:CALibrate:DARK:CHANnel:STARt

Flex Apps:
FlexDCA
FlexRT
Dark Cal Commands

Command Syntax

:CALibrate:DARK:CHANnel{1:8}{A|B|C|D}:STARt

Where the required specifier {1:8}{A|B|C|D} identifies a channel by its module slot number and channel letter. For example, channel 3C (CHANnel3C).

The channel specifier will fail if it does not include a slot number. If instead the suffix's channel letter is missing, the command defaults to letter A. As a result, the best practice is to always explicitly specify the channel by including both the module slot number and channel letter.

Description

Starts a dark calibration on the indicated optical channel. A dark calibration is used to calibrate extinction-ratio measurements. Be sure to indicate the desired channel, for example CHAN1B. The *OPC? query should be used to detect when a portion of the calibration has completed. Use the :CALibrate:CONTinue command to dismiss dialogs that are displayed during a calibration. Use the :CALibrate:DARK:CHANnel:DISCard command to erase an existing dark calibration for the selected channel.

Dark Calibration Applies to Channel/Reference Filter Combination

The dark calibration is performed for the current Channel/Reference Filter combination. If the filter is changed, the channel's dark calibration will no longer be marked as valid. For the most accurate measurements, perform the calibration with the reference filter that you intend to use for your measurements.

For example, consider the situation where no dark calibrations have been performed for Channel 2A and you perform these steps:

  1. Select a 27.7393 GBd reference filter for Channel 2A and perform a dark calibration. The dark calibration is marked as valid.
  2. Select a 28.0500 GBd reference filter for Channel 2A. The dark calibration is now marked as uncalibrated.
  3. Select the original 27.7393 GBd reference filter for Channel 2A. The dark calibration is again marked as valid.

When to Perform a Dark Cal

A Dark Level calibration is very sensitive to environmental changes and as a result should be frequently performed. A Dark Level calibration is recommended when one of the following changes occurs:

  • Channel filter rate has changed.
    • Details message: This optional calibration has not been performed.
  • Module is moved to a different slot or PC.
    • Details message: This optional calibration has not been performed.
  • Temperature changes more than ±5°C.
    • Details message: The temperature has changed by more than 5.00 deg C.
  • Elapsed time exceeds 10 of hours.
    • Details message: Elapsed time exceeds 10 hours.
  • External hardware added and enabled in the .
    • Details message: The external input device configuration has changed since calibration.
  • Vertical Calibration is expired or hasn't been performed. Vertical calibration is required before Dark Level Calibration can be performed.
    • Details message: Channel xx Optical Dark Level Calibration for this channel has not been performed since the last Channel xx Vertical Calibration.
  • Power is cycled.

If a message is available, you can return the message by sending the :CALibrate:DARK:CHANnel:STATus:DETails query.

Example Command Sequence

:CALibrate:DARK:CHAN3A:STARt
*OPC?
…  //  Your code to synchronize execution timing.
:CALibrate:CONTinue
*OPC?
…  //  Your code to synchronize execution timing.
:CALibrate:CONTinue