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Diethard E. C. Moehr, I&S CTF EMC Hardening for apparatus and special product EMC Diethard E. C. Moehr, I&S CTF EMC Hardening for apparatus and special product EMC problems Industrial Solutions and Services Your Success is Our Goal

Aims of EMC Hardening for apparatus and special product EMC Marketing The aim of Aims of EMC Hardening for apparatus and special product EMC Marketing The aim of EMC is to ensure that equipment and systems do not affect their surroundings to more than an acceptable extent and that they themselves can not be affected by interference from their surroundings. I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems - 07. 2003 Folie 2 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Areas-1 EMC Hardening for apparatus and special product EMC Emission Immunity I: MoehrFolienB EMC Areas-1 EMC Hardening for apparatus and special product EMC Emission Immunity I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT EMC problems 07. 2003 Folie 3 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Areas-2 EMC Hardening for apparatus and special product EMC on PCB Level in EMC Areas-2 EMC Hardening for apparatus and special product EMC on PCB Level in complete devices PCB EMC requirement _ EMC requirements for devices I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT EMC problems 07. 2003 Folie 4 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Areas-3 EMC Hardening for apparatus and special product EMC Immunity Emission conducted power EMC Areas-3 EMC Hardening for apparatus and special product EMC Immunity Emission conducted power interconnect mains cable data, signal radiated H-field ESD RFI BURST SURGE IEC 61000 - 4 parts 2 -6 07. 2003 Various 77 A and CISPR standards E-field others I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 5 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC / EMI always requires an emitter (source), a coupling medium and a receptor EMC / EMI always requires an emitter (source), a coupling medium and a receptor (receiver) EMC Hardening for apparatus and special product EMC Coupling mechanism EMI receptors • TV & radio transmitters • Conductive • inductive / capacitive • radiation • computers & peripherals • • • • analog sensors and amplifiers • industrial public control systems • radio & TV receivers • safety equipment • military equipment • humans (biological risks and hazards caused by electromagnetic fields) 07. 2003 Radar, Navigation ITE & telecom equipment local oscillators of receivers power lines switches motors, engine ignition computers and peripherals fluorescent lights electric heaters arc welders diathermy devices natural sources: ESD noise, lightning, galactic noise I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems EMI sources Folie 6 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

Two pulses in time and frequency domain EMC Hardening for apparatus and special product Two pulses in time and frequency domain EMC Hardening for apparatus and special product EMC t 1 > t 2 and tr > tr -20 d. B/ A Dec ade -4 0 d. B /D ec ad e 2 B I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT 1 problems 07. 2003 Folie 7 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

Shielded rooms; e. g. computer centre Problem: Emission Immunity EMC Hardening for apparatus and Shielded rooms; e. g. computer centre Problem: Emission Immunity EMC Hardening for apparatus and special product EMC I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Emission of the computer system 07. 2003 Folie 8 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

Shield Rooms EMC Hardening for apparatus and special product EMC 07. 2003 Transmitter; e. Shield Rooms EMC Hardening for apparatus and special product EMC 07. 2003 Transmitter; e. g. radio, television, intercom I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 9 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMI in a usual small computer system EMC Hardening for apparatus and special product EMI in a usual small computer system EMC Hardening for apparatus and special product EMC Mainframe Workstation RS RE CRT SJ RE INTRA System EMC CE PRINTER RS C C CE CS CS CE CS 07. 2003 CS I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT RS RE problems Folie 10 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

PCB - EMI Emitters & Receptors EMC Hardening for apparatus and special product EMC PCB - EMI Emitters & Receptors EMC Hardening for apparatus and special product EMC • clock oscillators and clock signal lines • analog amplifiers • disc read heads • relays • write / read amplifiers • switched mode power supplies • logic circuits (microprocessor, buffers, drivers) • line drivers • high voltage parts (supplies) • video and deflection amplifiers • all fast data signal lines I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT Receptors • data signal lines problems Emitters 07. 2003 Folie 11 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC shielding EMC Hardening for apparatus and special product EMC complete integral shielding of EMC shielding EMC Hardening for apparatus and special product EMC complete integral shielding of every box and all cables (compartment shielding) F 1 PS F 1 PCB 2 F 3 F 2 F 4 plastic box metal or metalized box Filters shielded cables non shielded cables 07. 2003 F 1 - F 4 PCB 3 PCB 1 I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 12 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

Integral shielding - Compartment shielding EMC Hardening for apparatus and special product EMC disadvantages Integral shielding - Compartment shielding EMC Hardening for apparatus and special product EMC disadvantages • not always possible • each sub-assembly (PCB, cables, connectors) has to be shielded • design problems • does not help against self-jamming • quite expensive advantages • internal shielding is not necessary • design of the complete device (housing cheaper) • cheap solution in the shielded box 07. 2003 • no self-jamming problems between the sub-assemblies I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems disadvantages Folie 13 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB with one PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB with one connector - CASE 1 low frequency logic medium frequency logic high frequency logic connector 07. 2003 Note: Use separate supplies for the logic families I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 14 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB with one PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB with one connector - CASE 2 digital logic interfaces analog logic lines drivers analog signal driver / receivers connector 07. 2003 Note: Prevent supply layer overlaps (V CC / GND) between the analog and digital area. I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 15 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

Principle of a star supply system for PCBs EMC Hardening for apparatus and special Principle of a star supply system for PCBs EMC Hardening for apparatus and special product EMC fast digital circuits analog circuits slow digital circuits interfaces and line driver circuits connector +5 V 07. 2003 OV I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 16 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB with one PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB with one connector - CASE 3 Note: • Use a “star” supply system for VCC / GND. • Prevent loops in VCC / GND. high medium low frequency logic • Prevent loops in clock signal and data lines. • Keep supply voltage paths for drivers short. connector I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems 07. 2003 Folie 17 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

PCB Layout Guidelines EMC Hardening for apparatus and special product EMC Note: • Assign PCB Layout Guidelines EMC Hardening for apparatus and special product EMC Note: • Assign logic (interface logic) to the connectors. • Sort logic according to its purpose. • Separate logic families. • Use separate supply systems. Interface 1 Interface 2 edge connectors connector E 1 connector E 2 I / O circuits for interface 1 high freq. logic medium freq. logic I / O circuits for interface 1 low freq. logic connector M 1 medium freq. logic high freq. logic connector M 2 07. 2003 mother board I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems PCB with several connectors Folie 18 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

Dependence of line impedance on length, width and thickness of the line considering the Dependence of line impedance on length, width and thickness of the line considering the pulse frequency EMC Hardening for apparatus and special product EMC d l b d b l f b = 1 mm = thickness of the line = width of the line = length of the line = frequency d = 0, 03 mm b = 10 mm d = 0, 03 mm b = 3 mm d = 0, 03 mm f 10 30 100 300 10 Hz 6 m 17 m 57 m 100 Hz 6 m 17 m 1 k. Hz 6 m 10 k. Hz l/mm 300 172 m 6 m 19 m 57 m 172 m 6 m 17 m 58 m 100 k. Hz 7 m 24 m 92 m 1 MHz 44 m 173 m 727 m 10 MHz 437 m 1, 72 100 MHz 4, 37 1 GHz Industrial Solutions and Services Your Success is Our Goal 43, 7 l/mm 100 300 57 m 6 m 17 m 19 m 57 m 6 m 174 m 6 m 20 m 61 m 7 m 24 m 311 m 14 m 62 m 225 m 44 m 174 m 2, 6 131 m 590 m 2, 18 440 m 1, 73 7, 25 25, 8 1, 31 5, 89 21, 8 4, 4 17, 3 17, 2 72, 5 258 13, 1 58, 9 218 44 173 172 725 2, 58 k 131 589 2, 18 k 440 1, 73 k Common Technical Functions Folie 19 100 07. 2003 30 I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems

PCB Layout Guidelines EMC Hardening for apparatus and special product EMC • Use different PCB Layout Guidelines EMC Hardening for apparatus and special product EMC • Use different areas for high, medium and low frequency logic. • Use a “star” supply voltage system for V CC and GND. • Use different areas for digital and analog logic. • Assign interface logic to the connectors and keep connection as short as possible. • Avoid parallel trace runs for interface signals and clock signals (cross talk problem). • Consider cross talk between high, medium and low frequency signal lines. I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Summary 07. 2003 Folie 20 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB Multilayer Guidelines PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB Multilayer Guidelines - CASE 1 1 2 IL - Interconnect Layer Advantage • easy to repair IL 1 3 Disadvantage VCC 4 GND 07. 2003 IL 2 • radiated emission from IL located outside of the PCB I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 21 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB Multilayer Guidelines PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB Multilayer Guidelines - CASE 2 1 2 Note: Direction priority in IL 1 and IL 2 to avoid cross talk. VCC 3 IL 1 Advantage • no radiated emission from signal and data lines 4 IL 2 Disadvantages • not easy to repair GND 07. 2003 • problems with very fast signals in the inner layers I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 22 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB Multilayer Guidelines PCB Layout Guidelines EMC Hardening for apparatus and special product EMC PCB Multilayer Guidelines - CASE 3 SH IL IL GND VCC IL IL SH - Ground VCC - Supply Layer 07. 2003 IL - Interconnect Layer GND SH - Shield Layer I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 23 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

PCB Layout Guidelines EMC Hardening for apparatus and special product EMC Location of decoupling PCB Layout Guidelines EMC Hardening for apparatus and special product EMC Location of decoupling capacitances possible solution with low R and L Attn. : multi layer optimal position of DC 07. 2003 decoupling capacitance DC useless due to R and L in the current path I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 24 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

Decoupling capacitances the wrong and the right way EMC Hardening for apparatus and special Decoupling capacitances the wrong and the right way EMC Hardening for apparatus and special product EMC +5 V + IC Decoupling capacitances IC - OV +5 V right short paths connecting the pins minimize L and C 07. 2003 wrong long paths connecting the pins introduce L and C OV I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT IC problems Folie 25 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

 • EMC on PCB’s EMC Hardening for apparatus and special product EMC • • EMC on PCB’s EMC Hardening for apparatus and special product EMC • Generally you should take note of the following: • avoid ground loops on the PCB • avoid VCC loops on the PCB • use a filter to avoid noise from the PCB being reradiated from supply data cables • use completely shielded oscillators only • connect the housing of used oscillators to the 0 volts of the PCB, locate a 0 volt area under oscillators to avoid other wires passing this area • keep all clock traces as short as possible, the faster the signal is the shorter the trace has to be • use decoupling caps for any chip (value 100 n. F) • traces from the decoupling capacitance's to the supply pins of the chips have to be as short as possible I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Part 1 07. 2003 Folie 26 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

 • EMC on PCB’s EMC Hardening for apparatus and special product EMC • • EMC on PCB’s EMC Hardening for apparatus and special product EMC • the faster the logic is the shorter the distance between the supply plug and the fast logic has to be • use a “star” power (VCC / ground) supply, for instance, to separate analog and digital devices • use a separate VCC / ground path for chips known to produce most of the noise • don’t connect 0 volt and the shield • ensure the possibility of placing a capacitor between 0 volts and the shield in case of ESD or radiation problems • if using multi layer PCB’s take care to have shielding layers on the top and on the bottom • put interconnecting layers inside • ensure that the VCC / ground traces are as wide as possible in order to create low HF resistance and inductance 07. 2003 • terminate all inputs of gates to ensure better immunity of the device I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Part 2 Folie 27 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC on PCB’s Part 3 • avoid overshoots on any signal because they produce EMC on PCB’s Part 3 • avoid overshoots on any signal because they produce a broad frequency spectrum problems • ensure that rising and falling slopes of used clocks are as slow as possible • terminate all metal parts of the housing to the shield potential (not to 0 volts) • don’t forget spark over problems caused by ESD discharges from persons and devices touching the surface (pay special attention to LED’s) • use an electrolyte cap. (at least 10 µF) at the point where the supply voltage reaches every PCB (no tantalum cap) • use the slowest system frequency possible • especially for keyboards (and similar units): use the slowest scanning frequency possible • use level dependent interrupters instead of slope dependent interrupts I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT EMC Hardening for apparatus and special product EMC 07. 2003 Folie 28 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC on PCB’s Part 4 • use a watchdog timer for monitoring the system EMC on PCB’s Part 4 • use a watchdog timer for monitoring the system problems • fill unused ROM space with a restart command • be careful with spike dependent units (flip flops and latches), level triggering, if possible I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT EMC Hardening for apparatus and special product EMC 07. 2003 Folie 29 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Complete EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Complete electronic system, e. g. example computer system: I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems 07. 2003 Question: What has to be done to meet the EMC requirements in order to get FCC / CE approval? Folie 30 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Main EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Main questions to be solved: • Which shielding system is necessary (complete or compartment shielding)? • Which filtering is necessary for the mains? • Which cable shielding is necessary for internal system cables? • Which connectors have to be used for internal system cables? • What EMI hardening is necessary for other I/O ports (telephone lines, etc. ) ? • How to keep EMI hardening cheap? I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems 07. 2003 Folie 31 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Choosing EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Choosing a filter by the manufacturer’s data sheet. • filter performance from a manufacturer’s data sheet • attenuation in the required frequency band (10 k. Hz 30 MHz) looks high enough • purchasing dept. orders 1000 filters • filter is installed in the device and the system is taken to the EMI test site for compliance testing and • the system fails the test because the filter does not work as promised Reason: • filters are measured by the manufacturers acc. MIL STD 220 in a 50 / 50 Ohm system (50 Ohm source impedance / 50 Ohm load) • real installation conditions vary widely (for instance for mains filters 1 Ohm / 103 Ohm not unusual) Solution: • check any filter in the real installation condition before ordering I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Situation: 07. 2003 Folie 32 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC What EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC What to do and what not to do in filter mounting: I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems 07. 2003 Folie 33 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC What EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC What to do and what not to at cable entries: I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems 07. 2003 Folie 34 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC The EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC The performance of pigtail connections 1: Example: coaxial cable (braided shield) with two pigtails to connect the shield via a connector pin to GND 07. 2003 2 x 10 cm wire (~4 inches) with 1 µH /m ZT = 10 mohm at 1 MHz 1 m long ZTP = j L = 0, 6 ohm at 1 MHz I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Folie 35 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC The EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC The performance of pigtail connections 2: Conclusion: Voltage drop along the shield for: I = 1 A (Ohm’s law) U = I x (ZT + ZTP ) U = 1 A x (10 -2 + 1, 2 ) = 1, 21 V 120 times the voltage drop as without pigtails. • This shield is not an effective shield. • Transfer impedance of the shield ZT can be as low as possible, according to the pigtails the whole impedance is too high. • Emission and susceptibility problems can be expected. I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems 07. 2003 Folie 36 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Shielded EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Shielded cables and the performance of pigtails: Transfer impedance ZT and shielding effectiveness as of the cable: as =db lg in 20 for our example 50 ZT ZT = 1, 21 as = 32 d. B Good coaxial cables have as 70 d. B ( ZT ≤ 15 m ) Cable manufacturers are able to measure the as and ZT of a cable according to MIL STD 220. I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems 07. 2003 Folie 37 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC • EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC • All metal surfaces which are expected to have a good metal conducting contact to each other have to be protected against corrosion (for instance Sn coating on steel or aluminium surfaces). • Metal or metalized surfaces where contact may arise during operation or normal service of a device should never be floated but connected to GND or safety potential where available. • Connections between metal surfaces have to be solid; no accidental connections allowed; enforced contacts recommended. • Shields of cables have to be connected 360° with metal or metalized connectors. I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Summary 1: 07. 2003 Folie 38 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Summary EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC Summary 2: • Bodies of connectors have to be connected with metal or metalized PCB frame if available; with connections between logic GND and the shield potential take special care. • Main filters have to be connected with the metal or metalized housing of the device at the place of cable entry in a solid way. • Anti-corrosive coatings, paint, Al 2 O 3 and chromate coatings are not conductive even if they sometimes look like metal (remember to be aware of ESD problems). • Moving parts such as doors have to be contacted by finger stock systems every 10 - 20 cm depending on the highest frequency. • Sometimes additional shielding is required for special functional assemblies in the devices (turners, video amplifiers). I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems 07. 2003 Folie 39 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC • EMC Guidelines for complete systems EMC Hardening for apparatus and special product EMC • Radiation sources cannot be placed behind slots for ventilation; also pay attention to signal lines behind slots. • Prevent ESD from sparking directly into PCBs. • In case of a plastic housing connect the shielding of cables also via metal or metalized connectors to metal or metalized PCB frames where available and via these frames to logic ground or better safety ground. • If possible always ensure the separation of logic ground (GND) and safety ground (G/Y wire), only one conductive connection in a complete system is allowed. • Always remember: HF current always takes the path of lowest impedance; this path can often be unusual; in case of different path in parallel the HF current uses only the path with the lowest impedance. I: MoehrFolienB 15 -15_Des_Argentina_03_Logo_03 -07. PPT problems Summary 3: 07. 2003 Folie 40 Industrial Solutions and Services Your Success is Our Goal Common Technical Functions

Contact: Diethard Moehr I&S CTF EMC Schuhstraße 60 D-91052 Erlangen Thank you very much Contact: Diethard Moehr I&S CTF EMC Schuhstraße 60 D-91052 Erlangen Thank you very much for your attention. Industrial Solutions and Services Your Success is Our Goal Phone: Mail: +49 (9131) 7 -27210 diethard. [email protected] com