Troubleshooting power and communications

Troubleshooting power and communications

If none of the troubleshooting questions or resolutions below address your issue, please contact us through the live chat, email (, or phone (+1.888.290.6060). We’ll do all we can to help you resolve your issue.

The display does not turn on.

  • Check the power and ground connections to your instrument.

The display is dim or weak.

  • Check the power and ground connections to your instrument.
  • Check the display contrast settings by selecting MENU > ADV SETUP > DISP SETUP > LCD CONTRAST. The default contrast level set at the factory is 10.

The buttons on the display do not respond, and ‘LCK’ appears on the screen.

Alicat devices come with a display locking option to prevent inadvertent changes to setpoints or settings. If the error code ‘LCK’ appears on the screen, your device display has been locked.

  • If your device was manufactured with firmware version 6v or later, you can unlock the display by pressing and holding the buttons located at the four corners of the display until ‘LCK’ disappears.
  • All devices equipped with our standard serial communications can be unlocked by issuing the following serial command: [Unit ID]$$U<CR>. (Replace [Unit ID] with your device’s single letter Unit ID.)

The analog output signal indicates values lower than what appears on my instrument’s display.

Analog signal voltage degrades over long distances. You can minimize this effect by using wires with a heavier gauge, especially in the ground wire.

How can I connect my Alicat to my computer serially?

Nearly all Alicat instruments are manufactured with digital serial communications. Follow the steps below to establish a connection to your Alicat from your Windows computer:

    1. Download our Serial Terminal program.
    2. If you are connecting with a USB cable, install the USB driver. This creates a virtual COM port on your computer.
    3. Open your computer’s Control Panel, and then open Device Manager.
    4. Under “Ports (COM & LPT)”, find the COM port number that is connected to your Alicat. If you are using a USB cable, the virtual COM port will be called “USB Serial Port (COM#)”. Take note of the COM port number.
    5. Open the Serial Terminal program.
    6. Serial Terminal will ask for the COM port and baud rate. Enter the COM port you found above and the default baud rate of 19200.
    7. Type the single-letter Unit ID for your Alicat instrument, and press enter <CR>. If you do not know your device’s Unit ID, you can find it by selecting MENU > ADV SETUP > COMM SETUP on the display.
    8. If your computer returns a line of data after Step 7 above, you have successfully established serial communications.

My computer cannot communicate with the Alicat over my serial connection.

  • Check that your unit is powered on and connected to your computer properly. See above instructions to connect your instrument.
  • Be sure that the COM port on the computer to which the Alicat is connected is active. Open Device Manager to confirm that the COM port is visible.
  • When connecting multiple devices to a single COM port (or virtual COM port if using USB), be sure to give each Alicat device a unique Unit ID. You can change the Unit ID by selecting MENU > ADV SETUP > COMM SETUP > UNIT ID.
  • Alicat’s RS-232 output uses a 0-5 Vdc signal. See this document for details: RS-232 Output Specifications.

My computer cannot find my BB3 or BB9 multi-drop breakout box.

  • If your BB3 or BB9 multi-drop box is showing up under “other” in your device manager instead of “Ports (COM & LPT)”, the most likely cause is a missing driver. While this should install automatically when plugging into your computer, occasionally security settings can prohibit it from installing. You can download and install the driver manually from our Software & Drivers page.
  • If you are using a USB port with Windows 7 and receive the error, “One of the USB devices attached to this computer has malfunctioned and Windows does not recognize it”, the USB port itself is not responding properly. Microsoft has released a solution on its forum.
  • If you are using the 9-pin serial connection on your computer and your COM port does not appear in Device Manager, the COM port on the computer or the cable may have stopped functioning. Please try connecting to the computer using a different cable or different port (USB), and check Device Manager again.

The FlowVision SC or MX sofware displays an error that begins with “Method not found: ‘System.String…'”

FlowVision SC and MX require that your computer is running the most recent Microsoft .NET framework. You can download this at

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