After taking data with HV = OFF and LV = ON, it's clear we have few LTM channels affected by noise coming from LV ( the noise washes out when LV_2.5V = 0). Most of this noise manifests in an overflow of the CTTM scalers ( set now at 700 Hz) and hence they are automatically masked. Unfortunately few of them give an almost low noise ( ~20-30 Hz), and therefore they have to be masked separately.

SItuation on 2009 run:
- CTTM channel 23 , bit 19;
- CTTM channel 33 , bit 5;
- CTTM channel 53 , bit 19;
- CTTM channel 55 , bit 10;
- CTTM channel 70 , bit 5;

SItuation on 2008 run:
Since the addresses of the noisy channels are stable, while waiting for understanding/solving this problem, it looks we have to mask them:

- CTTM channel 16 (SM 8, baby, right), bit 8;
- CTTM channel 17 (SM 8, baby, left), bit 10;
- CTTM channel 33 (SM 16, baby, right), bit 5,6,11;
- CTTM channel 34 (SM 16, baby, left), bit 1,2,20,23;
- CTTM channel 35 (SM 17, baby, right), bit 11;

- CTTM channel 52 (SM 8, back, left), bit 18;
- CTTM channel 68,(SM 16, back, left), bits 12,16;
- CTTM channel 70,(SM17, back, left) bit 5.

Please note:
- this effect comes ONLY from SM 8,16,17.
- the number of masked channels is 14/553 = 2.5 %.

-- EugenioScapparone - 01 Oct 2008