EMC of instrumentations systems

Program

1 - Introduction

• What is EMC?

• Representation of a sinusoidal and trapezoidal signal

• Time-frequency relationship

• Definition and characteristics of an electromagnetic wave

• Relationships between conduction and radiation

• Use of decibels

• Common mode/differential mode

• Low/high frequency limit

• Envelope detection

• Digital circuit interference



2 - The 6 types of coupling

• Ground coupling

• Conductor impedance

• Capacitive coupling between board and ground

• Electrostatic shield

• Crosstalk coupling

• Magnetic field coupling

• Loop voltages

• Electric field coupling

• Metal plane shielding



3 – Earth and ground

• Definitions of earth and ground

• Role of the earth network

• Earth resistance

• Safety conductors

• Ground network

• Equipotentiality and EMC

• Ground loops and between grounds

• Problems with star grounding

• Ground meshing



4 – LF disturbance sources

• The 4 low-voltage neutral schemes

• Orders of magnitude of currents in grounds

• Sources of 50 Hz magnetic fields

• Radiation from a transformer

• Sources of 50 Hz electric fields

• Effects of lightning on equipment



5 – HF disturbance sources

• Radiation from radio transmitters

• HF industrial equipment

• Switching converters

• Variable speed drives

• Dry contact bounce



6 – Low frequency protection

• Common mode rejection by isolation

• Symmetrical differential connection

• Equipment with guard in noisy environment

• Isolation transformer

• Optocouplers

• Effect of a filter on a pulse

• Surge arresters

• Necessity of surge arresters

• Choice of surge arrester type

• Examples of surge arresters

• Implementation of surge arresters



7 – Filtering of HF disturbances

• Different types of filters

• Different low-pass filter diagrams

• Use of ferrite cores

• Common mode choke

• Mains filters

• Rules for installing a mains filter

• HF filtering of signals



8 – Shielded cables

• Transfer impedance

• Principle of the reducing effect

• Measuring the reducing effect

• Connecting shielded cables

• Special case of low-frequency common mode

• Over-shielding

• Reducing effect of cable trays

• Connecting cable trays

• Wiring very low-level sensors

• Thermocouples

• Connecting shielded connectors

• Signal classification

• Wiring rules



9 – Electrical and EMC measurements

• Resistance measurement

• Characteristic impedance of a line

• Measurement of the characteristic impedance of a line

• Losses in coaxial cables

• Passive oscilloscope probe

• Active voltage probes

• Measurement of common mode voltages between grounds

• Construction of an HF current clamp

• Conducted immunity test on site