Far Detector Grounding
- Proposal for Far
- Details of MUX Box electrical isolation
Near Detector grounding
No documentation, but the Alner phototube boxes
do not need to be isolated in the manner which the Far MUX boxes do
Slides on DAQ
grounding from the DAQ Review, July 2000; 5 pages, PDF format
DAQ Grounding Summary - July 2000
The FEE is not foreseen to be adversely effected
by the DAQ system, in particular by the DAQ components in the readout crate.
The PVIC inter-crate connection system has been specifically designed for
applications like the one used in the MINOS readout and by careful attention to
other subsystems in the readout crate any risk of creating ground loops or
noise injections can be minimised.
- DAQ system components which may
effect the FEE
The only DAQ system components which are close to the
Front End Electronics are the ROP (6U VME Readout Processor) and the PVIC (6U
carrier and 2 mezzanine cards plugged on this card). These two cards are
"joined together" by a side connector which joins the two cards together
(through PCI bus) and for our purposes can be viewed as one unit.
and PVIC together have the following external connections:
- LV power (+5v) and ground connections to the crate
- Ethernet port (10 base-T).
- Two RS232 connections - one to a closeby converter
(RS232 to Ethernet) and another to the Timing Receiver Card which is situated
inside the readout crate.
- Electrical PVIC (shielded differential PECL multi-core
cable which is being connected to three other neighbouring crates).
- Optical PVIC connection to the Farm.
- Differentiation between Shield and
The front panel of the ROP (RIO2 VME processor and
PVIC) modules is separated from the Low Voltage ground by a 'jumper and two
resistors in series' connection. In other words the front panel ground can be
entirely isolated from the LV (logical ground) by removing this jumper. However
the front panels of all the VME cards in the readout crate will be connected to
the crate chassis which is connected to the ac ground (earthed) as a safety
measure. Provided the earthing is done well in the power distribution to all
the crates there should be no adverse effects to the LV grounds when these four
crates are connected together through the cable shields.
- Other system
The front panels of the other cards in the readout
crate namely the VARC and TRC should also be isolated from the LV grounds so
that there are no adverse effects.
- Full Optical
It should be noted that a possible (but not yet
proven) second option being considered is to replace all electrical PVIC
connections with optical ones. Until this is proven it remains only a
possibility but we are actively investigating such an option.