QtDMM 26.2

Just received a message from the maintainer of the QtDMM digital multimeter software project to announce that the QtDMM2 v 26.2 has just been released. It’s packed with quite a lot of interesting new stuff, with support for 222 multimeters, including dual scale meters such as my trusty Bryman BM869s. There are versions for GNU/Linux, MacOS, MS Windows as well as FreeBSD, And, as the header image for this article demonstrates, it integrates beautifully with QT6 and the KDE Plasma 6 Desktop too.

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QtDMM – feature list

This is a bulleted list of its main features, lifted straight from the project’s documentation. What comes after version 26.2 is listed separately at the end of this article.

At a glance

Readout and recording software for digital multimeters and other instruments with a PC interface.
Since 2001: started by Matthias Toussaint, continued by tuxmaster from 0.9.5, now at https://github.com/qtdmm/QtDMM.
26.1 (4 October 2026) was the first release since 0.9.8; 26.2 is at the release candidate stage (rc1 of 12 October).
Calendar versioning: YY.N (26.1, 26.2, …).
Qt 6, C++17, CMake.
License GPL-3.0-or-later; the symbol sets are LGPL-3.0-or-later (KDE Oxygen/Breeze).
Runs on GNU/Linux, Windows, macOS and FreeBSD.
User interface in English, German, Spanish, French and Polish.
Website and handbook: https://qtdmm.de.

Meters

222 models from 48 vendors over 34 protocols; 88 of them confirmed with QtDMM on real hardware. The others were added from datasheets and protocol descriptions and are marked in the list.
Vendors include: UNI-T, Voltcraft, Brymen, Fluke, Keysight/Agilent/HP, Siglent, APPA (and relatives such as BENNING, Sefram, ISO-TECH), Metex, MASTECH, PeakTech, Tenma, Victor, Velleman, Elma, Greenlee, Sanwa, Digitek, TekPower.
Not only multimeters:
- luxmeters (UNI-T UT382, Benetech GM1020);
- thermometers (UNI-T UT325 and relatives, MASTECH MS6514);
- CO2 meters;
- Victron devices (SmartShunt/BMV, SmartSolar/BlueSolar MPPT, Phoenix Inverter).
Bench meters with SCPI (Keysight, Agilent, HP, Siglent) through sigrok-cli.
Meter keys on screen for the UNI-T UT60BT, UT61B+/D+/E+ and UT161: SELECT, RANGE, HOLD, REL, MIN/MAX etc. press the meter’s keys.
Unknown meters: protocol and interface can be set freely (Manual settings). The device list’s “Chip” column helps to find an identical meter.
Meters that need a hardware modification first are marked in the list.

Connections

Serial (RS-232): USB-serial adapters and native UARTs. The control lines (DTR/RTS) for cables that draw their power from them are set automatically.
USB-HID cables:
- HE2325U/CH9325, CP2110, CH9329 (UNI-T UT-D09 in both revisions) and Brymen BU-86X;
- a cable is found again after replugging;
- on Linux a udev rule with stable device names (/dev/qtdmm/…).
Bluetooth LE (Linux, Windows):
- UNI-T UT60BT, UT61B+/D+/E+ with the UT-D07B adapter, UT161;
- Victron via its encrypted “Instant Readout” broadcasts.
Network: RFC 2217 (a serial port over the network).
- qtdmm-bridge: a small service, for example on a Raspberry Pi, that puts serial and USB-HID meters on the network.
- QtDMM finds the bridges by itself via mDNS.
sigrok-cli as a backend for everything libsigrok supports.
Connection watchdog with automatic reconnect.

Setting up devices

“Add device” assistant:
- It asks how the meter is connected and searches there: USB cables, Bluetooth, network bridges.
- Recognised meters are listed first.
- When a port may not be opened, it says why and what to do (e.g. the dialout group).
“My devices”:
- Your own meters with their connections, in a sidebar.
- A click switches the meter; the context menu entry “Open in a new window” opens it in a window of its own.
“Find device”: a saved device is recognised by its place (USB port, Bluetooth address).

Displays

Digital display in LCD style:
- annunciators AUTO, HOLD, AC/DC, AC+DC, diode, continuity etc.;
- bar graph, min/max;
- colour variants: classic, blue backlight, amber, high contrast, custom colours.
Analog meter:
- auto-ranging scale, min/max marks, red zone;
- centre-zero scale;
- unit on the dial.
Readings table: every value with time, function and range, plus min/max/mean/span. Copy to a spreadsheet or export.
Poincaré plot: each reading against the next. Noise and drift show at a glance, with SD1/SD2 and their ellipse.
Window layout:
- all views as windows in one area, arranged automatically or freely;
- workspaces saved to and loaded from a file.
Designs System, Silver and Dark.
Symbols: Oxygen in colour, Breeze light/dark, or the desktop’s icon theme.
A meter that falls silent shows at once: the displays fade its value.

Graph and recording

Three modes:
- Live: runs right after connecting;
- Recording: ● REC with elapsed time;
- View: a finished recording or an imported file.
Every reading is stored with its time:
- no fixed sampling grid, short spikes are not lost;
- up to two million readings per recording.
Start:
- by hand;
- at a clock time;
- when a threshold is crossed upwards or downwards, with pre-trigger: the recording reaches back by the time set before the trigger, a green mark shows it.
Length is asked at the start, or the recording runs until stopped.
Clean data:
- an overload (OL) or a dropout is a gap in the graph instead of a wrong value;
- when the meter switches to another function (V → Ω), the recording ends with a mark; a recording never mixes two quantities;
- a range change (mV → V) carries on.
Graph:
- time buttons All / 1 min / 5 min / 30 min; zoom with mouse wheel and keyboard;
- crosshair with time (ms) and value;
- vertical axis in the unit the meter shows (350 mV, not 0.35 V);
- long recordings stay fast without losing spikes (min/max per pixel column).
Integration curve: the integral over time, e.g. Ah or Wh from a current or a power.
Colour variants: neutral, scope blue, phosphor green/amber, chart recorder, custom colours.

Alarms

Named conditions:
- above, below, outside a range;
- overload;
- readings stop coming.
With a minimum duration and hysteresis.
Actions:
- banner, beep, popup, bring the window to the front;
- mark in the graph;
- start/stop a recording;
- run an external program with value and unit as parameters. If wanted, QtDMM releases the port meanwhile, so the program can use the meter itself.

Export, import, print

Data export:
- CSV, Excel (.xlsx) and OpenDocument (.ods), with real date and number cells;
- on the grid of an adjustable interval (time-weighted mean) or every single reading.
Import of CSV, also the format of old QtDMM versions.
Graph as an image:
- SVG and PDF as vector graphics, e.g. for Inkscape and documents;
- PNG and JPEG;
- as a picture to the clipboard.
Print with title and comment.

Several meters, calculated values

Several meters at once, one per window (instance).
Recording started and stopped in all instances in sync.
Calculated values: an instance computes a formula from the readings of the others, e.g. power = voltage × current. The result is shown, recorded and exported like a meter.
Simulated meter:
- waveforms sine, triangle, square, sawtooth, random, constant;
- plus noise and custom formulas;
- for trying QtDMM without hardware, for demos and testing.

Remote access

SCPI server:
- the meter answers like a lab instrument to *IDN?, READ?, CONF? etc.;
- raw TCP socket and HiSLIP (VISA);
- usable from lxi-tools, Python/PyVISA, NI-VISA and LabVIEW;
- announced on the network via mDNS.
Screenshot of the QtDMM window over SCPI (HCOPy:SDUMp:DATA?), as with a bench instrument.

Operation

Keyboard shortcuts for everything important (function keys for connect, settings, recording etc.).
Handbook built into the program (F1); the same pages are on qtdmm.de.
Command line: several configurations (--config-id); --debug prints every frame as hex (for bug reports).
Settings on six pages. The settings dialog neither disconnects the meter nor stops a recording.

Platforms and packages

Linux:
- AppImage as a ready-made download;
- DEB and RPM from the sources (./compile.sh pack), spec file for Fedora COPR;
- PKGBUILD for Arch/CachyOS;
- Nix flake (nix run github:qtdmm/QtDMM), on NixOS with the udev rule. The flake comes with 26.2.
Windows: installer and ZIP.
macOS: .dmg for macOS 13 and later. Bluetooth is not available there yet.
FreeBSD: build from the sources.
Release builds are made automatically from git tags; source archive with a fixed checksum for distributions.

For contributors

Protocols: every protocol is documented as a specification with test vectors (docs/protocols). The decoder tests are generated from them.
CI builds and tests for Linux, Windows, macOS, FreeBSD and Nix.
Doxygen API documentation online.
Contributions:
- CONTRIBUTING and issue forms for bugs, device reports and new meters.
- A capture with --debug and a note of what the display showed is enough for a new decoder.
Disclosed openly: an AI assistant (Claude) helps with the development.

After 26.2 (work in progress, not in this release)

This is what to expect in 26.3 and beyond…

Graph:
- reference line that snaps to 0, mean, min or max or to an alarm threshold;
- time cursors A/B with Δ, mean and integral, as flags below the graph;
- overview strip (minimap);
- min/max envelope.
New UNI-T Bluetooth meters:
- UT202BT clamp meter;
- UT383BT luxmeter;
- UT353BT sound level meter;
- UT363BT anemometer and UT333BT (temperature/humidity) to follow.
- They bring new units (m/s, %RH, dBA/dBC).
VXI-11 next to raw SCPI and HiSLIP.

A sneak preview of 26.3 and beyond can be seen by compiling from source, as detailed here.