JULABO Circulator — MCP Server

Let an AI agent run JULABO heating and refrigerated circulators through JULABO's documented interface commands: read the bath and external temperatures and the heating/cooling power, set the setpoint, start and stop temperature control, decode status and alarm messages, and wait until the bath is stable at temperature.

Try it without hardware

uvx labmcp-julabo --simulate --check

Connect your circulator

1. Enable remote control on the circulator. Without it the circulator answers queries but ignores every setting command.
   • CORIO CD/CP: MENU → IntE → rEM → USb (or 232 for RS-232). rOFF appears in standby.
   • MAGIO / DYNEO: Main menu → Connect unit → Remote control → USB or RS232. An "R" appears in the status bar.
2. Cable: USB-B (the circulator appears as a virtual COM port; on Windows install JULABO's USB driver) or a null-modem RS-232 cable. RS-232 factory settings: 4800 baud, 7 data bits, even parity, 1 stop bit, hardware handshake (RTS/CTS). Interface parameters can only be changed while remote control is off. The server uses these settings but does not enforce the handshake by default (it keeps RTS asserted, which lets the circulator transmit, and USB virtual COM ports often never assert CTS); add ?rtscts=true to the address to enforce it.
3. Find the port: uvx labmcp ports
4. Test the connection:

   uvx labmcp-julabo --address /dev/ttyACM0 --check                  # Linux (USB)
   uvx labmcp-julabo --address /dev/tty.usbmodem1101 --check         # macOS
   uvx labmcp-julabo --address COM3 --check                          # Windows
   uvx labmcp-julabo --address "serial://COM3?baudrate=9600" --check # RS-232, non-default baud rate
   

   --check prints the firmware string (version) and the current status, e.g. 02 REMOTE STOP.

Add to your MCP client

Claude Code

claude mcp add julabo -- uvx labmcp-julabo --address /dev/ttyACM0

Claude Desktop / Cursor / Windsurf (claude_desktop_config.json, .cursor/mcp.json, …)

{
  "mcpServers": {
    "julabo": {
      "command": "uvx",
      "args": ["labmcp-julabo", "--address", "/dev/ttyACM0", "--limit", "max_temperature_c=120"]
    }
  }
}

Add --read-only to allow monitoring only (stop_circulation stays available). For other clients: uvx labmcp config julabo-circulator --address /dev/ttyACM0 --client vscode.

Tools

Safety limits

The defaults suit a water bath. Set them to your bath fluid's working range, e.g. --limit min_temperature_c=-30 --limit max_temperature_c=150 for a silicone oil / glycol-rated setup. The circulator additionally enforces its own working range, warning limits and excess-temperature protection; rejections come back as errors such as -11 VALUE TOO LARGE.

Example prompts

• "Set the circulator to 37 °C, start it and tell me when the bath has been stable within ±0.1 °C for five minutes."
• "What's the bath temperature and how hard is the circulator working right now?"
• "Cool the jacketed reactor to 10 °C using the external Pt100 as the reference and let me know when it gets there."
• "Is there any alarm on the circulator? Explain what it means."
• "Stop the circulator."

Notes

• Remote control is a front-panel setting. In manual mode (00 MANUAL STOP / 01 MANUAL START) the server refuses to send settings and tells you how to enable remote control.
• Every setting is verified. OUT commands have no reply, so after each one the server queries status (to catch -08 INVALID COMMAND, -09 COMMAND NOT ALLOWED IN CURRENT OPERATING MODE, -10 VALUE TOO SMALL, -11 VALUE TOO LARGE, -13 VALUE EXCEEDS TEMPERATURE LIMITS) and reads the setpoint or in_mode_05 back. stop_circulation retries once and reports an error if the circulator still says it is running.
• Model differences. CORIO CD has only the basic set (actual value, power, safety sensor, setpoint, start/stop). Warning limits (in_sp_03/04) need CORIO CP, MAGIO or DYNEO; the external Pt100 (in_pv_02) needs MAGIO or DYNEO. The server detects missing commands (no reply) and reports those values as null.
• Command pacing (unverified). The manuals give no minimum time between commands. The server waits command_delay_s (default 0.25 s) after each setting command before checking status; change it with --option command_delay_s=0.5 if your circulator misses commands.
• Watchdog. MAGIO/DYNEO circulators have a watchdog configured in their own menu (mode, timeout, fallback setpoint, reset on "setpoint only" or "all valid commands"). The server does not configure it. With restart mode "all valid commands" you can keep it fed while the server runs with --option keepalive_s=10 (queries status every 10 s). JULABO's alarm list notes that it expects the setpoint at least every 30 s in "setpoint" restart mode, which this keep-alive does not do.
• Status and alarm texts are decoded from the code (-01, -14, -63, ...) using the alarm tables in the manuals; the exact wording the circulator sends is passed through unchanged.
• Not implemented: pump stage/capacity (out_sp_07/27), warning-limit writes (out_sp_03/04), controller parameters (out_par_*), external/internal control switch (out_mode_04), EPROG and ATC calibration commands.

Hardware verification