Sea-Bird Scientific HydroCAT CTD X2 Integration Guide

The Sea-Bird Scientific HydroCAT CTD sensor is compatible with the X2 data logger using the SDI-12 communication protocol and sensor interface. Follow the information below to configure the proper parameters for the sensor and create a generic SDI-12 script using the CONNECT software.

Sea-Bird Scientific HydroCAT CTD product page

Figure 1: Sea-Bird Scientific HydroCAT CTD sensor


Establish Connection

  1. Follow the wiring diagram below to connect your Sea-Bird Scientific HydroCAT CTD sensor to a PC by utilizing the Sea-Bird manufacturer-included MCIL-6-FS to DB9 software cable. An RS232-to-USB converter will be necessary to connect to a PC.
    1. Warning: Ensure the red wire (voltage in) is only wired for the sensor, and has no wiring connection with the RS-232-to-USB converter.
MCIL-6-FS Pin #DB9 Serial Pin #External Wire ColorSignal
15Black + Spare (Both black external wires)GND
23RS232 Rx
32RS232 Tx
6RedVoltage In


  1. Go to the link provided to download the Sea-Bird Scientific UCI software for MAC or Windows.
    1. Open the software once downloaded.
  1. Under the UCI Dashboard tab, click Connect. A separate Connect window will open. Enter the following settings:
    1. Instrument Type: HydroCAT
    2. Baud Rate: 19200
    3. Correct COM port
  1. Click Connect when the settings are input.

Figure 2: Click connect to begin communicating with the sensor.


  1. Once connected, the Connection Mode at the top left will display Setup in green, along with the internal sensor diagnostics.

Figure 3: Successful sensor connection is indicated by the green ‘Setup’ indicator.


Configure SDI-12 Output and Parameters

  1. Open the HydroCAT command terminal by going to Sensor | HydroCAT (no optics) | Command Terminal. 

Figure 4: Access the HydroCAT command terminal.

Figure 5: HydroCAT command terminal with the ‘GetCD’ command input.


  1. Set the output format to SDI-12 Engineering by selecting OutputFormat=[value] from the drop-down menu. Replace [value] with the number 3 and click Submit.
    1. The command terminal should successfully display <Executed/> before and after the command.

Figure 6: Successful SDI-12 Engineering output command.


  1. Go to the HydroCAT Settings by following HydroCAT (no optics) | HydroCAT Settings.

Figure 7: Open the HydroCAT Settings.


  1. Modify the output format to the following parameters and units:
Sound Velocitym/sec
Specific ConductivityS/m


Figure 8: Correct output format.


  1. Return to the Command Terminal and enter ts into the command line and  press Submit.
    1. This command should return the following output in order, separated by either a + or – sign (depending on a positive or negative measurement):
      • SDI-12 Address
      • Temperture
      • Conductivity
      • Pressure
      • Oxygen
      • Salinity
      • Sound Velocity
      • Specific Conductivity
        • e.g. SDI-12 Address + Temperature – Conductivity – Pressure + Oxygen + Salinity + Sound Velocity – Specific Conductivity

Figure 9: ts output command.


Create a Generic SDI-12 Script

  • After the sensor output has been changed, a Generic SDI-12 script will need to be generated in the CONNECT software following the outline below:
    1. Manufacturer: Sea-Bird
    2. Model: HydroCAT SDI12
    3. SDI-12 Address: Must match the address input in the UCI software.
    4. Port: Must match the port in which the HydroCAT will be detected.
    5. Warmup: Recommended 30 seconds.
    6. Meas Cmd: Set as the ‘C’ command to avoid any interference with other SDI-12 sensors.
    7. Power: Recommended switch power
    8. Selected Parameters: Must match the parameter configuration set in the UCI software.

Figure 10: Sea-Bird HydroCAT generic SDI-12 CONNECT script.


  • Once completed, transfer the script file onto the X2 and follow the detection process outlined in your included X2 Quick Start Guide, unless the X2 detection has been completed by NexSens prior to shipment.


Conductivity, Temperature, and Depth Measurements

Learn more about CTD measurements in the Fondriest Environmental Learning Center.