSV file:

from labjack import ljm
import csv, time

handle = ljm.openS("T7", "ANY", "ANY")
names = ["AIN0", "AIN1"]
addresses, _ = ljm.namesToAddresses(len(names), names)
rate = ljm.eStreamStart(handle, 1000, len(names), addresses, 1000.0)

with open("run.csv", "w", newline="") as f:
    out = csv.writer(f)
    out.writerow(["t"] + names)
    t, dt = 0.0, 1.0 / rate
    try:
        for _ in range(60):  # about a minute at 1 kS/s
            data, _, _ = ljm.eStreamRead(handle)
            for i in range(0, len(data), len(names)):
                out.writerow([round(t, 6)] + data[i:i + len(names)])
                t += dt
    finally:
        ljm.eStreamStop(handle)
        ljm.close(handle)

This is the right tool when acquisition belongs inside your own code. Stream mode matters here: reading channels one at a time in a loop tops out at a few hundred samples per second, while stream mode lets the device pace the samples and hands you blocks of data.

What the script doesn’t give you is everything around the data: a live view while it runs, triggers, alarms, a safe file if the cable drops, and a way to line the T7 up with the thermocouple module and the scope on the same bench.

Option 2: Record it in DAQAtlas (in development)

DAQAtlas, currently in development, loads LJM at runtime. With LJM installed, open DAQAtlas and the T4, T7 or T8 appears in the device list. Pick the AIN channels, set a rate and press Run.

• Live strip charts, scope, spectrum and readouts while you set up the test.
• Triggered recording: start when a channel crosses a level, keep a pre-trigger buffer, stop after a set time.
• Math channels and alarms evaluated on every sample.
• Export to CSV, MATLAB, TDMS, Parquet or HDF5 when you are done.

The bigger win is mixing hardware. If the T7 is reading vibration while an MCC USB-TC reads temperature and an Analog Discovery watches a supply rail, DAQAtlas records all three into one run, with shared markers, so you can review them together instead of aligning three files by hand. More on that in running a mixed-vendor DAQ bench.

Troubleshooting on macOS

• If the device doesn’t appear, make sure no other program has it open. Only one process can talk to a T-series device over USB at a time.
• Install the LJM build that matches your Mac: the arm64 installer for Apple Silicon, x64 for Intel.
• Over Ethernet or WiFi, the Mac and the T7 need to be on the same subnet, or you open the device by IP address.

Want to try it with your own T-series hardware? Join the DAQAtlas beta.