Questions tagged [emc]

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 will not cause spurious operation.

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2answers
160 views

How to connect a switch to a microcontroller in an extremly noisy environment

I'm currently working on redesigning the control circuit of a CNC machine (more specific: an Isel milling cutter). Only the digital part will be of interest, I'll keep the old power electronics (motor ...
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1answer
380 views

Converting dBuA to dBuV at 3m and 10m

I'm looking for some advice on converting from dBuA/m to dBuV/m at 10m. I'm trying to convert 10dBuA/m @ 10m. I'm struggling with the uA to uV conversion at distance and can't find online tools to do ...
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1answer
161 views

Problem while simulating EMI Filter for power lines

I was designing an EMI Filter for the CE102 standard. I was a bit confused on how to provide noise source to the circuit, since (as of my knowledge) EMI noise enters our system by parasitic ...
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3answers
891 views

Help Identifying/Decoding Ceramic Capacitor

I am having a difficult time identifying a high voltage, ceramic capacitor that I need to replace. I've tried at length to research this myself to no avail. I am hoping that someone out there can help ...
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1answer
652 views

How do I specify a low RFI LED driver?

I bought a bunch of very cheap 18W LED lamps. I love them; they look great and the light is excellent, however the drivers throw out a lot of RFI and is interfering with my radio (quite bad at 50MHz, ...
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2answers
190 views

SPI, RS232 and DMX-512 data signals beneath the ESP8266-WROOM-02 Wifi antenna

I am working on DMX-512 Controller, which will accept commands for driving Addressable LED strip (GE60RGBW8812A) via ESP-WROOM-02 Wifi Controller and I have several data lines (...
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3answers
355 views

EMC Testing, Radiated Emissions

I recently had one of my new rechargeable Lithium Ion products tested (RE pre-compliance scan) and I had a few frequencies (around 150 MHz) pop (7-10 dBuV/m) above the FCC and CISPR limits. I'm not ...
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0answers
527 views

In LTspice can I convert the units of an FFT which by default seem to be shown in dBV to dBµV?

In LTspice can I convert the units of an FFT which by default seem to be shown in dBV to dBµV? Cause of reason: The reason for this is that I've a modeled a LISN in LTspice where I want to simulate ...
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1answer
175 views

Need help to newbie to understand MIL-STD-461 [closed]

why only 10khz-10Mhz is used for CE102 test ? why not other frequency range is used for CE102 test ?
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2answers
105 views

What could cause impulse noise on switch closure

I have a simple SPST NO Tact switch which is creating a noise pulse in a very sensitive receiver. Moving the switch, shielding etc is not possible. I need to understand how the switch is creating ...
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1answer
67 views

Unit conversion: dBμV to dBm, including measured frequency

I'd like to ask for help with conversion of measured voltage V=10dBμV to dBm units. Voltage is measured on frequency ...
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1answer
1k views

Automotive battery input EMI filtering

I'm reviewing the schematics for an evaluation board, which uses an LC filter on the DC input as shown here: PWR_IN is defined for the evaluation board as being 7-27V. The issue I'm facing, is where ...
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1answer
47 views

Non-isolated DC power distribution for an appliance

I am building an appliance where we have a device where we need to have a +48 V/300 W DC power rail and a +24 V/300 W DC power rail. The AC (mains) should be world-compatible (both low- and high- ...
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2answers
65 views

Help Shielding RF Anechoic Chamber - FM Stations

a collegue and I acquired a surplus small anechoic chamber (8 ft x 8 ft) for making some pre compliance test measurements, and we're running into the issue of FM Stations being only attenuated around ...
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2answers
118 views

Legal to use non FCC-approved radio devices purchased locally?

Does anyone know if it's legal to use non FCC-approved radio devices which are purchased locally? For instance, if the device is purchased from a local eBay seller, is it still legal to use it in any ...
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1answer
82 views

Using neighboring traces for PCB return current

I am developing a 2-layer board for a 3-channel BLDC motor driver. I am using an IC for the driver (DRV8313). I will PWM it at 20kHz with around 10% or less duty cycle. Current is less than 1A. It ...
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1answer
284 views

PC monitor flickers/resets when washer motor switches on or off [closed]

My room is next to our laundry and I've recently got a new PC monitor. I've noticed each time the motor in the washing machine is switched on or off, my monitor flickers/resets. The monitor is 32" but ...
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0answers
72 views

Switching a power contactor from an arduino / raspberry

I'd like to switch a power contactor (such as this one : https://www.legrand.fr/pro/catalogue/31925-bipolaires-250-v/contacteur-de-puissance-cx3-bobine-230v-sans-commande-manuelle-2p-250v-25a-contact-...
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3answers
726 views

Class D power supply filtering for conducted emissions

I have recently designed an audio player that uses the TI TPA3112D1 power amplifier, and mostly based it on the reference design and schematic. I find however, that the design is failing the ...
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1answer
72 views

Feed through capacitor

I have 2 feed through capacitor NFM21PC475B1A3 & NFM21PC105B1C3. These haven't the same capacitance. I want to separate them but I can't measure. Help me what should I do?
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1answer
281 views

Impedance mismatch in LISN for EMI/EMC test

I am currently designing LISN for CE-102 test.The schematic of the circuit is provided below. When I connect the circuit to the network analyzer the impedance is coming as shown below expected graph ...
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1answer
86 views

Routing the signal across the slot opening in the power plane

What happens when we rout a signal trace across the slot opening in the underlying power plane ? Can you please explain the signal integrity issues generated by this mistake ? And what will happen if ...
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1answer
274 views

Suppressing “travelling” EMI spikes

I am working on a circuit with a AC to DC power supply module and wireless MCU module. The MCU operates at 240MHz and on the power input to the module there are 2 x 0.1uF capacitors and a 22uF ...
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1answer
201 views

EN 50121-3-2:2016 radiated immunity frequency range gap

I was just reading EN 50121-3-2 (Railway Applications – Electromagnetic compatibility – Part 3-2: Rolling stock – Apparatus) and noticed in Table 5 that there is a gap in the test frequency between 2....
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1answer
101 views

Connector's placement - EMC [closed]

Why placing connectors on the same edge of the PCB is recommended as an EMC design guideline? As mentioned in https://learnemc.com/pcb-layout All connectors should be located on one edge or on one ...
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3answers
782 views

PCB design - signal loops

I've read about loops that a PCB designer should avoid them "mostly about ground loops" but i think I've read also about power. so in this case, is this wrong: ???
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1answer
80 views

Car 12V Supplied device - Requirements

I am currently designing a device that is intended to be used outside the car and supplied by car 12V socket (also during the drive). The question is: Are there any specific requirements for example ...
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1answer
90 views

How to perform conducted emissions testing for electric generator?

I am doing pre-compliance EMC testing on an electric generator. The standard I am reading explains how to test devices that get power from mains, but it doesn't explain the testing procedure for a ...
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1answer
46 views

Netfilter (230VAC) without protective earth (PE)

I need to filter my mains input, but I don't have any protective earth (PE). Will a mainsfilter (schaffner for example) still be usefull? I think so. I think the mains filter despite of not being ...
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1answer
598 views

61000-4-6 CDN calibration - how to factor in the 6 dB attenuator?

I am seeking some clarification around CDN calibration for 61000-4-6 (RF conducted immunity test). By following the standard and some application notes, I am pretty sure I have it sorted. I just ...
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1answer
85 views

How to route a nasty signal (200V/µs)?

I have to route this signal for a distance of ~70mm† through a dense (mostly digital) 2-sided board. The signal is generated externally and I have no control over its shape, it's basically a pulse ...
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1answer
222 views

conducted emission for smps

My circuit and its conducted emission test result are in the attachment. The circuit is smps circuit for three phase energy meter. As you see it fails conducted emission test. What would you suggest ...
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2answers
287 views

ESD/EMI Design for CE, Recommendation seems wrong from test lab

I have designed a product for a customer, that now needs to pass UL/FCC/CE Testing, It passed UL & FCC but failed CE for both 8kv ESD and EMI. The Chinese test lab my client went through sent me ...
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2answers
824 views

Why does an SMPS use LCR on INPUT?

I have this 5 V output SMPS I bought a while ago. I was wondering why there are LCRs connected to the input of my SMPS. I don't understand why it's there. BTW, I'm an electrical engineering student, ...
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2answers
134 views

Noise on the whole board after USB connection

I designed a device on which there is a HUB, FT232 , two external USB port and some periphery. I wanted to check the noise on the power bus. And I saw only white noise. But after I connect the USB ...
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1answer
77 views

can a PC parallel port produce interference?

Please forgive me for crossing wires on top of IC's but I wanted to get things done, yet still have no luck. Let me explain the circuit. I created a circuit in which three parallel port data lines ...
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1answer
976 views

SD card connector chassis grounding

I have been designing a PCB which includes an SD card connector. As I'm not a PCB designer expert, I was looking for a reference design when I came across with the circuit bellow, extracted from Texas ...
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2answers
194 views

EMC test for PCB board without housing

Our company is exporting our product to European market. To sell it to Europe we need CE mark. so we let the test lab test only EMC(EMI+EMS) because our products usually don't equip any RF nor AC ...
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3answers
3k views

Should cable shields be connected to earth ground, or to power supply negative?

I'm working on a PLC cabinet, and I'm wondering whether I should hook cable shields to earth ground, or to the power supply negative. I checked and the power supply DC output is isolated. There's no ...
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2answers
515 views

How to detect far field noise outside of a certified EMI lab?

For some background, we recently took a product to the EMI lab for EMI Pre-compliance testing and came close to passing, but we have some issues in the 30 to 100MHz range that just put us out of ...
3
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1answer
568 views

Transformer vs capacitive vs both coupling to speaker

I have seen various configurations in my lifetime on how an 8-ohm output speaker is connected to amplifier circuits. Currently I'm doing a project using an LM386 amplifier and I capacitor coupled ...
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1answer
36 views

Can a bilateral switch block transmitter interference and can my board still produce great audio?

I made a circuit in which an ISD1760 chip outputs music via an LM386 IC and I like the quality and volume of sound, however, when I run an HM-TRP transmitter on the same circuit board and the ...
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2answers
117 views

What does metal to metal bottoming mean?

Some connectors datasheets specify the following: Metal-to-metal bottoming for maximum EMI shielding under extreme vibration Reference: Dualok Connectors I have also encountered the following for ...
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1answer
67 views

What are the relations between analog transmission frequency and multipair cable types?

My question is a little theoretical about multipair cables. I want to have some basic understanding about the relation between the multipair cable types and application frequency, length and and EMI ...
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1answer
61 views

EMC conducted emissions go up if input cable is close to inductor

I am measuring conducted emission at the input of a SEPIC converter. At first, the emissions are only about 45 dBµV at switching frequency. But when I put my finger on the SEPIC (coupled) inductor,...
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1answer
97 views

ACM2012-900-2P filter can be used on USB 3.0 lines of a Type-C connector?

I have doubts that this CMF is recommended for USB3.0 due to his bandwidth. I am afraid it will filter the USB signal. Can someone explain better the SCCC21 and SDS21 characteristics from here? https:/...
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1answer
799 views

SMPS chassis ground and earth ground

I'm designing a ultra low noise smps and I have some questions about ground/earth chassis. The main goal is very low noise on DC output. Earth (PE) should be connected to one point (only) to the ...
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1answer
46 views

Would any voltage be induced in this scario due magnetic coupling?

Imagine a source with a 100 Ohm source impedance is coupled to an amplifier/receiver which has 1Meg input impedance and the transmission is done by using two parallel wires signal and return |XA| and |...
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2answers
172 views

What's the current leak path of the electrostatic discharge during an EMC test?

When we develop a new product we need to pass the EMC test,I really wonder what's the current path during a electrostatic discharge test. Here is the test situation: Q1: If the EUT(equipment under ...
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2answers
407 views

Does a 3-winding common mode choke work on PE wire

Update It was pointed out the PE wire has to carry large current in fault condition so using a 3-phase CMC is problematic. In IEC62368-1 (2nd edition) chapters 5.6.3 and 5.6.4 it is implied that the ...

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