EMC tutorials - [1/3] Building an LISN

#114 In this video I look at the specifications and parameters behind a line impedance stabilization network, or LISN. I look at what is the purpose of the various components is and then take a closer look at how the values need to be chosen. Finally I build such a device.
More on the topic:
Part 1: • EMC tutorials - [1/3] ...
Part 2: • EMC tutorials - [2/3] ...
Part 3: • EMC tutorials - [3/3] ...
Datasheet:
ro.mouser.com/datasheet/2/445...
LISN schematic:
drive.google.com/file/d/16oYT...
Coil structure:
www.thingiverse.com/thing:480...
Further reading:
www.tekbox.com/product/Pre-Co...
www.ti.com/lit/wp/slyy136/sly...
Special Thanks to all my supporters on Patreon! Especially @afiskon and Ralf B.!
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[@swift84]

Someone get this man an honorary doctorate in EE

[@crowderglen]

Brilliant videos! I printed out the inductor assembly, wound one core and only measured 4.5uH with 2.5 inch of wire (flying leads) on either end.

[@xDR1TeK]

Good work man. I miss this stuff. My lab is a mess, have neglected it for the sake of few bucks doing coding. Well at least you do the videos for the things that I don't need to do myself. Same learning process 😂.

[@MegaMino31]

Your channel is great man, I watch most of your videos. There are two topics I would like you to make videos because there are not that many videos on these subjects. The first topic is AGCs for sure simple ones, and the second topic is JFETS and how to use them because they are not that common in electronics not that many people know how they are used.

[@p_mouse8676]

congrats on te 10k subs! You deserve many more

[@FesZElectronics]

Thank you! Well the numbers are growing, so well see

[@custodiogomesbarcellos4972]

Great video. Thank you!

[@MegaCadr]

I didn’t notice til now that you are over 10k subs. Congrats!

[@FesZElectronics]

Thank you! I just passed the threshold the other day.

[@renatovallerinibarbosa3086]

Very thank you! Fesz; i am development a finaly work on universit, is a led driver and i was need atecipated the emi of my supply in simulation, this video help-me so much to understand detailedment how a lisn work. I am from Brazil, excuse-me grammaticle errors.

[@UsamaAhmedZeki]

Congrats on 10K will be back when you reach a million

[@FesZElectronics]

Thank you!

[@michaellove7912]

You are the best, keep up man

[@030H]

Thank you, very good.

[@kabandajamilu9036]

So nice explanation

[@kristianTV1974]

I built something very similar for my degree thesis, which was based on the incoming EMC/CE regulations at the time (around 1996)

[@jluke6861]

Thank you for your great video.

[@Chris_Grossman]

Very nice. The only detail I would change is to space the banana jacks on 0.75" centers.

[@Gengh13]

Awesome, I was planning on making one to add at the output of my isolation transformer, but maybe I could start by making one like yours for DC.

[@msthv1588]

Xq. CT p😊😊😊😊

[@tantratron]

Would you have similar video tutorial for LSIN connected to 230Vac-50Hz grid system because your actual LISN is for DC automotive ?

[@abdifatahaden4761]

Why would the filtering inductor not change the output impedance of the LISN?

[@pcboreland1]

I very much appreciate this clear explanation of the workings of a LISN. Could you please provide further info on the wire gauge and number of turns for the 5uH inductor?

[@FesZElectronics]

I honestly don't remember the number of turns, but the wire I used was 0.7mm thick. Anyway, the wire thickness will only impact the maximum current capability - you should chose a wire thickness appropriate for your needs; and regarding turns, I usually just use an online calculator to determine how many I need - there are multiple ways to build this thing. I guess the only thing to keep in mind is that the coil should be spread out a bit to increase the SRF (self resonance frequency) since you want it to be purely inductive in the frequency range of use.

[@andrewphillip8432]

I do a lot of work with instrumentation amps and have found that they are exceedingly sensitive to EMI. Think I might build one of these LISNs to improve my test setups. Thanks for sharing Fes!

[@FesZElectronics]

What sort of issues do you run into? and of course what sort of environment is the circuit supposed to work in?

[@andrewphillip8432]

@@FesZElectronics Running at gain of around 500 (for load cells amplifiers), I get small DC offsets that change by 50mV easily (on the output) when I move my hands near the circuit, or even if I walk around the area near the circuit. Presumably high frequencies are coupling into the inputs and getting rectified. The inputs are biased to ground so I don't think static electric fields are causing this. I have tried a dozen different input RF filter designs based on AD app notes, with varying degrees of success, but I think they are not working effectively since I am breadboarding these and there is no ground plane to carry away the high frequency noise effectively. I have observed that things like connecting multimeter test leads to the circuit seem to affect noisiness to some degree too and my power supply as well, hence my interest in LISNs. Will be using the circuit in a university lab, which other than the florescent lights and electric motors I don't think is particularly harsh EMI wise.

[@FesZElectronics]

Regardless of where you are, one of the major noise sources will also be radio - AM and FM. Especially if the noise is always there, the noise source should be something always running - I'm guessing motors would have a more sporadic behavior. Regarding lightning, in my experience the noisy ones are not the fluorescent ones but rather the LED ones, since those usually contain a high frequency SMPS. Anyway, breadboarding might not be the best option, especially for very sensitive circuitry, but you could try shielding it (a metal cookie box should be large enough to fit the circuit). Another thing you might try is twisting the cables, both the ones running to the sensor and the supply. This should help a lot with differential noise. To be honest, I'm not sure if the LISN is the best option for a supply line filter, I mean using a filter on the supply line might help, its just that you might not need an LISN but a similar schematic with different values (larger inductors should filter better). What sort of measures did you try that had a positive impact? maybe we can figure out the problem.

[@andrewphillip8432]

@@FesZElectronics Yeah I think radio is a likely source. There’s definitely a powerful AM station near me that I’ve had interfere in other circuits. In your experience does wifi couple into circuits easily? I have built an aluminum enclosure that fits a breadboard and I did some testing on the circuit the other day. Unfortunately it didn’t completely solve the issue, although it seemed to reduce it somewhat. In that particular test, I had the instrument amplifier inputs grounded through a similar impedance to the load cells I use, so that way the load cell cable couldn’t be bringing in any interference. The only thing coming out of the the box was my multimeter leads and power supply leads. I tried googling for shielded multimeter leads but I couldn’t really find much information on this. Have you ever seen multimeter leads that are coaxial, or some similar arrangement to protect the positive lead from picking up interference? My thinking is that the interference was getting routed into the box through the multimeter leads and going straight into the output of the instrument amp and getting rectified somewhere inside into the DC offset that I’m seeing. I put an inductor between the test lead and the output of the instrument amplifier and this seemed to have a positive impact. Maybe I should buffer the in-amp output with a fast unity gain op amp so the RF is less likely to get to to the in-amp? In any case I did actually make a PCB for this a while ago but never got around to testing. I will solder it up tonight and see if the ground plane and smd bypass caps cure this headache Edit: I remember one other thing that seemed to help significantly was cutting the leads on my filter and bypass capacitors as short as they could be to get rid of parasitic inductance, so this further points to it being a decoupling issue. It was really cool to see that it made a measurable difference just shortening the leads maybe three quarters of an inch.

[@andrewphillip8432]

@@FesZElectronics Just got the proper pcb soldered up and it works much much better.

[@shubhamnayak9369]

Man how do you build so many projects so fast?

[@typedef_]

He never sleeps lol

[@FesZElectronics]

Lot of coffee also helps :D

[@madjman3688]

@@FesZElectronics, I just looked at the firsts minutes and it looks promissing. For your information LISN name is progressively changing to AN (Artificial Network) in the latest standards. It is easyer to say than LISN ;)

[@MrEsendere]

Indeed if you accept we can bring you inturn students :)

[@shaggygoooxide]

Since most of the field emanates from the ends of the solenoids, I'm not sure the shielding is doing much. I would suggest also covering the tops and bottoms with copper. Also, what frequency are you trying to shield? If it's line frequency, you will need to increase the thickness to about 1cm (skin depth of 60Hz is 8.5mm).

[@FesZElectronics]

I do agree, at 60Hz, the shield would be of little use. But the main frequency range an LISN is used in will be 100KHz to 110MHz so the thickness should not be that big of an issue.

[@SaihoS1]

Have you measured the mutual inductance of the 5 μH chokes? How was the shielding affected the performance of these chokes? Could you please show the frequency response measured with a VNA (like nanoVNA)?

[@FesZElectronics]

Various measurements are planned for the next video concerning this topic. One of the measurements of course is just how well the 2 channels are isolated from one another. I honestly haven't performed the measurement yet but in case I run into issues, the shielding may need improvements.

[@urlkrueger]

I wondered about how EMC testing was done. Now I know more. Had you considered mounting the two inductors at right angles to each other to reduce mutual coupling or would that have made the footprint too big for you?

[@FesZElectronics]

I guess the main reason for keeping the lines (and inductors) parallel, other than the size of the device is to keep a constant distance from the ground plane. Working at frequencies up to 110MHz the stray capacitances and inductances start to have a significant effect, so the 2 channels need to be kept as symmetrical as possible.

[@pfabri]

For the life of me I cannot see how can R2 act as a bleeder -- it's not in series with C1 and C2 (in the simplest form of the LISN). Could someone please point out the glaringly obvious thing I'm missing here?

[@lironuziel6347]

Hi, how does the first resistor on the left, prevent the resonance. And which interruption are there in high frequency from the generator?

[@FesZElectronics]

The capacitor together with the inductor form an LC filter; if there is no resistor, the Q factor would be infinite - at the exact resonance frequency the filter would amplify noise; by adding in the resistor, the Q factor is reduced to a point where the filter actually filters at every frequency.

[@HeroClaws]

Just one more question. Here where im from i can't find any BNC 50 ohm termination resistor, could i use little 50ohm SMD resistor with a little switch to include it in the circuit when I want to do measurements. And one more thing. I've found 0.75mm wire but its braided not like yours (full copper wire). Can I use this braided wire to make 5uH inductor or i need to use "one wire with 0.75mm thickness". Thank you

[@FesZElectronics]

It all depends on the current for which you want to use the LISN. I used 0.75, because I had it around, but becuase its so thick, it can probably handle >5A easily. If you need low currents, you can use thin wire. Braided will not have a negative impact. Having a resistor with a switch is actually practiced in real LISN's to reduce complexity. As long as the wires are short, it should work perfectly fine.

[@HeroClaws]

@@FesZElectronics Got it, Thank you very much

[@WR3slo]

Wouldn't it be better for each capacitor to have a separate resistor in series. They are always scaring me with placing capacitors in parallel will make them resonate at high frequencies. Although those frequencies would probably be too high for DIY LISN.

[@FesZElectronics]

Well its important to mention that the smaller value capacitors also have higher ESR (compared to a similar case size larger value capacitor); but nevertheless the worst thing that could happen is a sudden increase in equivalent impedance at a certain frequency, and we will see if this happens next time when I perform measurements on the LISN. As a side note I did see this technique being implement in commercial LISN also (see the TBOH1)

[@MrEsendere]

I think your nick name should be perfect FesZ inspite of only FesZ. U are really great. Can you mention how you design LISN circuit? Is the man who wounded the winding of transformer also you? :)

[@tHaH4x0r]

You probably misspoke, but at 8:25 I think you probably meant electromagnetic shield, not magnetic shield (as a conductor is not sufficient for magnetic shielding, you would need high permeability material like mu metal). Great video though, not many people go into much detail about their projects.

[@Graham_Wideman]

I think he's using the copper tape as a "flux band" magnetic shield, as discussed here: kzbin.info/www/bejne/jKmTYZyBoLx2adk

[@juliussokolowski4293]

Great stuff... I'm in a battle with my PoE system at home. As a ham, those things drive me crazy with their RFI on HF. But I'll admit it's a damn convinient solution for powering my access points. I'm thinking of a LISN for PoE. In that case I need to measure the supply side and the DUT side. Any ideas for a LISN that could measure both sides? I went at it with a common mode probe and the conducted emissions are there for sure - but a LISN would make testing way more accurate. I tested some ferrite cores on the cat6 line and it did help but I'm not sure what it does to the data rate. Should do nothing - but I'll borrow a network tester and then we'll know for sure.

[@FesZElectronics]

I guess you can use an LISN both ways(just flip it in the circuit and measure the noise on the side on which the measurement port is); in principle the LISN is a bidirectional filter and noise isolator, so once its on the supply line it will allow the measurement of the noise from any side (either from the load or from the supply) as long as the measurement port is on that side of course. Regarding the cable, as far as I could find, "cat6" just means that a certain speed is ensured, but there are both shielded and unshielded Cat6 cables - which type do you have?

[@juliussokolowski4293]

@@FesZElectronics I'll have to wrap my head around how to implement the LISN on PoE... As for the CAT6, mine are shielded... the thing is that the shield is usually connected to GND of the powered device while the PoE power lines are typically decoupled with capacitors to that same GND. Question is hence if any AC that might be present on the PoE power line might be getting over to the shield and having it act as an antenna?

[@FesZElectronics]

Unless you have dedicated supply lines separated from the data lines, I'm not sure an LISN would help. I think the common mode probe is the right choice to perform any measurements that do not impact the integrity of the standard cable - most HF noise is common mode anyway. Also considering that adding ferrites over the entire cable helped, again points towards a CM problem - I guess you could apply a ferrite on the CAT cable at both ends, just to prevent noise form either source - this would make for an easy to implement fix, as long as it does not impact network speed as you pointed out.

[@juliussokolowski4293]

​@@FesZElectronics Both common mode feed and spare-pair are used - depends on implementation. In my case it's actually PoE+ and it puts out power on the data lines as a common mode feed. But I was thinking of doing some research in to the passive mode as well which runs on the spare pairs. In that case the lisn should work. Any ways... a common mode probe and maybe some near-field probes will do just fine to test out what improvements can be achieved. What is frustrating is that I can't find much in the way of publications on this particular subject... Maybe there are some papers in the IEEE library. Where does one look for papers on EMC any ways? Thanks and keep it up! Your videos are a treat!

[@FesZElectronics]

You can sometimes find good documents from various manufacturers of components - for example on a quick google search I found "slua454" and "slua469" from Texas Instruments - honestly I have not looked into the details, but I guess searching for "PoE emc" or "radiated emissions" should help - if the pdf is made by a component manufacturer (the ethernet Ic of the various filter elements) usually it contains valuable information.

[@nicholasroos3627]

404th view. Could not find video.

[@HeroClaws]

Nice build indeed. Can you please tell me the thickness of the copper wire :)

[@FesZElectronics]

I used 0.75mm wire for the inductors.

[@dimitarzhekov9550]

what software is used for the modeling around 7.53 mark?

[@FesZElectronics]

Autodesk's - Fusion 360

[@dimitarzhekov9550]

@@FesZElectronics than you so much !

[@rjrodrig]

Does the coil get warm? Is that PLA?

[@FesZElectronics]

The wire that I used was 0.7mm thick, so it should not get warm unless very high currents are used (>2A); the material is PLA, no special proprieties where needed.

[@felixcat4346]

I can see how this would be useful in a noisy environment like a car. But how do auto manufactures do this?

[@FesZElectronics]

I'm not sure I understand the question. An LISN is a device used to simulate the supply line to make noise measurements possible; its used only under laboratory conditions, not in the real world.

[@bp6331]

AC or DC ?

[@FesZElectronics]

This sort of 5uH LISN is most commonly used to test devices for 12 or 24V DC systems

[@MJ-vt1kp]

i think LISN is only for Conducted emission not for radiated emission ;-) 0:18

[@FesZElectronics]

Well, to measure the emissions, the LISN is used only for conducted; but even for radiated emissions, part of the noise will come from the supply cable, so the LISN is there to fix the lenght of cable that is attached to the tested unit. So the point of using it during radiated emissions is to standardize the supply cable lenght, even if the LISN is not used for the measurement its self (the antenna is) its still part of the setup.

[@MJ-vt1kp]

​@@FesZElectronics I know what you meant but that is tesetup e.g. for Automotive. For commercial, scientific, industrial and medical devices the testetup will be without LISN/AN for radiated emission and you should test your device with cables that you are selling it with.

[@FesZElectronics]

You are right, the setup involves placing the DUT on a nonconductive table, and just exposing the supplied cable for non automotive setups. It does seem strange though to not have any filtration on the supply line. Or is it just a different type of filter (not an LISN)?

[@MJ-vt1kp]

@@FesZElectronics In the semi-anechoic chamber the electrical sockets are EMI filtered (big filter boxes on the wall of a chamber) but I do not know what is seen impedance from input cables side of DUT. Maybe is just low inductance by output capacitors at the filters. Keep up interesting projects :-)

[@mr1enrollment]

all that and the testing is for another time? lost me dude.