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EMC Monitoring:Hardware descrition



Underlying Hardware
The EMC monitoring is based on the GeneralMonitoring Board (GMB). It's 32 inputs can be configured to accept
4-20 mA signals as well as voltages. It can therefore be used to convert signals from Temperature sensors, Humidity sensors, Oxygen cells, Currents, Voltages, etc... The table below gives the channel assignment for gmb type used by the EMC.
 
 
 
Channel 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Crystal Temperature T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T
Low Voltage NU NU T T T T T T T T T T I V I I I V I I I V I I I V I I I V I I
Nitrogen
Flow
I I NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU NU

The converted signal from each channel is sent periodically to a central monitoring program based on EPICS. To achieve this, the central CPU running the monitoring program is connected to every GMB via CAN bus. In the EMC we have 4 independent CAN buses. This CPU is called IOC (Input Output Controller and resides in a crate B620B-03 in the electronics house. The 4 CAN buses are organized this way:
 

CAN Bus number
Detector Partition
Hardware connected
CAN0
Barrel Backward
Crystals,IOB,ADB,FSAR,RadFet
CAN1
Barrel Forward
IOB,ADB
CAN2
End Cap
IOB,ADB,Crystals,RadFet,TRB,NeutronSource
CAN3
General
Light Pulser,Chillers(soon)

The GMB need to have two separate powers: +5V is required by the CAN bus interface in order to drive the bus.
A the moment all monitoring boards on the detector get their 5v via an independant power supply in the back of rack B620B-03. All the monitoring boards in the Electronics house (IOB monitoring) get their 5V via the CAN bus cable through pin 6 and 9 on the connector. The power source being the VME crate power. No adjustments to this power line can be made and therefore long haul cables with significant voltage drop can't be hooked to this power line. That's why we have separate CAN bus power supply for all the boards on detector.
The other power source need by a GMB is 12V. It is used to power the micro controller, ADC and multiplexer used to convert the input signals. The 12V input is the little black molex connector on the front of the GMB(see picture). Here are drawings of the boards location on Barrel Backward, Barrel Forward,End Cap, Electrnics House Rack 1,ElectronicsHouse Rack 2, Electronics House Rack 3 Here are some pictures of the back of the electronics house crates to illustrate the layout of the cables. The first picture shows the power distribution rail used to fanout the GMB power to the electronics house GMBs. There's one such Din Rail per rack.


The second picture shows the connection of the CAN bus cables to the interface card on the back of rack B620B-04. From the Interface board, the CAN bus signal is transported to the front of the rack via flat ribbon cables and is fed to the CAN interface shown on picture 3.

You can see on this picture the 4 CAN interface modules with their flat ribbon cable connecting to the CAN bus. The green led are flashing when there is traffic on the bus. Whe the IOC is rebooted, the lights will stop flashing and resume when the reboot is complete.

GMB picture. The 32 inputs are on the back of the board. CAN bus connectors are on the front (black connectors)

GMB picture.


Mark Freytag is the person to talk to in case you need to get a board fixed or tested. He is also able to make new spare boards for you if you need any. Here are the resistor/capacitor values for the configuration of the sensor input.
  • The input configuration for the Temperature Board is 32 channels of current monitoring (AD592) with :
    RL: 10K
    RS: 0
    Cap nothing
  • And for Low voltage we have 2 Low voltage channels (unused), 10 channels with current monitoring (AD592):
    RL: 10K
    RS: 0
    Cap nothing
    and 20 channels of voltage monitoring:
    R10: 100K
    R11: 0
    Cap nothing.
That's what I have picked up from one of the configured boards The jumper setting is described in the gmb babar note.
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Last modified P-A Fischer  January 11 2000