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LABMETRIC · RESOURCES

Downloads, manuals and lessons.

Everything for ohmSTAR and ohmSTAR+, one click away.

The box's screen showing a large USB mark, because a computer is connected.

MANUALS

Read every manual right here.

Turn the pages like a book, one or two at a time.

CODE AND AI CONTROL

Pick a route. One line gets you started.

You wantUse
At the screenThe app, or its AI assistant
Scripts, app openHTTP API or MCP
Scripts, app closedCommand line or Python
LabVIEW, MATLAB, TestStandRaw serial

AI control

Plain words, from the built-in assistant or your own agent.

Claude Code
claude mcp add --transport http --scope user ohmstar http://127.0.0.1:8765/mcp --header 'Authorization: Bearer ${OHMSTAR_TOKEN}'
  • Turn on Allow AI control; token in OHMSTAR_TOKEN.
  • Asks before every change. Never touches calibration or firmware.
Claude Desktop extension (31 KB)Short guide 05

Command line

Terminals and scripts. Node.js 20+.

Terminal
ohmstar temp pt100 77 --unit F
Set 109.74 Ω (Pt100 at 25 °C) on the ohmSTAR+
  • Disconnect the app first: one program per box.
  • Exit 0 worked, 1 refused, 2 typo. --json for scripts.
Download the tool (ZIP, 1.3 MB)Short guide 02

HTTP API

Any language, while the app keeps logging.

curl
curl -X POST http://127.0.0.1:8765/v1/resistance -H "Authorization: Bearer $OHMSTAR_TOKEN" -H "Content-Type: application/json" -d '{"value":"10k"}'
  • Start it under Local network API; port 8765, token on every request.
  • This computer only, unless you allow the network.
Short guide 03

Python

Test scripts over USB. Python 3.9+.

Python
from ohmstar import Box, MockBox
with Box(MockBox("ohmSTAR+")) as box:
    box.set_sensor("pt100", 25)   # 109.74 Ω
  • Not on PyPI yet: ask us for the package.
  • MockBox behaves like a real box, so tests need no hardware.
Python package (.whl, 272 KB)Short guide 04

Raw serial

9600 baud, 8N1, for serial-only programs.

Serial
r4700
Sets 4,700 Ω
Short guide 01
Missing something? Suggest a feature

CLASSROOM LAB

Three lessons. Real boxes, or none.

Each one fits on a one-page handout: open it in the viewer above, or print the PDF.

Lesson 1 · Ohm's law

Choose the resistor for an LED

Use the box as the series resistor, watch the LED change, and work out the right value.

You need A 5 V supply, an LED, a meter for the current, and a box.

  1. Set upSet I set to 5 V, at the box or on the Device page keypad. Wire the supply, the box, the LED and the meter in series.
  2. In classStart at 1000 Ω and step down. Record the current and how bright the LED looks.
  3. Hand inWork out the resistor for 20 mA, then set it on the box to check.
+5 V ohmSTAR mA R LED
Worked example: 5 V supply, 2.0 V LED
ΩmA
10003.0
4706.4
3309.1
22013.6
15020.0

R = (supply − LED voltage) ÷ current. Set I set first: it protects the box's 1 W rating.

Open the handout PDF, 1 page

Lesson 2 · Data collection

Build a test station with Sequences

Turn the box into a repeatable test: set points in a sequence, every reading collected into a report.

You need A device with a sensor input (here a Pt100 controller), a box and the Companion.

  1. PlanIn Sequences and reports, make a sequence: one step per check, each with a value, a label and what to check.
  2. RunConnect the box to the sensor input. Run the sequence with Unit under test and Operator filled in. Type each reading; mark Pass, Fail or Skip.
  3. CollectSave PDF or Save CSV. Every run is kept in Reports, and every value sent is in the day’s CSV log.
Example sequence: Pt100, IEC 60751
°CΩ
0100.00
50119.40
100138.51
150157.33
200175.86

The same steps fit a thermostat, a PLC input or a data logger: change the test points.

Open the handout PDF, 1 page

Lesson 3 · Strain gauge

A quarter bridge you build

Build a strain gauge bridge and find the gauge factor from your own plot.

You need Three 350 Ω resistors, 5 V excitation, a meter for the output, and a box.

  1. BuildWire three 350 Ω resistors with the box as the fourth arm. Set 350.00 Ω and null the bridge.
  2. MeasureStep through the test points. Record the output at 5 V excitation.
  3. Hand inPlot output against strain. The slope gives the gauge factor.
V +5 V 350 Ω350 Ω 350 ΩohmSTAR
350 Ω gauge, GF 2.0: R = R0 × (1 + GF × ε)
µεΩ
0350.00
500350.35
1000350.70
2000351.40

An ohmSTAR+ sets these exactly; an ohmSTAR rounds them to 0.1 Ω.

Open the handout PDF, 1 page

Every lesson runs on any of these

  • A box per benchCompanion preset: Just the box, or Standard
  • Many boxes, one computerMultiple boxes page: Set each, or Set all
  • No boxes yetMock ohmSTAR or ohmSTAR+ in the app; MockBox in Python
  • One instructor computerHTTP API on each bench, one token per bench
Classroom lab guide More lab ideas Education pricing for schools

TROUBLESHOOTING

Stuck? Start with ohmstar info.

The box isn't found

Check power and cable, then press Detect. On battery it sleeps after about 5 minutes.

Another program has it

One program per box: disconnect the app, close terminals.

"Nothing was sent"

Out of range, or 1.5m: use a capital M.

401 or 403 from the API

Wrong token, or AI control is off. Dock apps don't read ~/.zshrc.

The screen shows °C, not ohms

A table is active: choose table 0 at the keypad.

Still stuck

Contact us with the message, model and firmware, or read the guide.

COMPATIBILITY

Will it work with my setup?

Windows

10 or 11, x64. Not signed yet: More info, Run anyway.

macOS

13+, Apple chip or Intel. First launch: right-click, Open.

Linux

64-bit (x86_64), as an AppImage.

USB

Mini-USB, the older D-shaped plug. FTDI serial chip; drivers install themselves.

Boxes

ohmSTAR 1 Ω–25 MΩ, 0.1 Ω steps. ohmSTAR+ 1 Ω–5 MΩ, 0.01 Ω.

AI assistant

Claude, OpenAI, Gemini and more with your key, or local models (Ollama, LM Studio).

Calibration bench

Tried and true. Needs an HP/Agilent 34401A.

Scripting

Python 3.8+ with pyserial, or Node.js 20+ for the command-line tool.

Firmware upgrade · $54.95

Older box? Send it in once and unlock the Companion.

Boxes on firmware before 7.x can't use the Companion app. We bring yours up to the newest firmware and send it back. A calibration includes the upgrade free.

Request the upgradePrice and turnaround
  • The Companion appValues, sweeps, sequences, logging, tables, the API and AI control.
  • Live read-backThe box reports its real output, and whether a table is active.
  • The box's own recordSerial number, calibration dates and sheet, stored on the box.
  • All 14 memories and quick keysRead and stored from the app.
  • Standby and display settingsSet from the app.
  • Every update after that is freeOver USB from the Companion. No programmer, no shipping.

FIRMWARE BEFORE 6.1

Legacy tools: still supported.

Older boxes keep working. We can update yours by mail.

ohmSTAR ConsoleWindows 7 and up · Mac · Linux. Loads, makes and checks sensor tables, and sets values, from any lab PC. Nothing to install.

Download (ZIP, 7.7 MB)

Original user manualRev C (OS22), 12 pages.

Read it

USB driverIf Windows doesn't install it.

FTDI VCP drivers

Any serial terminal9600 8N1; end commands with CR or LF.

  1. Save a two-column table (unit, ohms) as .txt.
  2. Load it with the ohmSTAR Console.
  3. Press TABLE.
Serial commands from the original manual (Rev C)
CommandDoesReply
r<value>Set a resistance, e.g. r5.123ACK
t,0,xRead calibration point x (0–31)t,0,x,value
T,0,x,value,DOWrite calibration point xACK
T,n,0,name / T,n,1,unitName or unit of table n (1–9)ACK
T,n,2,-1Erase table nACK
T,n,3,user,ohmsAdd a point to table nACK
t,n,pRead one entry (t,n,2 = points)t,n,p,value
t,nDump table n (0 = calibration)Every entry

Email us about an old box.

App notes Simulate any resistive sensor Calibrate a PID controller with a Pt100 Video: Pt RTD, PID controller calibration All app notes