Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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. EMC depends upon many system-level details; when asking questions, please provide as much information as possible.

1035 questions
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How to debug emc problem?

First time during my entire engineering career I have been to an emc lab last week. My design has failed to satisfy FCC requirements. The board uses a 25mhz clock and we have failed at 500mhz but I can also see other harmonics being high. It turns…
Ktc
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EMI filter for 1-wire

I have made thermometer with 1-wire sensor (DS18B20). The sensor connected to microcontroller via long (approx. 4m) three wires (GND, VDD, DQ). The wires has no shield. It works, but I worry about EMI. Should I protect wires? If yes, how? Can I use…
user54579
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Crystal Harmonics EMC Failed

I have a failed on EMC Test 300MHz and 500MHz due to crystal harmonics. There is a lot of spike with a 25MHz harmonics. The first picture is the Top of the Board and the 2nd is the 2nd layer underneath the Crystal and the third one is the Bottom…
jasp
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Difference between radiated and conducted emissions?

The company I work for needs FCC certification for an electronic product we are designing. I have watched a couple of YouTube videos on the subject but I’m not clear about the difference between the conducted and radiated emissions tests. If someone…
ben
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Cable shield as ground conductor

I have two circuits connected by a shielded cabled. The cable brings 3.3V DC and LVDS communication between the circuits. The shield is being used as the sole conductor for the reference ground to the load side of the circuit. This doesn't seem…
user37520
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Radiated Field Immunity Failure

I have a system composed of a video processing board connected to a 3-meter flexible endoscope. The endoscope cable has 10 signals (including ground) going to a sensor at the tip and an EEPROM (all low voltage 3.3V, low current 10mA). The sensor…
kal28
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noisy environment between buffer and in-amp

I have some basic questions regarding the circuit shown below: The image is from this question. The buffer is sending signals through a twisted pair cable to an in-amp. My questions are: Does the buffer have other functions than to increase the…
R.Hood
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Relationship between Conducted and Radiated Emission

Maybe it's a silly question but I couldn't find any useful info about this. Sorry for that. I've been asked to design a 72-to-24VDC/6A converter for railway vehicles. I designed one and it works perfect. But our customer wants that the converter…
Rohat Kılıç
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EMI protection for unused pins

I am designing a board that has 2 DB9 plugs/connectors. They are used to supply power(Vcc and GND) and data signals respectively. Now, I wont be using all the pins in the DB9. Some will be left floating. I will then be trying to get FCC/CE…
Board-Man
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How to perform conducted emission simulations

I am currently attempting to design an EMI filter for an AC/DC power supply that is too noisy to pass conducted EMI testing for MIL-STD-461 (115Vrms, 50Hz). In the lab I have measured the DM and CM emissions of the PSU, according to this article: "A…
Lunde
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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( 10^(r0/20) + 10^(r1/20) ) But now, I'm starting…
niCk cAMel
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Microcontroller transmitting to RGB LED via 1.5 m wire

I have an RGB LED present in an EV charging station. The RGB LED uses a digital serial protocol to receive colour information from the MCU. The cable length between the two is 1.5 m and it's all enclosed within the charging station. The RGB LED…
Hari
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Is it allowed to place a capacitor between the LISN and the DUT using CISPR25 spec?

I am very new to the EMC world (co worker quit Friday and now its my problem) I was asked by my supervisor to check the CISPR25 spec to see if it is allowed to put a 1000 uf cap between HV+ and HV- between the LISN and the DUT. I have the CISPR25…
kjones734
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How do AC/DC Adapters (Wall Wart) prevent AC Noise Coupling to DC?

I am wondering if AC noise (EMI) gets coupled to the DC side of the AC/DC adapter, what are the design methods used to isolate AC noise getting coupled to DC output in an AC/DC adapter. What are the relevant AC/DC adapter (Wall Wart) specifications…
Niloy Talukder
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Reading analogue sensors in a noisy environment

I need to read the values from several analogue sensors mounted on a circuit breaker in an electrical substation. I'm not working with any high voltages, but the circuit must still work as the breaker switches normal operating current (not fault…
William
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