Python package

Install

pip install benchmesh              # the client, no dependencies
pip install "benchmesh[pandas]"    # plus pandas for DataFrames

The BenchMesh app (or benchmesh-server) must be running: the package talks to its API at http://127.0.0.1:57666 on the same computer. Nothing needs to be switched on for that.

Quick start

import benchmesh

bench = benchmesh.connect()            # $BENCHMESH_URL or http://127.0.0.1:57666

for inst in bench.instruments():
    print(inst.id, inst.classes, inst.model, "online" if inst.online else "offline")

psu = bench["tenma-72-2540"]           # the id from the Instruments drawer
psu.set("voltage", 5.0)                # checked by the server against 0-60 V
psu.set("output", "ON")                # switches the output on at once
print(psu.read("VOUT"))                # latest reading: 4.94 (float, volts)
print(psu.status())                    # {"VOUT": 4.94, "IOUT": 0.012, "OUTPUT": "ON", ...}
print(psu.query("voltage"))            # asks the instrument now
psu.set("output", "OFF")

Every instrument of a class works the same way; names, limits, ranges and modes come from the instrument’s definition, exactly as in the app. An instrument with several classes takes cls=, a multi-channel one ch=:

spm = bench["owon-spm3103"]             # a supply with a built-in meter
spm.set("voltage", 3.3, cls="PSU")
spm.read("MEAS", cls="DMM")
scope.set("scale", 0.5, ch=2)          # channels 1-9, default 1

Values

• Measured values become float in base units (V, A, W, Ω). A meter that reports something that is not a number (such as OL) gives that text back.
• Modes and switches are strings ("ON", "VOLT"), flags bool, missing values None, binary results bytes.
• raw=True on query, read and status returns the server’s JSON unchanged.
• Setter values are sent as given and checked by the server against the definition; an invalid one raises BadRequest before anything reaches the instrument.

Read a meter, adjust a load

The classic bench loop: hold 5 V on a source by raising or lowering an electronic load’s current while a separate meter watches the voltage. bench.watch() reads the latest values BenchMesh already polls, so the loop adds no traffic to the instruments.

import benchmesh

bench = benchmesh.connect()
load = bench["owon-oel1515"]
current = 0.0
load.set("mode", "CURR")
load.set("curr", current)
load.set("input", "ON")                # the load starts drawing current
try:
    for t, values in bench.watch({"v": ("owon-xdm1241", "DMM", "MEAS")}, interval=0.5, duration=60):
        v = values["v"]
        if v is None:
            continue                   # meter offline
        current = min(current + 0.01, 1.0) if v > 5.0 else max(current - 0.01, 0.0)
        load.set("curr", round(current, 3))
finally:
    load.set("input", "OFF")

For loops that must keep running when your script does not - unattended, with a guaranteed cleanup - write a flow instead; the app runs it with the same safety rules as everything else.

Recordings in pandas

The app records on whole seconds on one shared timeline; your script only steps the voltage. The recording appears in the app’s Recording drawer as well:

import time
import benchmesh

bench = benchmesh.connect()
psu = bench["tenma-72-2540"]
psu.set("voltage", 1.0)
psu.set("output", "ON")
try:
    with bench.record("sweep", {"vout": (psu.id, "PSU", "VOUT"),
                                "meter": ("owon-xdm1241", "DMM", "MEAS")}) as rec:
        for v in (1.0, 2.0, 3.0, 4.0, 5.0):
            psu.set("voltage", v)
            time.sleep(2)
finally:
    psu.set("output", "OFF")

df = rec.to_pandas()                   # index: time (UTC), one column per label
df.plot()

Older recordings, for example in a Jupyter notebook (pip install "benchmesh[pandas]"):

rec = bench.recordings()[0]             # newest first
df = rec.to_pandas()
df.resample("10s").mean().plot(subplots=True)

rec.data() returns plain lists {label: (times_s, values)} without pandas, and rec.export_csv() the CSV the app exports.

Automation flows

for f in bench.flows():
    print(f.id, f.name)

status = bench.run_flow("hold-5v", params={"target": 4.8}, arm=True,
                        on_event=lambda e: print(e["msg"]))
print(status.state, status.vars)       # "finished" / "failed" / "aborted"

A flow that can switch outputs on needs arm=True, otherwise the server refuses it with Refused. run_flow waits until the run ends; a timeout or Ctrl-C aborts it, and its cleanup still runs.

From another computer

On the bench computer switch on remote access (Instruments → Remote access: a password, then the switch) and note the address and the certificate fingerprint. Then, on any computer of your local network:

bench = benchmesh.connect(
    "https://192.168.1.20:57667",
    password="the password",
    fingerprint="AB:CD:...:EF",        # as shown in the app; case and colons do not matter
)

The certificate is the app’s own, so the package pins it: right after the TLS handshake it compares the certificate’s SHA-256 fingerprint with the one you give, and only then sends the password. BENCHMESH_URL, BENCHMESH_PASSWORD and BENCHMESH_FINGERPRINT can replace the arguments. Signed in with the view-only password, reads, watch and recordings work and every change raises AuthenticationError (403).

Reference

A signal is (device_id, class, field) or (device_id, class, field, channel). Prefer existing VISA code? Every instrument also answers SCPI on a virtual SCPI port.

Errors

All are BenchMeshError with .status and .detail, the server’s message.