I need to get these readings: ITU BS-1770 with a loudness measurement that does not exceed -24 dB with all channels measured for the length of the programme material. How do I get started?
The two descriptors in LM5D ("Consistency" and "Center of Gravity") always measure based on ITU-R BS.1770-1. They also don't change, regardless of Pref settings.
You should measure the programme material from start to finish and note the value of Center of Gravity. If, for instance, this is -22.7 (LKFS), and the Target is -24.0 (LKS), a gain factor of -1.3 dB should be applied.
To have the Radar and Momentary loudness (outer ring) aligned with a Target loudness of -24.0 LKFS, the Pref parameter "0 LU Equals" should be set to "-24 LFS". This setting puts -24 LKFS at the 12 o'clock position of the outer ring (Momentary loudness) as well as at the second circle of the radar (the bolder one).
Again, this will not change the numerical readout, but would help an engineer doing live balancing to center production around -24 LKFS.