DAQ notes
Guides to running MCC, LabJack, Digilent and NI hardware on macOS and Linux, comparisons of DAQ hardware and software, and measurement fundamentals with worked numbers.
Comparisons and buying guides
Choosing the best USB DAQ under $1,000
LabJack, MCC, NI and Digilent sell USB DAQ devices from the $204 MCC USB-1208FS-Plus to the NI USB-6003 (from $928), and they differ most in input ranges and OS support.
6 min readDAQami alternatives for MCC hardware
TracerDAQ, DASYLab, DAQFactory, MATLAB, LabVIEW and Python can all log Measurement Computing devices, and of these only Python with uldaq runs on macOS or Linux.
7 min readData logging software compared
Of the nine DAQ loggers compared here, all but Digilent WaveForms and DAQAtlas (in development) are Windows only, and most are built to sell one vendor’s hardware.
6 min readLabVIEW alternatives for data acquisition
FlexLogger, DewesoftX, Python with nidaqmx and test platforms like Synnax can take over logging from LabVIEW, but deterministic control on CompactRIO or PXI still runs on LabVIEW Real-Time and FPGA.
7 min readCSV, MATLAB, TDMS, Parquet or HDF5?
CSV opens in every tool but stores numbers as text, while MATLAB .mat, TDMS, Parquet and HDF5 store binary data and differ in metadata and tool support.
7 min readDAQ on Mac, Linux and Python
Is there a DAQami for Mac?
DAQami, MCC’s free data logging app, only runs on Windows, but MCC’s open-source uldaq library supports Measurement Computing USB devices on macOS.
6 min readUsing NI DAQ hardware with a Mac
NI-DAQmx has no macOS support and NI-DAQmx Base stopped at macOS 10.14, so NI hardware reaches a Mac through Windows or a PC on the network.
6 min readLogging data from a LabJack T7 on a Mac
LabJack’s LJM library has native installers for Intel and Apple Silicon Macs, so a T4, T7 or T8 can log to disk from Python or a desktop app without a VM.
7 min readData logging with an Analog Discovery 3 on a Mac
WaveForms runs natively on Apple Silicon, and its Record mode streams an Analog Discovery 3 well past the 32,768-sample buffer, at up to about 5 MS/s total to disk.
6 min readHow to open a TDMS file on a Mac
NI’s Excel add-in and DIAdem are Windows only, but a browser viewer or the open-source npTDMS Python library reads .tdms files on macOS and Linux.
6 min readRunning MCC DAQ devices on Linux and a Raspberry Pi
MCC’s open-source uldaq library runs Measurement Computing USB and Ethernet DAQ devices on desktop Linux and Raspberry Pi OS, while the DAQ HATs on a Pi’s GPIO header need MCC’s separate daqhats library.
7 min readPython data acquisition across DAQ vendors
NI, LabJack, MCC and Digilent all ship official Python packages, but nidaqmx has no macOS support and mcculw runs only on Windows.
6 min readMeasurement fundamentals
How fast should you sample? Sample rate and aliasing
A 900 Hz tone sampled at 1 kS/s lands in your data as a clean 100 Hz sine, and no filtering after the fact can take it back out.
8 min readThermocouple measurement with a DAQ
A type K thermocouple produces about 40 µV per °C, so 1 mV of mains pickup on the leads is a 25 °C swing and a CJC sensor 1 °C off moves every reading by 1 °C.
9 min readMeasuring 4–20 mA sensors with a DAQ
A 0.1% 250 Ω shunt turns a 4–20 mA loop into 1–5 V on any voltage-input DAQ, provided the input range still shows the 21 mA fault level.
7 min readSingle-ended vs differential inputs
A grounded source measured in RSE mode closes a ground loop, and a floating source on a differential input drifts to a rail unless it has a bias resistor.
6 min readADC resolution vs accuracy
The 24-bit NI-9239 steps in about 1.25 µV, yet its typical accuracy at a 10 V reading is about ±3.8 mV.
7 min readHardware-timed vs software-timed sampling
With 100 µs RMS of timing jitter, software-timed sampling limits a 1 kHz signal to about 4 dB SNR, while a hardware pacer keeps sample spacing within its timebase’s ppm rating.
6 min readHow to synchronize multiple DAQ devices
Two DAQ devices rated ±50 ppm can drift 0.36 s apart in an hour, and a shared trigger, a shared clock or a marker signal each removes a different part of that error.
6 min readRunning a mixed-vendor DAQ bench
DAQ devices from different vendors run on their own crystals and write their own file formats, so lining up one run starts with a shared wall-clock start time.
7 min read