Visibility calibration

The sensor can be checked and adjusted using the optional calibration kit. The calibration must be run using the menu system. Campbell Scientific Device Configuration Utility program includes a terminal emulation screen that allows access to the onboard menu. The calibration procedure requires a sensor calibrator disk and a computer with a standard serial port compatible with the sensor. If your sensor is not configured for RS-232 communications, switch internal switch 3 to ON, which sets the sensor communications port to RS-232 with a 38400 bps baud rate (see Internal switches). If the sensor is already set to the RS-232 mode, the internal switch does not need to be changed.

NOTE:

Ideally perform the test in the following conditions:

  • Ambient temperature: 0 to 50 °C

  • Local visibility: approximately 10,000 m or higher.

  • The system is self-regulating. However, it is recommended the sensor is calibrated at least every two years.

  1. Clean lenses using pure alcohol or diluted detergent and a lint free cotton cloth. Refer to the Cleaning for more information. A simple visual check may be enough to confirm the lenses are clean.

  2. Connect computer with Device Configuration Utility software to the RS-232 or Micro USB port on the data logger. Select the Terminal tab. Press Enter twice for the prompt (for example, CR1000x>). Type P and press Enter. Type the CS120A/CS125 serial port and press Enter.

  3. Type open 0 and press Enter to access the CS120A/CS125 Setup Menu.

  4. Type 3 and press enter for the Calibration Menu.

    CS125 CALIBRATION MENU 3

    ID 0

    S/N 1003

    (1) Perform calibration

    (2) Restore the factory calibration

    (3) Perform dirty windows zero offset calibration

    (4) Restore dirty windows factory calibration

     

    (9) Refresh

    (0) Return to main menu

     

    ->

  5. Select option 1 to start the calibration process. When prompted, type Y to perform a calibration. Please note, after typing Y, the calibration process can not be exited until the test is complete. However, power cycling the unit at this point will have no adverse effect on the sensor.

    Do you want to perform a calibration Y/N?

    NOTE:

    A confirmation is included at each calibration step to correct typing mistakes. Pressing Enter is not required after typing y.

  6. When prompted, type the sensor calibrator serial number and extinction coefficient (EXCO) with a confirmation at each step.

    NOTE:

    Do not type the E at the beginning of the calibration disk serial number.

    Do you want to perform a calibration (Y/N)? Y

    Starting calibration.

    Input the calibration disk serial number ->2000

    Is 2000 correct? (Y/N)? Y

    Input the calibration disk EXCO ->23.7

    Is 23.7 correct? (Y/N)? Y

     

    Place one calibration bung into each hood, then

    press any key.

  7. Place the foam bungs into the sensor hoods (see Calibration disk). The bungs are designed to block all light from the outside reaching inside the head. Place one bung into each hood. If either of the bungs are damaged or appear to have any gaps around the edge, contact Campbell Scientific (see Assistance for more information).

    Calibration disk

    Starting dark level calibration.

    This test will take approximately two minutes.

    This part of the test will take approximately two minutes. Every ten seconds a dot should appear indicating that the test is progressing as normal.

    Dark level test complete. Please remove the bungs.

    Now place the sensor calibrator into the sampling volume.

    Press any key once this is done.

  8. When instructed, remove the bungs.

  9. Place the sensor calibrator into the volume by fastening it to the central mounting point (see Mounting calibration disk).

    NOTE:

    At this stage, it is advisable to perform a simple visual check of the cleanliness of the calibration plate. If contaminated, clean it on both sides. Refer to Cleaning for more information.

    Mounting calibration disk

    Starting light level calibration.

    This test will take approximately two minutes.

    This part of the test will take approximately two minutes. Every ten seconds, a dot should appear indicating the test is progressing as normal.

    Calibration is now complete.

    Saving user settings.

    Press any key to exit.

    Once the second stage of the test has been completed, the new calibration constants will be saved automatically. All calibration constants, including both the user and the factory setting, can be viewed from menu item 4 from the main menu once the test is completed.

  10. Type 0 and press Enter to return to the Main Menu.

  11. Type 90 and press Enter to save settings and exit the Main Menu.

  12. Press Esc four times to exit the Terminal mode.

  13. Disconnect Device Configuration Utility from the data logger.