we did some tests with Marie to make some vibrations on the door.
below, I exhibit some pictures of the scope with the accelerometer plugged on it without or with noise...
this level of noise is not able to make the FPC loosing the lock.
even when saturating the noise signal on the accelerometer, the FPC is not loosing the lock all the time.
then, when a day is very windy, it's possible it could have some effect, but for a normal day, it's seems very doubtful that is the reason...
| Ronic Chiche wrote: |
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After this observation, we did a test with Daniele to try to correlate the road traffic in front of the Igloo with the lock losses observed on the FPC.
We didn't see any clear correlation. Cars or buses are not the direct origin of the FPC lock losses... only when some heavy load is hitting the building, we observed a clear correlation.
So, we still observed a lot of FPC lock losses when the day is windy...
One possible cause could be the large door of the igloo (~20 m²) hitting the Igloo when the day is windy.
I installed the accelerometer on the rail on the bottom of the large door to see if there is any correlation.
| Ronic Chiche wrote: |
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At the end of the day, we found out what was the origin of this noise : some road renovation work with jackhammer and road roller just at the entrance of the "Igloo".
this origin was 100% correlated with a large increase of the accelerometer signal.
but we clearly saw that the FPC is much more sensitive than the accelerometer... the signal can have a small increase or just one peak and the cavity lock is lost.
then, we can make the assumption that all the "high frequency noise" which produces some lock losses could come from acoustic noise due to the road traffic or from the equipments in the bunker itself.
| Ronic Chiche wrote: |
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Today, the lock of the FPC was particularly bad (maybe the worst ever seen), with a lot of high frequency noise.
the lock was impossible during several minutes !
we tried to switch off all the equipments of the machine, one by one without any effect on the lock.
at the end, we looked at the accelerometer installed inside the housing to check if there was some correlation.
and for the 1st time we clearly saw a 100% correlation beween the accelerometer signal with a noise oscillating above +/-300mV
but we didn't find the origin of this noise.
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