EMC of physical measurements

Goals

formation-objectifs-seointro EMC of physical measurements :

The aim of this training course is to:
- Be able to identify and understand EMC couplings
- Be able to identify sources of interference
- Be able to apply low-frequency protection methods
- Be able to apply high-frequency protection methods
- Know how to adapt EMC investigation measurement methods on site

Program

1/ Introduction

• Roles of Earth


• Earth, mass and 0 V


• Environment classes


• Common mode and differential mode


• Order of magnitude of disturbances


• S/B ratio and immunity margin


• Envelope detection

2/ The 6 types of coupling Coupling via common impedance Impedance of conductors

• Star grounding problem


• 0 V chain


• Coupling between the board and ground


• Capacitive coupling


• Couplings by crosstalk


• Loop field’ coupling


• Wire field’ coupling

3/ LF disturbances

• The four neutral diagrams


• Order of magnitude of currents in grounding systems


• The danger of separated earths


• Sources of 50 Hz magnetic fields


• Sources of 50 Hz electric fields

4/ HF disturbances

• Radiation from radio transmitters


• Switching conversion


• Variable speed drives


• Bouncing of dry contacts


• Losses in cables

5/ Grounding networks

• Definition and effects of ground loops


• Definition and effects of loops between grounds


• Loops in modern systems Impedance of a mesh Mesh by batchesLots


• Connection between racks


• Examples of meshes

6/ LF protection

•  LF common mode protection


• CM rejection by isolation


• Common mode reduction by isolated device


• Device " guarded‘ in the laboratory


• ’Guarded" device in a noisy environment


• BF CM rejection by isolation


• BF CM rejection by symmetrical connection


• Typical asymmetry of a pair


• Filtering of sensors/power supplies


• Amplitude and phase of a low-pass RC


• Asymmetry of input filters


• Characteristics of isolation components


• Effect of a low-pass filter on a pulse


• Main surge arresters


• Surge protection


• Installation of energy/telecom surge arresters

7/ HF interference filtering

• The three methods of MC HF protection


• Out-of-band rejection at the input


• Capacitive filtering of inputs/outputs


• I/O filtering: Errors to avoid


• Common mode chokes


• Impedance depending on the number of turns


• Recommended mains filters


• The three rules for installing mains filters

8/ Shielded cables

• Principle of the reducing effect


• Simple measurement of a reducing effect


• Reducing effect of a cable path


• Connection of cable screens


• Wiring of low-level sensors


• Termination of shielding


• Signal classification


• Wiring and installation rules


• Electrostatic screens


• Choice of connectors

9/ Electrical measurements and EMC

• Methods for measuring resistance


• Characteristic lines and impedances


• Practical measurement of line impedance


• Measurements and coaxial cables


• Rise time correction


• Passive oscilloscope probe


• Use of active voltage probes


• Measuring ground noise: precautions


• Measuring DC voltage between grounds


• Tolerable noise between equipment


• Measuring a sine wave signal in the presence of noise


• TER/S: On-site injection method

10/ EMC remedies

• Electrostatic screens for cables


• Amplifying at the source can be harmful!


• Spectral density of a pulse and use


• Example of sensitive cohabitation/disturbance


• Sensitive cohabitation/disturbance: solution


• Shielded enclosure


• Wiring of a cabinet


• Connections on a bay TRP


• EMC correction method on site


• Méthode de correction CEM sur site