Troubleshooting#

Common problems and their solutions, organized by what you see.

Connection Issues#

Check that both the power cable and USB cable are securely connected.
Try a different USB port on your computer (preferably USB 2.0 or higher, directly on the machine — not through a hub).
Restart the NMR device, wait 10 seconds, then restart TQT Nuclei.
On Windows, open Device Manager and check for unknown devices under "Ports (COM & LPT)". If the device appears with a warning icon, reinstall the USB driver.
On macOS, check System Information → USB to verify the device is recognized by the OS.

Make sure Fake Mode is turned off in the HOME page connection panel. Fake Mode simulates a device and disables real hardware connections.

A red signal means either overheating or a sensor error:

Power off the device immediately.
Check that the device is in a well-ventilated area, away from direct sunlight or heat sources.
Wait 15 minutes, then power on again.
If the red indicator persists, the temperature sensor may need service — contact support.

Normal warm-up takes 1-2 hours. In cold environments (below 15°C), it can take longer.
Make sure the device is not near air conditioning vents or open windows — drafts cause temperature fluctuations.
If T_cur oscillates around T_set without settling, the PID controller may need adjustment — contact support.

Check frequency tuning. An incorrect frequency is the most common cause. Run HOME → FREQUENCY auto-tune or press AUTO TUNE.
Check the sample. Make sure the sample tube is properly inserted and contains enough material (at least 1 cm of liquid above the coil center).
Check pulse durations. If p90 is wildly wrong, you may get zero signal. Re-run HOME → DURATION tuning.
Check the receiver gain. If RX Gain is too low, the signal may be below the noise floor. Try increasing it in SETTINGS → Device.

Increase the number of scans — signal-to-noise ratio improves with the square root of the number of scans. Doubling scans gives ~40% better SNR.
Enable phase cycling — this cancels certain systematic artifacts. Set Num Scans to a multiple of 4.
Check dead time — if it's too short, hardware ringing contaminates the signal. Re-tune in HOME → DEAD TIME.
Check temperature stability — measurements during warm-up (yellow indicator) will have poor reproducibility.

Run auto-baseline correction in SETTINGS → Advanced → Processing.
Check that the phase is properly tuned — a misaligned phase creates a sloping baseline. Re-tune in HOME → PHASE.
If the drift is periodic, check for nearby sources of electromagnetic interference (motors, transformers, fluorescent lights).

Compare with literature values for your sample. Water at 25°C: T1 ≈ 2.5 s, T2 ≈ 2.5 s. If you're off by more than 20%, something needs adjustment.
Check the repetition delay — it should be at least 5× T1. If it's too short, T1 will appear shorter than it really is.
Check the echo time (for T2) — a very long echo time can cause signal loss before the first echo, biasing T2 downward.
Verify the fit — check the R² value. Below 0.95 suggests the fitting model may not match the data (try multi-exponential instead of single-exponential).

Re-tune p180 pulse duration — an inaccurate 180° pulse produces incomplete refocusing.
Check echo time — if τ is too short, pulses may overlap with the dead time.
Reduce decimation to capture more echoes and diagnose where the train breaks down.

Make sure your sequence ends with an ADC() node/call — without it, no data is acquired.
Check the Sequence preview graph at the top of the page to verify the timing looks correct.
Ensure seq_null is set correctly — it should be the total time before the first ADC window.

Verify the file has a .tl extension and hasn't been renamed or corrupted during download.
Check that your license hasn't expired — trial licenses are valid for 14 days.
If you recently reinstalled the OS, the machine ID may have changed. Contact support for a license reset.

Delete the application cache: on Windows, remove %APPDATA%/TQT Nuclei/; on macOS, remove ~/Library/Application Support/TQT Nuclei/.
Update to the latest version from terraquant.tech.
If the crash persists, check the log file (accessible from the status bar at the bottom of the main window) and include it when contacting support.

Close other resource-heavy applications.
Large experiment files (>100 MB) can slow down the Data Browser — consider archiving old projects.
On macOS, ensure TQT Nuclei has been granted necessary permissions in System Preferences → Security & Privacy.