1. Status LSM compass board
Daan van Eijk
Calibration meeting
July

2. The LSM303D LSM AHRS-LNS Price Bare: €3 On PCB board: €13
LSM has two sensors:
Accelerometer (g_x, g_y, g_z)
Magnetometer (b_x, b_y, b_z)
LSM
AHRS-LNS
Price
Bare: €3
On PCB board: €13
Indication: €50-60 (?)
Power consumption
1 mW
400 mW

3. LSM axes Y X Z Y X Z Y X Z
Cross: into paper
Dot: out of paper

4. PMT pointing wrt LSM axesY X Z Y X Z
PMT 0 is in -x direction
PMT 9 is in x direction
Pressure gauge and PMT 6 are in –y direction
PMT 1 is in y direction

5. LSM axes wrt outside of domY X Z X Y Z

6. Definitions…
For all definitions and calculations, I have been using NXP Freescale Semiconductor Application Notes: AN3461, AN4248, AN4246 Y X Z
Rotate to actual mounting in DOM
DOM pointing direction

7. Calculating yaw, pitch, roll
From: AN4248
(vx,vy,vz) is the hard-iron offset vector

8. But…
From: AN4248
Rotate to DOM orientation
Y_LSM = - X_DOM
X_LSM = Y_DOM
Z_LSM = Z_DOM
+yaw
+pitch
+roll
KM3NeT has its own definitions of yaw, pitch and roll (see KM3NeT_DET_2014_002-PMT_map_v5)
They are all opposite in direction to AN4248:
Yaw, pitch and roll all get a minus-sign with respect to previous slide:

9. LSM in DOM164 (for APC water tank)
Rotation of the DOM in xy-plane to calibrate LSM
The LSM systematically yields an ellipse (also on naked CLBs)
Soft iron correction is needed to scale the magnetometer data (see plots)

10. Acceptance test DOM164 with lsm
DOM y-axis pointing to geographical South: yaw = 180
Perform the same operations for all future raw data
Calculate yaw, pitch, roll from calibration-corrected raw data
DOM acceptance test passed!

11. What else?
What else does the Calibration Group want to qualify on/with the LSM?
Full x,y,z soft-calibration?
Ellipsoid fit, fit parameters yield the soft-iron matrix W
Any experience?
Calibration on naked CLBs or on DOMs?
DOMs: xy is easy, other axes are more complicated
How different is the (magnetic) situation once deployed?
Could we calibrate all compasses by taking data while unfurling a DU?
Manpower?

12. CLB FW/SW developments
Data read by CLB from LSM is truly raw sensor data
Only a conversion from 16-bit int to floating point
This is different from AHRS, where there’s pre-processing on the AHRS chip, depending on the AHRS FW version
See questions section
Vincent has prepared a CLB SW/FW version that auto-detects the LSM or the AHRS. Can be released any moment.

13. Other Questions (on AHRS-LNS compasses)
Do we know which DOM carries which AHRS FW?
How is this ‘recognized’ in data-taking?
Does ‘raw data’ mean the same in all AHRS FW versions?
If different (I sincerely hope not, see previous question…), how is this taken care of in all offline yaw, pitch, roll calculations?