How to run LDD Calibrate

ldd calibrate is an NVS firmware command.
It invokes an internal calibration procedure that obtains a set of six current sample readings and their corresponding power values (measured by the BBS sensor).
It can be run in the field for troubleshooting and maintenance.

Run LDD Calibrate:

When you suspect or when you have beam balance problems, due to low value read by the beam position sensor. Expect to see the following errors:
- LDD: The laser beam was not detected, error [02306]
- [02306] Laser Diode: The mode / state of the beam-pointing is invalid
- [02317] The laser beam was not detected during initialization
When troubleshooting write laser problems.
As part of preventative maintenance.

Tips:

LDD calibrate must be done with a balanced beam.
If the beam cannot be balanced, then try LDD calibrate in order to get the laser startup sequence to work.
Once the laser has balanced, then try LDD calibrate again

Type the following commands:
>> Redirect enable TH2 > eng TH2 > set ldd
Record the two values under LDD currentfactor. Refer to the sample code.
Type the following commands:
TH2 > bpd mode on TH2 > lvd mode local TH2 > ldd calibrate
You will see the following:
Turn on the laser (Y/N)? y Y-Intercept=5.9254 Amps, Slope=1.815 Amps/Watt *** Command Success *** The beam-pointing has settled!
DANGER: The laser is on. Follow all laser safety procedures.
Type the following commands:
TH2 > ldd mode off TH2 > ldd info DANGER: The laser is still on at this point. Remember to turn it off.
Record the active value for the parameter LDD currentfactor.

For full details on how LDD calibrate works, refer to Th2 Write Laser and LDD Calibrate: Details and Troubleshooting (PowerPoint presentation).

Contact Doug Jeffery if you have any questions.