Build & Run an Experiment

An experiment module is one kind of measurement: a plan of steps that drives several instruments and records what they return, one folder per run (see Data Flow). This guide builds one from nothing: power-dependent photoluminescence (PL) of a quantum dot — a simpler version of the lab's plesty-pow-pl.

The excitation laser passes a half-wave plate on a rotation stage, then a fixed polariser, so turning the plate sets the power that reaches the sample. The plate turns from 0° to 180° in 2° steps. At every angle the spectrometer takes one spectrum, and the power meter reads the excitation power alongside it — so each spectrum carries the power it was measured at. That is 91 rows, then an analysis of the power against the angle.

1. Scaffold — plesty init experiment, and what it writes.
2. The Rig — the three instruments, reached by name.
3. Run Setup — which devices a run uses, and on which bench.
4. Plan & Steps — the plan, and what one row does.
5. Run & Resume — run it, stop it, continue it, read it back.
6. Analyze — fit the excitation power, and report the fit.
7. Watch It — the spectrum, the map and the power, live.
8. Test It — the contract gates, without hardware.
9. Run It from the Bench — the same module, run across lab PCs from PLESTY Bench.

What you need

• plesty-sdk for plesty init — uv tool install plesty-sdk.
• plesty-server, which installs and runs instrument servers from a terminal — uv tool install plesty-server.
• The three instruments, replaying a real measurement. The stage (plesty-k10cr1), the spectrometer (plesty-lightfield-spectrometer) and the power meter (plesty-pm100d) all run in --mock — but these mocks do not invent their answers: they replay a sweep really measured on 4 August 2026, which the demo/mock-replay branch of each module carries. The stage writes the angle it reached into a folder all three share, and the other two answer for that angle.

Save this as fleet.yaml in an empty folder — a fleet is the list of instrument servers one PC runs:

version: 1
home: ~/.plesty/tutorial              # where the servers are installed, apart from any bench of yours
devices:
  pm100d:
    package: plesty-pm100d
    git: https://gitlab.com/plesty/hub/devices/thorlab/plesty-pm100d.git
    ref: demo/mock-replay
    args: [--mock]
    env: {PLESTY_MOCK_BENCH: ~/plesty-tutorial/bench}
    autostart: true
  k10cr1:
    package: plesty-k10cr1
    git: https://gitlab.com/plesty/hub/devices/thorlab/plesty-k10cr1.git
    ref: demo/mock-replay
    args: [--mock]
    env: {PLESTY_MOCK_BENCH: ~/plesty-tutorial/bench}
    autostart: true
  spectrometer:
    package: plesty-lightfield-spectrometer
    git: https://gitlab.com/plesty/hub/devices/princeton_instruments/lightfield_spectrometer.git
    ref: demo/mock-replay
    args: [--mock]
    env: {PLESTY_MOCK_BENCH: ~/plesty-tutorial/bench, DEVICE_DATA_ROOT: ~/plesty-tutorial/data, DEVICE_DATA_PATH: ~/plesty-tutorial/data}
    autostart: true

Then, in that folder, install and start all three:

plesty-server -f fleet.yaml fleet up

NAME          STATE    PID    PORT  STARTED                    DETAIL
pm100d        running  10957  5551  2026-10-26T14:20:42+00:00
k10cr1        running  11011  5552  2026-10-26T14:20:50+00:00
spectrometer  running  11229  5553  2026-10-26T14:20:53+00:00

plesty-server -f fleet.yaml fleet down stops them again. The spectrometer saves each spectrum under ~/plesty-tutorial/data — DEVICE_DATA_ROOT is the one folder it may write in, DEVICE_DATA_PATH where it writes until a run sends it elsewhere. That folder is the shared data disk of this one-PC setup, so the experiment you build points its LOCAL_DATA there too (see The Rig). Every output on these pages is from this setup.

plesty-pow-pl is the production experiment of this measurement.