Electromagnetic compatibility (EMC) is a branch of electronics related to identifying and solving problems caused by electromagnetic interference (EMI) between devices. It encompasses both attempting to prevent unwanted emissions from a device and also ensuring that emissions from another device ...

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How to read noise suppression sheet specs?

I am trying to shield a component from GSM850 and GSM900 radiation. When I read the datasheet below, I don't quite understand which parameters I should care most (relative permeability, magnetic ...
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34 views

How to read EMI absorber specs?

I am looking for some EMI absorber to shield a component from GSM 850/900 radiation. Never use one before. From p.2 for the datasheet below, the AB7050 absorber has ~-3.5dB reflection loss and ~80% ...
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1answer
57 views

How can 50MHz noise impacts WIFI sensitivity?

From the Murata website (http://www.murata.com/en-us/products/emc/emifil/casestudy/solution/wlan), it mentions "it is the higher harmonic waves of the CLK signal (50 MHz) transmitted to the Wi-Fi ...
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43 views

PCB layout for filtering an input signal external to chassis

I read this Murata Know-How presentation on PCB layout for a filter for an input signal. Judging by this picture, do I have to make a separate polygon GND for filter output? And connect this polygon ...
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1answer
69 views

Help on defining the 8-layer stack-up for a high speed design

In many of the PCBs of my company we have done the stack-up as following: (stack-up A) Pads/GND/Some LF signals Signal1 Signal2 GND plane PWR planes (more than one due to several secondary supplies ...
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37 views

Help with deciding my layout for EMC tests and SI. Different alternatives.

I am thinking what way would be the best to layout my system in order for it to have the best SI and pass EMC tests. My system consists in two PCBs joint by a flat flex cable (up to 7cm) and these are ...
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50 views

Can WIFI PIFA Antenna pick up GSM signal over the air and radiate 900MHz harmonics?

My device supports 3G and WIFI (2.4 and 5G). The WIFI PIFA antenna is radiating 900MHz harmonics (1800 and 2700MHz) when cell modem is transmitting. After I removed the WIFI ant, noise disappeared. ...
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49 views

Should I let my microprocessor and sensors have floating ground?

For my home automation project, I'll be controlling about 10 mechanical relays, and 5 mosfet switches, ALL OPTICALLY ISOLATED. relays/switches will be controlled by Beaglebone Black(BBB), a 3.3V ...
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2answers
67 views

AC signal and ground plane with another trace passing between - is this bad?

In learning about reducing a circuit's EMI emissions, I've learned the importance of a ground plane, in that it allows the current-return for an AC signal in an adjacent layer to flow directly under ...
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1answer
45 views

What functions do EMC filters in variable frequency drives serve?

Most VFDs I've seen have EMC filters in them, though in many cases they're optional or can be disabled by the user. Exactly what function do these filters perform? What problem are they intended to ...
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43 views

protection device on power line and io lines

I have seen many design to protect nput circuitry from surge , EFT and ESD Mov's for surge protection, Choke for Conducted emission TVS for ESD. still i am confused on below point Q1) If surge is ...
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81 views

How often does EMC certification have to be repeated (especially in Australia)?

I realise that this may be largely legal in nature and may be off topic, but I think that the users of this site are most likely to be able to answer accurately, so I shall ask and risk being shot ...
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1answer
57 views

Common mode inductors with high pulsed current

I have an application where I am producing fairly high short duration pulses into a load, 50A and 100us. I am looking for a common mode inductor to help reduce my EMC emissions. Because these pulses ...
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1answer
61 views

Varistors set to ground or case by isolated ground/case

I have a isolated ground from the case in my device. The Supply Voltage is +24VDC with Ground and separated CASE, so no safety issues. On any signals coming from the case (Plugs) I put varistors, but ...
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1answer
51 views

Where can I find test labs for FCC and other unintended radio emissions testing? [closed]

Where can I find labs where I can pre-test or certify an electronic product intended for sale, according to FCC rules? I've searched the FCC website for a list of certified labs, without finding such ...
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1answer
66 views

Maximum Allowed inrush current in Eurpoe

Context: I am designing an device that is placed between the main AC network (230V 50Hz) and some consumer devices (PC, TV, etc..). My device is measuring the current drawn by the consumer device, we ...
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2answers
64 views

How to add/sum field strengths given in dBuV/m?

I'm trying to theoretically analyze the resulting field strength, R, from two devices with given field strengths (say r0 and r1), both represented in dBuV/m. My first intuition was to use R = 20*log(...
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1answer
223 views

Making aluminium conductive for an RF shield enclosure

I'm not sure if it's appropriate to ask here, but I would assume many people in electronics would have experience with this. I'm enclosing an RF sensitive PCB into an sealed aluminium enclosure. ...
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49 views

Dimming LED lights with PWM, driver quite far from LEDs, noise considerations

There were a few questions like this before, however I haven't found ultimate answer yet. I'm going to drive LED lights in my house with multi-channel driver (PWM controller + MOSFET Transistors), ...
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71 views

Basic surge and overvoltage protection

My requirements are: protect the device from surges according to IEC 61000-4-5 Class 2 protect from 400VAC long term overvoltage (working voltage is 220VAC-15%...230VAC+10%) IEC 61000-4-5 Class 2: ...
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1answer
65 views

FCC-approval and “modular” integration

I see that a PCB requires certification even if it incorporates a certified RF module, so EMC tests for spurious emissions will still be needed. Is FCC-approval needed if a Raspberry Pi is shipped/...
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2answers
81 views

Kick-off Spread Spectrum Clocking

Need of SSC: Spread spectrum clocking (SSC) is a special way to reduce the radiated emissions of digital clock signals. These levels or energy is radiated and therefore this is where a potential EMI ...
4
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1answer
169 views

Will FCC EMC tests need to be redone?

In light of the new FCC rules that Chinese (and all non-MRA) labs will no longer recognised in July and all EMC tests need to be done at FCC-authorized Telecommunications Certification Bodies, for FCC ...
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3answers
77 views

Changing the value of capacitor

What is the effects of replacing signed capacitors with 4uF ones related to Emi Filter performance (Electromagnetic compatibility issues). We observed that the time with 4uF ones keeps longer (power ...
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1answer
95 views

20H rule EMI/EMC effectiveness

I have been doing some research into the effectiveness of applying the 20H rule to 4 layer PCB designs and have been finding some very conflicting information. Some sources (including a few IEEE ...
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1answer
149 views

Transient protection to prevent microcontroller freeze - Selecting MOVs and TVS diodes

I have a circuit which contains an offline switching SMPS circuit (based on viper22a) converting 220V to 5V regulated down to 3.3V using linear regulator IC. This powers up an ESP wifi module and ...
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42 views

TRIAC Circuit triggered due to interference

I have a small circuit designed to switch on the lights in my room using a wifi-enabled microcontroller Particle Photon. The circuit is based on an opto-triac and TRIAC setup where the microcontroller ...
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1answer
83 views

How to protect IC for VCC surge?

I have on my circuit an integrated circuit (IC) that has been destroyed by some event. After the event, the component's Vcc pin was shorted to GND inside the IC. After measurement, it appears that ...
2
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2answers
320 views

DIY ESD generator (ESD-gun)

Does anyone have a simple ESD generator circuit for pre-compliance testing (3KV-20KV)? e.g. can it be built from the following? http://www.ebay.com/itm/New-High-Quality-3V-to-7KV-Boost-Step-up-Module-...
2
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1answer
237 views

Spikes induced on PCB. EMC problem?

I designed the following PCB, where after testing a faced a severe (EMC related?) problem. This board houses an STM32F103 developing board. On the right of the PCB, there are 6 thermistors connected ...
5
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1answer
160 views

How can I observe rectifier switching noise?

I understand there is such a thing as rectifier switching noise. I would like to observe it on the bench, but I don't understand its causes well enough to design a test setup. Once in hand, I'd like ...
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2answers
52 views

Switcher discontinuous mode - potential EMI problem

I need to design switching mode power supply with input voltage range of 25V-45V and output voltage 5V@2A. Power supply must be ON while the system is in sleep mode(~1mA consumption). In that ...
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1answer
1k views

What does the Y capacitor in a SMPS do?

It seems that a well-designed SMPS has a capacitor connecting the ground planes of the primary and secondary sides of the transformer, such as the C13 capacitor here. What is the purpose of this ...
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2answers
451 views

How to measure EMI without special equipment?

I have bought a cheap dashcam to play with, only to discover that my GPS receiver stops working when it's on. After I ruled out power supply issues (both devices have batteries), I'm left with a ...
3
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1answer
90 views

Blocking RF on same side as PCB antenna?

I have a penta-band GSM transciever on a 4-layer board, along with a matched chip antenna. Similar concept to EE.SX/questions/35836/how-do-components-on-a-ground-plane-of-monopole-pcb-antenna-effect-...
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2answers
83 views

Will EMI strongly affect my sensor reading

I'm using an Arduino to read analog values from my sensor running at 5V using a voltage divider. The sensor contains a force resistive sheet where the resistance of the sheet decreases as force is ...
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1answer
57 views

Alternative Gigabit Ethernet Connector - considerations for impedance, signal integrity, and EMC considerations?

I have a design that does not have enough vertical clearance for a standard RJ45 socket. I'm hoping to use a connector like this one from Molex. I will use Cat5e cable when building my cable with the ...
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1answer
39 views

WIre length in Conducted emission test

What should be the Minimum or maximum input power cable length can be used in Conducted emission test. Length from EUT(DUT) to LISN. What if my product come with input cable length out of MAX limit.
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2answers
47 views

Transceiver and RF Emissions (Unintentional)

My question is simply what is RF emissions (unintentional) and how does it relate to a device (such as a smart phone) which contains a transceiver or transmitter (baseband IC) ? Which part of a RF ...
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1answer
58 views

Expanded standard deviation in logarithmic scale [closed]

Hello and good day to all. Referring to picture attached I have a question. . I am working on different measurements and trying to find the mean and standard deviation values of these measurements....
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2answers
83 views

12V vs 5V servo

I am looking to actuate a throttle on an internal combustion engine. I am using a 5V servo driven by an Arduino Mega2560 at the moment. The throttle is very close to the engines alternator and there ...
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2answers
79 views

Avoid EMI in power circuit controled by MCUs

This is a toy project just for fun. As anybody knows, if I want to control a lamp by a simple switch, the circuit is as follows: However, I want to change the circuit so I can control a lamp with ...
3
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3answers
804 views

EMC testing vs. EMI testing

What is the difference between EMC testing (Electromagnetic compatibility) and EMI testing (Electromagnetic interference)
4
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1answer
178 views

Are these EMI noises?

I have always heard about EMI noises but have not really meet them or measured them. Our system composes a MCU running at 168MHz and a 16-bit DAC which is supposed to provide high-precision voltages ...
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0answers
47 views

Image current and return current

I find I'm a little confused about "image current" and "return current" in PCB/EMI/EMC design. Are they equivalent? Many docs use this model when talking return current Exactly, I will treat the ...
3
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2answers
137 views

Ribbon Cable Noise Susceptibility

As part of a product upgrade we are looking at replacing looms of wires bound together by cable ties or spiral wrap with ribbon cable. We are doing this to try and cut cost and assembly times. We are ...
1
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2answers
182 views

Signal and power integrity - 4 layer board

Let's assume that we need to design Mixed signal PCB with 2 fast integrated circuits(tr_min = 1ns) operating at different voltage levels(3.3V and 4V). There are however other voltage levels on the PCB(...
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27 views

Electric Vehicle Temperature Monitoring

I'm looking to implement a system to monitor the cell temperatures of about 80 cells in a 240-cell battery pack for an electric vehicle (yes, at least 80 cells must be monitored). I'm looking for a ...
3
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3answers
212 views

What is the thought process for specifying an EMI bypass cap on line transformer secondary?

Update It turns out I had mistakenly interpreted the role of the capacitor in question here as an EMI filter for line noise. It looks like a capacitor in that position actually serves as a snubber ...
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57 views

Is 'RFI' a term in active usage, or is it all 'EMI' now?

I'm studying capacitors in some detail just now, and one of their typical uses, of course, is to bypass high frequency interference at sensitive circuit inputs. I want to get my terms straight, and ...