INFICON Spot CDS550D - Manual (Page 10)

Research & Development
SPOT CDS500D & CDS550D OEM Sensor SPI-Interface Specification_V1.1 Page 10 of 14
Christian Berg, T based on Felix Mullis, TL Created 11/10/2014 2:36:00 PM
5 Appendix
5.1 Grounding Concepts
Situation
• high impedance (> 100kOhm) between sensor elec-
tronics and
– housing
• very sensitive measurement frontend (resolution is
fF)
• shielding against noise necessary
• the metallic case of the sensor must be electrically
connected to the power supply reference terminal
(GND) of the driving electronics
Concept #1
• “indirect” connection via earth lines
• easy to implement
• keep impedance of earth connections as low as pos-
sible
Concept #2
• direct connection which may optionally be connected
to earth
• more laborious to implement
• „direct“ connection better shielding possible