Transcript Introduction

PACS IIDR
01/02 Mar 2001
Grounding Scheme and EMC
Matthias Rumitz, MPE
PACS Grounding Scheme and EMC
1
PACS IIDR
01/02 Mar 2001
Overview
• System Diagram
• Grounding / EMC Concept
• Mechanism Grounding Concept
• Detector Grounding Concept
• Example: MEC Grounding
• Grounding / EMC Status
PACS Grounding Scheme and EMC
2
PACS IIDR
01/02 Mar 2001
System Diagram
FPU
CREs
LCL
Grating
OBC
SPU
CDMU
S/C
MEC
DEC
DPU
BOLC
CDMU
OBC
LCL
PACS Grounding Scheme and EMC
Filters
SPU
MEC
DEC
BOLA
Bolos
Temp.
Sensors
Chopper
Black
Bodies
3
PACS IIDR
01/02 Mar 2001
Grounding / EMC Concept
• Requirements of IID-A (5.10 & 5.14) implemented
• “Distributed Single Point Grounding”
• DPU, SPU, MEC: secondary ground connected to S/C
• Additional EMC measures (DEC, BOLC):
Isolation between primary and secondary power
Reduced slope of DC/DC transformer
EMI filter at DC/DC secondary side
PACS Grounding Scheme and EMC
4
PACS IIDR
01/02 Mar 2001
Mechanism Grounding Concept
• FPU (i.e. mechanisms):
electrically connected to S/C = reference ground
• Drive circuits:
differential supply voltages
• Sensors:
differential read-out
=> no ground loops, EMI risk minimized
PACS Grounding Scheme and EMC
5
PACS IIDR
01/02 Mar 2001
Detector Grounding Concept
• FPU (i.e. detector-housing):
electrically connected to S/C => reference ground
• Warm Electronics (DEC1, DEC2, BOLC):
secondary ground can be connected to S/C
• Detectors (CREs, bolometers):
analog ground can be connected to FPU (= S/C)
=> reference ground:
either Detectors or Warm Electronics
PACS Grounding Scheme and EMC
6
PACS IIDR
01/02 Mar 2001
Example: MEC Grounding
• Outer shield connected
to boxes via backshells
DPU
BOLC
MEC1
1355
1355
SPU
Sync
1355
• Grounding:
DPU, SPU, MEC: local
FPU
1355
Mechanisms Control
Tsens1
Tsens2
BOLC, DEC: local / FPU
Tsens3
Vsens
MUX
&
A/D
Temperature Sensors
Isens
SYNCsens
• Power supplies:
Blue / Red
DEC
1355
DPU, SPU, MEC, BOLC
• Warm Interconnecting
Harness shorter than 1m
Sync
S/C
28V nominal
(redundant)
Filter
Filter
28V
from
MEC1
R/C
DC/DC nominal
DC/DC redundant
R/C
D
C
/
D
C
MEC1-PSU
PACS Grounding Scheme and EMC
7
PACS IIDR
01/02 Mar 2001
Grounding / EMC Status
Component
Grounding
Connectors
Shielding
DPU

SPU

MEC/DEC

BOLC/BOLA

Pinout
Wires









FPU

CRE



Harness



PACS



PACS Grounding Scheme and EMC
EMC
Analysis

8
PACS IIDR
PACS Grounding Scheme and EMC
01/02 Mar 2001
9