Atlas Scientific EZO Sensors — MCP Server

Let an AI agent read, calibrate and log Atlas Scientific EZO™ sensor circuits (pH, ORP, dissolved oxygen, conductivity, RTD temperature, humidity, CO2 and pressure) over their documented UART command set. Useful for bioreactors, cell-culture media, fermentation, hydroponics, aquaculture and environmental monitoring.

Try it without hardware

uvx labmcp-atlas-ezo --simulate --check
uvx labmcp-atlas-ezo --simulate --option sim_sensor=DO --check     # also ORP, EC, RTD, HUM, CO2, PRS

Connect your instrument

1. Circuit setup: the circuit must be in UART mode (LED green/cyan; blue means I2C mode, see "Change to UART mode" in the datasheet). Factory settings are 9600 baud, 8 data bits, no parity, 1 stop bit, no flow control, CR line endings. Cross TX/RX between the circuit and the adapter, and use an electrically isolated carrier board when the probe sits in the same liquid as other probes or pumps.
2. Find the port: uvx labmcp ports
3. Test the connection:

   uvx labmcp-atlas-ezo --address /dev/ttyUSB0 --check                # Linux
   uvx labmcp-atlas-ezo --address /dev/tty.usbserial-XXXX --check     # macOS
   uvx labmcp-atlas-ezo --address COM5 --check                        # Windows
   uvx labmcp-atlas-ezo --address "serial://COM5?baudrate=38400" --check   # non-default baud rate

   On connect the server sends C,0 (continuous readings off, so replies are not interleaved with readings) and *OK,1 (response codes on, the factory default). The circuit keeps both settings across power cycles.

Add to your MCP client

Claude Code

claude mcp add ph-probe -- uvx labmcp-atlas-ezo --address /dev/ttyUSB0

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

{
  "mcpServers": {
    "ph-probe": {
      "command": "uvx",
      "args": ["labmcp-atlas-ezo", "--address", "/dev/ttyUSB0"]
    },
    "do-probe": {
      "command": "uvx",
      "args": ["labmcp-atlas-ezo", "--address", "/dev/ttyUSB1"]
    }
  }
}

Run one server per circuit. Add --read-only to allow readings but block calibration and settings changes. For other clients, generate the snippet with uvx labmcp config atlas-ezo --address /dev/ttyUSB0 --client vscode.

Tools

get_connection_info, get_command_log and reconnect are built into every LabMCP server.

Safety limits

Override at launch: --limit max_series_duration_s=3600 (3600 s is the most one log_series call can run; split longer logs into several calls). log_series writes its optional save_path only to a new .csv file (existing files are never overwritten). These circuits only measure, so there are no hazardous tools; the risk is a bad calibration, which is why calibrate validates point names and standard values per circuit type and clear_calibration is hidden in --read-only mode.

Example prompts

• "What sensor is connected, is it calibrated, and what's the pH slope?"
• "The pH probe is in pH 7.00 buffer. Log it every 2 s until it's stable to ±0.01, then calibrate the midpoint. Then walk me through pH 4 and pH 10."
• "The bioreactor is at 37 °C: set the temperature compensation and read the dissolved oxygen in mg/L and % saturation."
• "Log conductivity, TDS and salinity every 30 s for 10 minutes and tell me whether the nutrient solution is drifting."
• "Turn off the LED on the DO circuit, we're running a light-sensitive culture."

Notes

• Units per circuit: pH; ORP in mV; DO in mg/L and (if enabled with O,%,1) % saturation; EC in µS/cm plus TDS (ppm), salinity (PSU) and specific gravity when enabled; RTD in its configured scale (°C/K/°F); HUM in %RH plus air temperature and dew point (°C) when enabled; CO2 in ppm (+ internal temperature); PRS in its configured unit (psi, atm, bar, kPa, inH2O, cmH2O). Which outputs are enabled is read from the circuit (O,?, S,?, U,?) rather than assumed.
• Output order of multi-value readings follows the datasheets (EC: EC,TDS,S,SG). The DO order (mg/L then % saturation) is not spelled out in the DO datasheet; it was cross-checked against the open-source EnviroDIY ModularSensors and feastorg ezo-driver libraries. Please report if your circuit differs.
• Temperature compensation (T,n, pH/EC/DO only) and DO salinity/pressure compensation are not retained when the circuit loses power; set them again after a power cycle. Readings report the compensation temperature in use.
• Calibration rules enforced: pH midpoint must be calibrated before low/high (a new mid erases low/high, as the datasheet warns), with mid 6-8, low 0-6.5 and high 7.5-14; ORP ±1020 mV; EC 0.07-500,000 µS/cm (do dry first); CO2 high point 3000-5000 ppm; RTD -126 to 1254 °C. The server cannot see which standard the probe is actually in: the agent must confirm that with you.
• An RTD reading of -1023 means no probe is connected; the reading includes a warning.
• DO queries such as P,? answer ?,P,90.25 (note the extra comma) per the datasheet; the driver accepts both forms. The DO salinity reply contains a micro sign, so the port is read as Latin-1.
• Not exposed as tools (verified but not useful or too risky for an agent): Factory (erases calibration), Sleep, Find, Baud, I2C, Plock, calibration Export/Import, the RTD data logger, and the HUM/CO2/PRS alarm pins. EZO pumps (EZO-PMP) and other actuator circuits are refused on connect.

Hardware verification