Performing calibration adjustment - FD70

FD70 Configuration and Maintenance Guide
Document code
M212222EN
Revision
J
Language
English
Product
FD70
Document type
User guide
Do not perform calibration adjustment indoors.
  • Field calibrator kit for FD70 (FDA701)
  • Maintenance laptop with terminal software
  • Soft, lint-free cloths (2 pcs)
  • 50 % isopropyl alcohol

FD70 has a transmitter, a main receiver and a side receiver, depending on the configuration you have chosen. The following procedure describes the general calibration adjustment steps. Perform calibration for the main receiver and transmitter, and then perform the same calibration steps for side receiver and transmitter.

During the calibration adjustment, measurement data is invalid.
Calibration adjustment (mode adjust) sets new values related to the scatter measurement and window contamination measurement.
Requirements for calibration adjustment
Property Requirement
Visibility > 2000 m (6560 ft)
Present weather Calibration is not recommended in heavy rain or in bright sunshine.

Calibration adjustment is needed:

  • If the window contamination status is not OK after window cleaning.
  • If the calibration check is not OK after running mode calcheck command.
  • When the transmitter or receiver module is replaced.
  • When the transmitter or receiver hood is replaced.

Calibration adjustment has the following phases:

  • Preparation
  • Zero signal measurement
  • Scatter signal measurement
  • Scatter measurement adjustment

The result is:

  • Pass: the calibration adjustment is valid
  • Fail: the calibration adjustment is not valid. If it fails several times, contact Vaisala.

If you cancel the process at any point, the previous values are restored.

  1. Before you start, check the opaque glass of the calibrators and clean them if necessary.
    1
    Calibrator
    2
    Opaque glass
    Be careful not to scratch the calibrators, especially the opaque glass. Damaged calibrators have a negative effect on the calibration.
  2. Establish a maintenance connection to FD70.
  3. Type the following commands: 
    level 2
    mode adjust

    For the side receiver, type the following command:

    mode adjust 2

    Follow the onscreen instructions.

  4. When prompted, do the following.
    1. Using low pressure, spray 50 % isopropyl alcohol on the glass windows. Spray enough solution to dissolve and loosen any dirt.
    2. Wipe the window with a soft, lint-free cloth until the window is clean.
    3. Take a new cloth and wipe the window until it is clean.
    4. Wait until the windows are dry.
    During window cleaning, keep the interface unit door closed.
    CAUTION Do not use pressure washers.
    CAUTION Be careful not to scratch the window surfaces or touch the measurement unit windows with bare hands.
    • If the clean window check passes after window cleaning, the current clean window reference is not changed and adjustment can continue to calibration check.
    • If the clean window check fails after 2 successive cleaning attempts, follow the onscreen prompts and either choose to set a new clean window reference and continue (type Y), or cancel the adjustment (type N).
  5. When prompted for Calibrator Signal Value, type the 4‑digit value.

    The same value is printed on the calibrator certificate, on the calibrator labels, and the calibrator case.

  6. When prompted to install the calibrators with zero signal plates, remove the protection caps from the transmitter and receivers.
  7. Attach the calibrators with zero signal plates on the transmitter and receiver.

    There is a dedicated calibrator for the transmitter and one for the receivers. Check the labels on the calibrators to make sure that you attach them correctly. The following figures show the calibrator attachment process for the main receiver and the side receiver.

    1
    Transmitter
    2
    Side receiver
    3
    Main receiver
    4
    Calibrator for transmitter (labeled)
    5
    Calibrator for receivers (labeled)
    6
    Zero signal plate (2 pcs)
    7
    Thumb screw (2 pcs / calibrator)
    1
    Transmitter
    2
    Side receiver
    3
    Main receiver
    4
    Calibrator for transmitter (labeled)
    5
    Calibrator for receivers (labeled)
    6
    Zero signal plate (2 pcs)
    7
    Thumb screw (2 pcs / calibrator)

    The system performs zero signal measurement.

    • The limit is ±0.012 for the main receiver and ±0.04 for the side receiver.

    • If the zero signal measurement fails, eliminate all possible reflections and external light sources.

  8. When prompted, remove the zero signal plates.

    The system performs scatter signal measurement.

  9. Adjust the scatter measurement.
  10. Verify the scatter measurement.

    • The scatter measurement passes if the scatter signal value is within 3 % of the calibrator signal value.

    • If the signal measurement fails, try calibration adjustment again (mode adjust, mode adjust 2). If measurement fails several times, contact Vaisala.

  11. After completing the calibration adjustment for the main receiver, repeat the process for the side receiver.
  12. When done, remove the calibrators, reattach the protection caps on the transmitter and receivers, and close the maintenance connection. 
    close

The calibration adjustment date is stored in the system as metadata.