5uH LISN for Spectrum Analyzer EMC/EMI work

[georges80]

Hi Folks, I recently purchased a Rigol DSA815-TG primarily for EMI debugging/snooping. I've purchased and made a few near field probes and current clamps and been busy crimping coax connectors to RG174/LMR100 and generally getting the RF side of things put together.

So, next on the list was a LISN to check conducted noise issues from DC power inputs. Saw the Tekbox unit and since it is nominally open hardware with schematics/bom and layout available I figured it would be cheaper* (and more instructive) to build one up versus purchasing it ready made.

First step was to verify component availability from the tekbox bom (mostly digikey stuff) and then do my PCB layout since I prefer to have my own database versus someone elses gerbers. Created a few footprints and then layed the board out being reasonably faithful to the original layout. I used a gerber viewer to measure some of the key dimensions (especially the inductor spacing) to replicated it into my pcb cad file.

To get a netlist I entered (from scratch) the schematic into Orcad and here's a screen capture,

essentially the equivalent of the tekbox schematic (can be found at www.tekbox.net):



Once I had the netlist I could import it into the pcb cad program and verify all the footprints and connectivity. A couple of hours later and here's a screen capture of the PCB layout I put together:



The layout was sent off to PCB fab about a week ago, so I should receive boards back this coming week. Simple 2 layer board, soldermask/silkscreen etc. Ordered 20 boards since their individual cost is somewhat minimal compared to setup/shipping. More about that later. I ordered components from Digikey & Mouser and most of them are pretty cheap so 20 sets of parts are in my hands. The only parts I didn't order up in volume were the box, bnc connector, GDT etc. I order from Digikey often (too often), so getting more of those parts later is a non-issue.

With one box in my hands I decided to move ahead (since boards are in fab and dimensions are cast in stone) and start drilling some of the holes - for the PCB and BNC to start with.

So, here's the box with a few holes, small drill press makes life easy and a step drill does a neat job on the larger BNC hole. Next to the box is a 1:1 print of the layout, makes it easier to visualize and verify mounting location and hole placement.



To verify the air wound inductors were the values claimed in the original schematic I wound a test inductor with some scrap wire onto the former and then checked it with my DE-5000 and sure enough inductance was in the 1uH range. I'm still waiting on the nominal new 1.4mm diameter (16awg) enameled wire to arrive - should turn up Monday. So, I turned a 17mm former on my minilathe in preparation for winding the actual inductors.

Here's a picture of the former machined from some scrap delrin with the inductor wound on it:



This was wound from scrap wire (16 awg as it turns out) that I recycled from a power inductor. I had to straighten the wire so it still looks a bit rough. The results should be nicer when I get the new wire that comes on a spool.

Based on the physical dimensions of the inductor, I entered the parameters into an online calculator:

http://wcalc.sourceforge.net/cgi-bin/air_coil.cgi

The coil former is 17mm diameter, so the effective coil diameter (at 1/2 the thickness of the wire) is (17mm + 0.7mm x 2) = 18.4mm. The coil measured length is approximately 12.4mm. Wire diameter is 1.4mm and 7.5 turns. Calculated frequency independent inductance is about 1.02uH



and here is the DE-5000 reading of the inductor. Certainly close enough. I did calibrate the DE-5000 with the croc clip adapter plugged in.



Pic of some of the parts waiting for the PCB's to turn up:



That's where I'm up to at this point. Hopefully later in the week I'll have the PCB's in hand and can assemble up my unit. I'll post up more pics as the build proceeds.

*So, what about the other 19 boards?? I figure if some folk on this forum want to buy a kit I can purchase the remaining components and ship them out as kits. I'll include the PCB, all the components, banana jacks and the BNC that need to be soldered to the board and the wire that you'll need to wind on a former. I won't include the box. Cost to cover the PCB/components (likely $30 per 'kit') + mail/packing (which will depend on US/international).

Most of the discrete components are SMD, so you need to be comfortable soldering those parts - though on this board they are quite large (0805 is the smallest part)... Anyhow, first let me get the PCB's in and build one unit up.

cheers,
george.

[Circuitous]

Neat!  I look forward to updates on your project.  I expect to need a LISN in a few months for another project.

[georges80]

The new 16g enameled wire turned up this morning.



I made a mod to my former, drilled a hole in the side to hold one end of the wire and also made a bit of a trench (hot soldering tip) for the wire taper. Makes winding the coils so much easier.

Winding a coil on the former:



4 coils done, just need the PCB's to turn up:



cheers,
george.

[Rufus]

Saw the Tekbox unit and since it is nominally open hardware with schematics/bom and layout available I figured it would be cheaper* (and more instructive) to build one up versus purchasing it ready made.

As I pointed out in the blog thread the Tekbox design and the way Dave used it is garbage. I was hoping someone more expert would comment but I guess we haven't got any here or they couldn't be bothered.

[georges80]

Feel free to explain where the issues with the unit are. It is meant to be used with a ground plate and screwed/bolted to it as per their manual. The ground posts on the unit are the grounding points. Dave's video of course side steps the full setup procedure presumably to simplify his task in the demo.

I hope you can educate us with why it won't work as shown in the tekbox manual for DC power supply conducted emissions. I'm NOT planning to use the unit for accuracy, it's use in my case it to identify the conducted emissions (frequency/harmonics etc) and then use that information to resolve issues that are in the design and/or front end filter circuitry.

cheers,
george.

[Rufus]

I hope you can educate us with why it won't work as shown in the tekbox manual for DC power supply conducted emissions. I'm NOT planning to use the unit for accuracy, it's use in my case it to identify the conducted emissions (frequency/harmonics etc) and then use that information to resolve issues that are in the design and/or front end filter circuitry.

I already did but I will say it again

As said in the mail bag thread it is arsed up anyway. You can't properly measure anything on a power supply pair with a single channel LISN. If you stuck a capacitor across the UUT side of that LISN you would short out most of what you are measuring while such a capacitor would have no effect at all on common mode signals.

That LISN is crap being manufactured and documented to support the way Dave used it.

You absolutely don't connect equipment ground wires to the ground plane. A single channel LISN is only useful for testing equipment which has a single wire.

[georges80]

You seem a little 'excited'... Anyhow, I'd be glad to read some explanations of how it is all meant to be designed and used - got any good links for me to read up on?

cheers,
george.

[T3sl4co1l]

Simple remedy: make two!  Which fortunately you have the boards for

Remember of course, it's for automotive work or whatever, whereas an AC line grade unit needs 150uH.

I made one of those.  It's untested as yet, but evaluating the inductors seems to suggest it won't be grossly (like >10dB) out of whack.



Tim

[georges80]

Rufus: Well, I've done some reading and searching on the web and I've found several descriptions of a 5uH scheme with the same basic topology as the tekbox LISN. They are indeed used to measure conducted EMI in vehicle type applications, which is exactly what I need to use it for (DC power source/battery feeding the DUT which in my case is a LED driver).

So, for my use, the tekbox design certainly appears to be applicable and not 'garbage'.

cheers,
george.

[Lunasix]

I also made one, because it was too expensive to order it for France. I made inductors with a lathe, very easy and perfect result, a copper spring ! I've checked my boards and improved power supply with a better filter design. But I'm not an expert...

[georges80]

Blank boards arrived today from the PCB house:



Unfortunately some shelving arrived today too and reorganising the mess I call my work bench takes priority. So, it'll be tomorrow before I start to assemble my LISN. More pics to come then.

cheers,
george.

[EEVblog]

Rufus: Well, I've done some reading and searching on the web and I've found several descriptions of a 5uH scheme with the same basic topology as the tekbox LISN. They are indeed used to measure conducted EMI in vehicle type applications, which is exactly what I need to use it for (DC power source/battery feeding the DUT which in my case is a LED driver).
So, for my use, the tekbox design certainly appears to be applicable and not 'garbage'.

That is correct as I understand it too. I may have failed to mention in the video that there are many testing scenarios, and the Tekbox is suitable for just a subset of them.

[Jay_Diddy_B]

Hi,
I am going to share my implementation of a 5uH LISN. I used carefully selected SMD inductors instead of the traditional method of winding air-cored inductors. The inductors are Wurth 744314110.

I also incorporated a combination 10dB attenuator, limiter and 9kHz High Pass filter into the design. The attenuator / filter is to protect the spectrum analyzer from damage.

The style of construction was chosen to make the LISN performance very predictable.


Schematic
This is the schematic diagram:



Attenuator / Limiter / Filter Design

LTspice model:



Modeling Results:



Board Design



Construction
The board is designed to replace the lid of a Hammond 1590 diecast box.



Testing
This graph from a HP 3753C Network Analyzer shows the attenuation from Load Connection to the Spectrum Analyzer connection. It is flat within 0.5dB over the range 2MHz to 100MHz.



This Smith chart shows the input impedance from the load connection. After 2.6MHz the input impedance is pretty close to 50 Ohms. This matches the requirements for a CISPR 25 LISN.



The performance of this LISN has been compared to a commercial LISN and found to agree very closely.


Jay_Diddy_B

[T3sl4co1l]

About the only thing better you could do -- I would guess -- is staggered inductor values, or maybe some C or R+C on some of the inductor nodes (taps).  Exactly how much (of either case!) would depend.

Either way it's quite flat, as it should be!

Tim

[Lunasix]

Here is my lisn made according Tekbox schematic. Probably not perfect, but helped me to improve switching power supply on my boards.

[georges80]

Finished the initial tidy up of my work bench:



and soldered some of the parts down on the new board:



and the back



I have the banana jacks turning up hopefully Sat, Mon worst case and then will drill their holes  wire things up. Also a couple of components that I forgot to order before will turn up.

Here's a trial fit into the box



and the BNC (have a locknut coming just to make it more structurally sound)



I'll have to remove the enamel coating on the ends of the 4 coils I wound and solder them in place too.

More updates in a few days. I've also ordered enough parts to kit up 10 units for folk that have PM/Email me with an interest to buying a kit or two.

cheers,
george.

[georges80]

Remaining few parts turned up and I finished assembling the board. Drilled the holes for the banana jacks and installed the finished board into the box:



First test was to play with a LED driver (the DUT) to measure the conducted noise back to the power supply. Just a rough test to get a feel with how things work:



So, with the DUT connected directly to the LISN I scanned and stored the yellow trace. Lots of conducted noise up to around 300MHz. Then I wired inline (you can see the red/black croc clips and blue/yellow wires) a simple LC pi filter built rough as guts christmas tree style. The purple scan shows the noise level with the pi filter in place. The noise floor is at -68dbm with the DSA settings.



Very pleased with the instant gratification. More time to learn/educate myself with the capabilities, but for a quick inspection and assessment of problems and possible solutions it seems to be a great little addition.

I have parts on hand (all except the box). $30 per kit + postage (based on US or international) will cover costs. I'll provide the schematics & gerbers (including Orcad & PADS datafiles, I'll put them up online).

cheers,
george.

[Jay_Diddy_B]

Hi,

It looks good.

It would be interesting to see a sweep from 150kHz to 5MHz with an RBW setting of 10kHz. You should be able to see the switching frequency and its harmonics.


I would recommend using a 10dB attenuator on the Spectrum analyzer to protect the input. It is much easier to replace than get the analyzer fixed. We an HP SA you set a pre-amplifier gain. When I use an external attenuator I set the SA pre-amplifier gain to -10dB so the display on the screen is corrected for the external attenuator.

You can also use the tracking generator in your Spectrum Analyzer to check the LISNs performance. Feed the Tracking generator to the load side of the LISN and the BNC connector to the SA input.

Regards,

Jay_Diddy_B

[georges80]

Hi Jay,
 yes, I have a 10db attenuator in my "bag of tricks" - but thanks for reminding me to USE it

The performance should match the texbox data (since it's a "clone"), but I do plan to play with a lot more and sweep it etc.

Lots more testing to do as I get time (precious commodity!).

I've decided the easiest way to kit these - after sticking components down on a schematic printout is to just solder the R's & C's down and provide semi-built kits. Fast to just put some solder paste down and reflow than tape them down on a sheet of paper and less chance of folk loosing parts or mixing up the C's... Folk will need to solder down the mov, gdt and wind their own air coil inductors etc.

cheers,
george.

[georges80]

Had a bit of time to do a scan of the LISN. First step was to get the signal through the coax and to the LISN DUT connectors. Obviously signal integrity is key to getting a good scan, so I ended up stripping just the end of the coax and enough ground braid to touch the case (bare metal) and the center conductor to touch the banana jack pin.

I did normalise the TG with the same coax making contact with the BNC center pin of the input cable. Obviously the ideal case would be to have a coax BNC soldered right onto the PCB. As is, the TG signal is traveling through the banana jack and the wire that solders down to the PCB. Not the greatest impedance match for doing a scan.

Nevertheless the scan looks pretty damn good out to 180MHz. If I can be bothered I'll see about soldering a coax connector onto the PCB to get a better scan of the LISN characteristics, though it seems to perform great all the way to the 100MHz 'spec' and pretty good even way beyond 180MHz if you can live with 2db 'ripple' (some of which may just be an artifact of the coax/banana jack connection.



cheers,
george.

[georges80]

So, I soldered the coax directly to the PCB (no BNC), just direct soldering to the LISN DUT input and the internal BNC ground.



Doing that of course improved the signal integrity of the measurement and the LISN measured performance is much better than the previous scan.

Here's the full 1.5GHz scan to see how it behaves:



Then a scan to 500MHz.



A scan up to 200MHz:



and finally the low freq (up to 5MHz) performance:



So, from about 2.5MHz to 200Mhz it is flat to within about +/- 0.25db. I consider that pretty good performance and will now move on to actually using the unit for its intended application.

cheers,
george.

[T3sl4co1l]

Willing to bet the junk over 300MHz or so is due to parasitic resonances of the coils (helical waveguide modes) and board.  Maintaining a 50 ohm characteristic impedance from DUT connectors to the BNC would help (of course to be fair, the DUT side needs to be a clean 50 ohm termination as well).  Graded choke sizes, rather than equal dimensions stacked, would probably help.  (Really wideband bias tees use ferrite cored, conical inductors!)

Just for S&G, not really useful... I wonder, do you have any ferrite rods, or shapes that would fit inside the coil?  A piece added to the supply end might absorb some of the lower frequency energy bouncing around.  However, placed in the DUT end, it would probably attenuate too much.

Tim

[georges80]

The tekbox design is meant to be for up to 100MHz, so the performance is 'good enough' given it seems very flat all the way to 200MHz. My application is to ensure that my DC : DC LED drivers are 'quiet' through the FM band and this will deal with that. Even to 475MHz is only deviates about 1db - I'm happy enough.

It's primary use (for me) is to evaluate input power filtering to my drivers and this unit appears to easily be able to meet that requirement.

If you want to experiment - feel free to buy a kit  , but thanks for the suggestions. When I have some free time I may play with it some more, but at this point I need to USE it.

cheers,
george.

[EMC]

Hello,

I have been involved in automotive EMC for some time. I also have a DSA815 and was thinking of making some 5uH V Networks, or LISNs.   These look good.   A couple of comments:

> air core inductors are definitely best
> housing should be diecast but will impact on the air core inductors
> phase is also specified in CISPR 16
> impedance & phase must be verified, including housing influence, with a VNWA (see DG8SAQ https://www.sdr-kits.net/)
> impedance & phase verification done at the DUT side with PS side shorted
> the network becomes more & more useful the higher it goes at 50 ohms; you start to get confidence in radiated performance
> only one input and one output required; everything else is connected to the diecast housing
> they must be used in pairs, one for positive one for negative; best bonded to a small ground plane
> only one at a time connected to the DSA815; the other must be terminated with 50 ohms on the RX output
> 1uF required across the power supply input (option to switch out for transient immunity testing)
> the MOV needs to be switched out for transient immunity testing
(the noise under test develops voltage over the specified inductive reactance; the 1uF gives low impedance and is critical/fundamental to a good result)
> best operated from a battery (R_int typically 0.01 ohm) to ensure low impedance at the input with a PS (R_inttypically 0.10 ohms) in parallel for charging between tests

When used in pairs the test setup emulates intended environment; i.e. power cable to the DUT.   If the positive result is higher than the negative result then differential suppression, cap to ground.   If positive and negative results are the same then common mode suppression.   If negative result higher than positive result then DUT ground scheme is wrong.   This is all just very general and typical.   Result will have two types of 'character'; broadband and narrowband.   Broadband to be measured with quasi peak (9kHz BW <30MHz & 120kHz BW > 30MHz); 'brush on rotor' type noise.   Narrowband to be measured with average detector; uP XTAL and harmonics.

Typical Limits in dBuV:
LW 0.15 to 0.30 MHz QP 77 AV 70
MW 0.53 to 1.8 MHz QP 57 AV 50
SW 5.9 to 6.2 MHZ QP 52 AV 45
FM 76 to 108 MHZ QP 37 AV 30

Steve

[didjado]

i have had some Pcbs made and have a quite a few left over if any one wants the smt stuff is all placed by machine and all you have to do is put the  inductors and the in put out put wires on...

i needed one and put it on a panel that was being made now i  have heaps of them... i will put some images up  so that the response can be viewed

if any one is keen

[georges80]

I've used the LISN for several designs over the past 3 or so months and am happy to report that it truly works well and provides an excellent correlation to the real world.

I've taken a few designs that would wipe out the FM band and with some changes to the design (input power filtering to the led drivers) and some power plane layout changes those drivers are now totally quiet.

On one driver (2 layer board in that case) I could cut pieces of copper from the ground plane under the filter area and the improvements seen on the DSA reflected as improvements in lower FM interference.

So, in summary, the tekbox LISN design DOES work really well and for the cost of the DIY version it's an excellent addition to owning a DSA for quantifying conducted emissions (for *DC* powered circuits) and then observing improvements (or not...) as you implement changes.

cheers,
george.

[HighVoltage]

Hello George
This is very good information you are leaving here, thank you.
Can you share the details of your different designs and how you use the LISN correctly.
May be some pictures of the setup?
Thanks

[georges80]

I've attached a few pictures showing the LISN and DSA in use testing a buck/boost LED driver. The driver is mounted to the back of an MCPCB with 6 XML running 3A a piece, so about 60W to the LEDs.

The picture below shows the noise levels with power turned off. The small peaks are FM stations being received via the DUT power cable. The rectangular aluminium plate is to prevent the LEDs from burning spots in my antistatic mat



The next picture shows the driver powered up and the conducted noise on the power leads to the driver. This noise level is a lot lower than with the original driver that did not have a common mode choke at the input (the black rectangle to middle/right on the PCB).



The next picture has the same setup, but a 0.1uF capacitor is making contact between the IN- of the LED driver board and the aluminium of the MCPCB. Noise levels are much reduced and you can see some of the FM radio station peaks showing through. Noise is now essentially below the FM received strength using the power leads as an antenna

At this level practical tests show the driver (in a housing with the LEDs and longer power leads) will not interfere with FM radio reception even if the power lead is wound around the vehicle antenna - good enough!

'

So, this is an example of reducing emissions and being able to observe changes in real time by making changes to filtering and ground paths etc. It's not testing for compliance, but testing for a design that is proven to not interfere in the real world on an actual vehicle.


I am currently working to bring another design through FCC qualification at a local EMC lab. Our first run through had issues and based on what we did in the lab to identify the actual sources we discovered that one of the HDMI cables we used had huge leakage at the connector end (likely not shielded in the connector end where the cables are then soldered) and also that the AC/DC adapter we were using had nasty broadband noise in the 30MHz - 70MHz range.

I then brought my DSA to work along with my LISN and also a beehive probe. The LISN showed the same broadband noise shape with the AC/DC adapter plugged into the DUT end of the LISN. I could then apply a load at the Power supply end of the LISN to see how the noise of the adapter increased. Then we tried various other adapters and found one that was actually FCC approved having essentially no noise emissions.  This proved that the LISN does a great job of identifying conducted noise that will then radiate (as measured by the antenna/emi receiver setup at the EMC lab). I then used the beehive (nearfield probe) and probed various HDMI cables and confirmed all were quiet at the cable and connectors, EXCEPT for the 'bad' HDMI cable.

It has been a learning experience, but with several real world check points between the LISN/DSA and the Beehive, I am becoming confident in what my setup shows and how the unit will behave with nearby radios etc. The test lab results add a lot of credibility and correlation between my setup and their measurements. Certainly these tools allow for pre-compliance testing to at least identify things that will surely cause you to fail.

cheers,
george.

[wemme]

Hello,
I am looking at making a LISN for preliminary scanning MIL461/DO160E.
These are based around 50uH inductors and not the 5uH as used for automotive.

Does any one have any construction notes about building these?

Regards
Bart

[wemme]

Hey Jay_Diddy_B

Thanks for sharing your design,
Any reason you used such a large discrete solution for the attenuator and filter?
filter aside Wouldn't a simple pi or T attenuator be adequate for a 10dB with 50ohm in/out impedance.
Regards
Bart

Hi,
I am going to share my implementation of a 5uH LISN. I used carefully selected SMD inductors instead of the traditional method of winding air-cored inductors. The inductors are Wurth 744314110.

I also incorporated a combination 10dB attenuator, limiter and 9kHz High Pass filter into the design. The attenuator / filter is to protect the spectrum analyzer from damage.

The style of construction was chosen to make the LISN performance very predictable.


Schematic
This is the schematic diagram:



Attenuator / Limiter / Filter Design

LTspice model:



Modeling Results:



Board Design



Construction
The board is designed to replace the lid of a Hammond 1590 diecast box.



Testing
This graph from a HP 3753C Network Analyzer shows the attenuation from Load Connection to the Spectrum Analyzer connection. It is flat within 0.5dB over the range 2MHz to 100MHz.



This Smith chart shows the input impedance from the load connection. After 2.6MHz the input impedance is pretty close to 50 Ohms. This matches the requirements for a CISPR 25 LISN.



The performance of this LISN has been compared to a commercial LISN and found to agree very closely.


Jay_Diddy_B

[Jay_Diddy_B]

Hey Jay_Diddy_B

Thanks for sharing your design,
Any reason you used such a large discrete solution for the attenuator and filter?
filter aside Wouldn't a simple pi or T attenuator be adequate for a 10dB with 50ohm in/out impedance.
Regards
Bart

Bart,

I did not invent the 10dB filter / High Pass filter. It is a copy of the HP 11947A. Details of the HP 11947A can be found here:

http://www.keysight.com/en/pd-1000001160%3Aepsg%3Apro-pn-11947A/transient-limiter-with-high-pass-filter?cc=US&lc=eng

The 10 dB is distributed over 2, 3 and 5 dB attenuators to spread the power out in an overload situation.

You can use a standard 10 dB attenuator on the front of the spectrum analyzer, and many people do.

I like the idea that the mixer and attenuator in my spectrum analyzer are protected. It is much easier to rebuild the protection circuit than repair the spectrum analyzer front end.

I have also built just the attenuator and limiter in box, without the LISN.

I first used this circuit in a line voltage LISN. The construction is similar to the low voltage LISN. I had two copies of the entire circuit, one for line and the other for neutral. The key components were:

PHE850ER7100MR03R06L2 for the capacitors on the line side, these are 1uF 300VAC Y2 class

PHE850ED6100MD18R06L2 for the 0.1uF capacitors from the load side to the attenuator. Chosen for safety.

Wurth 7443331000 10uH 9A Inductors, times 5 to get 50 uH. Chosen for high self-resonant frequency and shielding.

Construction was similar to two copies of my low voltage LISN, inductors in the center, attenuators on the outside, about 110mm x 110mm.

I hope that this helps.

Regards,

Jay_Diddy_B

[wemme]

Wurth 7443331000 10uH 9A Inductors, times 5 to get 50 uH. Chosen for high self-resonant frequency and shielding.
Jay_Diddy_B

Hi Thanks for all the information that explains a lot.

Did you have any issue with the cored inductors rather than air?
was your line lisn 110 or 230V?
Regards
Bart

[Jay_Diddy_B]

Hi Bart and the group,

Did you have any issue with the cored inductors rather than air?
was your line lisn 110 or 230V?
Regards
Bart

The inductance of the inductors is not super critical. Ideally the LISN should look like 50 Ohms to the input. The impedance of the 50 uH is 314j Ohms at 1 MHz.

Here are some pictures of my LISN








I did a measurement of the input impedance using an HP 3577A Network analyzer with a s-parameter test set. One of the challenges connecting the power connector to a coax cable. (Where is my precision N to power connector adapter?)



The return loss is 23 dB at 30 MHz



This is a picture of insertion loss. Ideally it would -10db and flat. It is hard to normalize this measurement because the power connectors are not very good at 50 MHz 



Since this is used for pre-compliance testing, you compare the results against the results from the lab.

Regards,

Jay_Diddy_B

[mk_]

Maybe this pdfs are helpful....


michael

[wemme]

Thanks for sharing all the information this is very helpful.
Has anyone built or using a common mode/differential splitter with their lisns?
Regards
Bart

[Jay_Diddy_B]

Bart and the group,
 
It is relatively easy to build a resistive splitter/combiner to distinguish between common mode and differential mode noise. Here are some schematics using WYE (3 x 16.7 Ohm resistors) or Delta (3 x 50 Ohm resistor). Keep you cable lengths between the LISN and the splitter the same to maintain the phase relationship.



If the noise is differential it will be reduced, ideally it will cancel. If it is differential it will increase.

Fairly easy to construct, a box, three connectors and three resistors. I don't find them too useful, because I generally know when to expect differential or common mode EMC.

Jay_Diddy_B

[ivonenand]

Schematic


Jay_Diddy_B

Hi,
I'm just drawing up my own version of this LISN and I have a question regarding the component selection. Are there special L1 (1mH inductor in the filter) requirements? The best ones I've found have the SRF of about 2.5MHz, which is allot lower than the 100MHz line where the LISN is still designed to work. Or am I missing something?

Much appreciate any info,
Ivo

[T3sl4co1l]

As long as the impedance of that inductor is well above 50 ohms at frequencies up to 100MHz, it's okay.

Wirewound inductors tend to have many peaks and valleys above their first SRF, but it's probably not too bad.  To a certain extent, you can put other RFCs in series to cancel those out, but you have to be careful not to make a worse circuit instead (i.e., the parasitic capacitance of the large inductor goes series resonant (low Z) with the next inductor).

Tim

[Jay_Diddy_B]

Hi,
I'm just drawing up my own version of this LISN and I have a question regarding the component selection. Are there special L1 (1mH inductor in the filter) requirements? The best ones I've found have the SRF of about 2.5MHz, which is allot lower than the 100MHz line where the LISN is still designed to work. Or am I missing something?

Much appreciate any info,
Ivo


Hi,

Before I built the LISN, I built just the attenuator / High Pass filter portion of the circuit. I too was concerned about the 1mH inductor. Here are some pictures:











The frequency response was measured with an HP3577A Network Analyzer. The measured results show no significant deviations from the results predicted by modelling.

I have tried several inductors, it does not seem to be critical.

Regards,

Jay_Diddy_B

[NikWing]

Jay_Diddy_B, the maximum DC input voltage is limited by the 2 caps close to Vin, right?
The tekbox LISN can handle 200V IIRC. I might need at least 50V (more wouldn't be that bad though, just in case), so all I have to do is to use caps that can handle this voltage?
C2 seems to be an elcap and C1/C3/C4 are MLC?

Next question is, 4148 are fast enough? I've seem other LISN using ESD protection diodes or TVS diodes.
Since you're already using it, I guess it's no problem, right?
And, all 4 should be mounted?

[Jay_Diddy_B]

Jay_Diddy_B, the maximum DC input voltage is limited by the 2 caps close to Vin, right?
The tekbox LISN can handle 200V IIRC. I might need at least 50V (more wouldn't be that bad though, just in case), so all I have to do is to use caps that can handle this voltage?
C2 seems to be an elcap and C1/C3/C4 are MLC?

Next question is, 4148 are fast enough? I've seem other LISN using ESD protection diodes or TVS diodes.
Since you're already using it, I guess it's no problem, right?
And, all 4 should be mounted?

Hi,

just to make sure we are talking about the same thing, here is the schematic that I am going to talk about:



and this construction:




This type of LISN is normally used for low voltages 48V and less. It is not a line voltage LISN.

I used MLCC for all the capacitors. The blue component is the inductor L1. I used a 250V capacitor for C3 and 100V capacitors for C4 and C5. C1 and C2 can be low voltage components.

The diodes are small signal diodes, you need low capacitance.

The limiter is styled after the HP11947A. The documents can be found here:

http://www.keysight.com/en/pd-1000001160%3Aepsg%3Apro-pn-11947A/transient-limiter-with-high-pass-filter?pm=PL&nid=-32400.536881615&cc=CA&lc=eng

HP used 1901-0050 diodes, which are 1n4750, they have 2.5pF of capacitance.

I did not invent the circuit, I changed (slightly) the attenuators to use E24 series resistors.

It works great.

Regards,

Jay_Diddy_B

[NikWing]

yeah, we're talking about this one, well nearly XD
I found this thread while doing some SA researches, then I googled "5µH LISN" and found this github page:
https://github.com/LibreSolar/5uH-DC-LISN
and it links back to this thread, so I somehow thought it's an improved version of the stuff you posted earlier (because the files are 7 months old and the 1st similar looking circuit was from 2014)

so finally I'm mixing up people, sorry ... a bit overworked at the moment XD

Okay, so the point is low capacitance for the diodes.

But beside that, if I would use higher rated capacitors on the input and decoupling path (and maybe also replace the elcap with MLCC), there wouldn't be any drawbacks if I understand it correctly?
since the DC part of the supply voltage is decoupled and we're just looking at the alternating voltage part.
Or do I overlook something?

[Bud]

HP used 1901-0050 diodes, which are 1n4750, they have 2.5pF of capacitance.

Are you sure, 1n4750 seems to be a 27v zenner

[Jay_Diddy_B]

HP used 1901-0050 diodes, which are 1n4750, they have 2.5pF of capacitance.

Are you sure, 1n4750 seems to be a 27v zenner

Sorry, small mistake.

HP 1901-0050 = 1n4150

link to datasheet: http://www.vishay.com/docs/85522/1n4150.pdf

Regards,

Jay_Diddy_B

[PDonchev]

Hi,
Great thread! I already made two 5uH LISNs according Jay_Diddy_B design and they helped me a lot in my first EMC troubleshooting steps.
I have one question to Jay_Diddy_B:
What are these elements on the picture (in the red circles)?

[Jay_Diddy_B]

Hi,

In each red circle there are two 475K resistors and a piece of track. They are to discharge the 1uF capacitors.




Regards,

Jay_Diddy_B

[dcarr]

Jay_Diddy_B,

Is there a place where I can download a copy of your LISN gerber files?  Your design looks great and I'd like to build one for myself.

It seems silly to take the time to re-CAD the whole thing if I can use your proven design files.

Thanks,
David

[PDonchev]

Hi dcarr,
NikWing posted a link to github with project of 5uH LISN almost identical to Jay_Diddy_B's LISN.
Actually, I used that project to build my LISNs.

[PDonchev]

Hi,
Thank you for your reply.
I have one more question, did you mount the 330 ohm resistors?

Hi,

In each red circle there are two 475K resistors and a piece of track. They are to discharge the 1uF capacitors.




Regards,

Jay_Diddy_B

[NikWing]

just a quick update:
I got the PCBs now and most of the parts
after I've built the 2 LISN boxes, I'll report back

[NikWing]

alright, I assembled it and just made a real quick test and now I'm not sure if everything is alright
(SA setup for this quick test: preamp on, attn: 10dB, 150kHz-30MHz, 100k/1k for BW)

1st thing I notice: the RG58 BNC cable is about 30 cm. I see peaks on the SA without anything connected to the LISN when preamp on the SA is on. They disappear if I press the LISN case against the input connector GND (and probably remove the GND loop of the cable I guess)
2nd: I get random "ADC overload" warnings, for example when I connect the PSU to the LISN, if I short circuit the PSU after the LISN etc (there's no voltage on the BNC if I use a multimeter to measure)

what exactly should I set on the SA? I did not have much time to play around today, but I did not yet find out how to compensate the LISN's attenuation in the SA
I guess I should still enable the SA's attenuation and set it to 10dB
I see/measure peaks if I enable the SA's preamp but nearly nothing if it's off. But these peaks clearly come from the DUT (and change if I make changes on the DUT)

The LISN does not have the 4148 mounted yet.
Now I'm not sure where to start improving the whole setup to have something I can use to make significant and repeatable measurements.

(oh, just in case: these are my 1st steps using SAs )

[Jay_Diddy_B]

Hi,

You may see some local AM radio stations if you connect the LISN to a spectrum analyzer. You can identify if they are local stations from the frequencies.
Here is a picture from my lab.



i

So long as the interference from the local stations are around 6dB below the limits you don't have to worry about them.

Check your setting against the ones shown on the screen:

Vertical unit dBuV
Vertical reference: 100 dBuV (top of the screen)
Pre-amp gain: -10 dB (to compensate for 10dB attenuation in the LISN)

RBW 9 kHz ( use 9 or 10 kHz)

Frequency: 150 kHz to 5 MHz.



Can you post a picture of your spectrum analyzer screen?

Regards,

Jay_Diddy_B

[NikWing]

alright, let's see ...
I suppose preamp gain is Ref Offset on the Siglent

pic 1: preamp is off, ref lvl 100 dBµV

pic 2: preamp is on, ref lvl 87 dBµV is the maximum I can set

[Jay_Diddy_B]

Hi,

It looks like it is working correctly. The noise level with the pre-amp off is around 25dBuV, the same as the noise floor on my measurement.

Trying hooking up a switching power supply.

Regards,

Jay_Diddy_B

[NikWing]

I was a bit unsure about the noise, it looks less noisy in your screenshot but I did not see any reference at the 1st glance

ok, pic 1: no LISN connected
pic 2: LISN connected, DUT is a 5" Nextion Enhanced ... PreAmp is off

again, I'm a bit nervous: the moment I connect the PSU, the SA warns about ADC overload, not everytime, but 30-50%

[rauol]

Very Nice work, are the gerbers available.
Regards

[ferdinandkeil]

I've just finished my own copy of the LISN. So far it seems to work properly, however using my own equipment I could only check it for flatness from 500 kHz to 25 MHz. Will post some pictures once I've measured it with a proper network analyzer.

The PCB was designed in KiCad. Being my first layout in KiCad it might not look super pretty. It is designed to fit a Hammond 1590B diecast aluminium box. The holes I've placed did not fit the box, but luckily I could fix it using a PCB mill. Please find the KiCad and GERBER files attached to this post. The second version of the PCB should have the drills in the correct location.

Thank you Jay for making this design available 

[slug13]

I am a little behind the rest of the folks here in this blog.
I am just beginning to build the 5uH LISN per the Tekbox plans.
I have almost all the components now but am dismayed by the tiny size of the TVS diodes specified. They are only 0.8 x 0.6 mm and I don't think I will be able to hand solder them.
I wonder why the designers chose such tiny devices for ESD protection, and which are rated only at 150 mW ??
Then they add the 60 volt gas tube in parallel which seems a little on the over-kill side.
Has anyone used alternatives, like a pair of 1N4148 diodes back to back, or as I was thinking 1N5711 schottky diodes back to back?

[Ranganok]

Hello everyone,

I'm trying to build an LISN of 5uH but I run into several doubts:

- How can I measure impedance? I have a VNA (SVA1015x) and I think it has to be connected to the power ports (like attachment picture) of the LISN but I'm not sure.

- The metal box is necessary, but how much is necessary? I want to use an extruded aluminum box type (https://www.banggood.com/en/15010555mm-Aluminum-Instrument-Box-PCB-Enclosure-DIY-Electronic-Case-p-1080020.html) is it possible? Or should the enclosure of the box be without grooves?

Regards,

[ferdinandkeil]

Attached the measurements.

DUT_PORT_MEAS_PORT shows S12 from DUT port to measurement port.
DUT_PORT_SMITH shows S11 at the DUT port.
MEAS_PORT_SMITH shows S22 at the measurement port.
POW_PORT-DUT_PORT shows S21 from power input port to DUT port.

The LISN is very nice and flat up to more than 100 MHz. Should be usable at higher frequencies as well.
Impedance at the DUT port is well behaved. Same is true for the measurement port.
Isolation between power input and DUT port is high.

Measurement was done using an Agilent E5062A.

[r0d3z1]

anyone have a couple of this homemade LISN for sale ?

[jonpaul]

Hello all

The industry standard is Solar Electronics

This link has all the types and many useful app notes.

https://www.solar-emc.com/LISN.html

In our lab, we used the 50 uH 10 A version 7225-1

You can find them on eBay and at Ham Radio Fleas.

Do not count on the transient protection Zeners  to save your Spectrum Analyzer front end!

In any 2 sided LISN NEVER switch the line/neutral with analyzer attached!

Just the ramblings of an old retired EE

Enjoy

Jon

[r0d3z1]

Georges80 could you please indicate the model number and manufacturer of the metal case that you used ? Thanks

[georges80]

BOX ALUM 4.51X2.52X2.17" Hammond   1550D   Digikey   HM1184-ND


cheers,
george.

[r0d3z1]

I have finally been able to build the LISN and test it.
There are 4 test condition

• LISN connect & PREamp off
• LISN connect & PREamp on
• SA background noise & PREamp off
• SA background noise & PREamp on

the SA is a new rigol rsa3015e, the test setup is with 2 LISN and metallic reference plane. For sure I still don't have

• a good low impedance wiring between battery negative terminal and metallic plane
• a good low impedance wiring between negative lisn terminal and metallic plane. Some suggestion on how to make it good with the banana connectors ?
• the right 50ohm termination on not used lisn (I have incorrectly bought the 75ohm )
• 1uF and 1000uF capacitor on the supply side of lisn as dictated by CISPR25

What do you think about ? is it an overall good result ? I am very uncertain about the peak at 15MHz visible in the image LISN-noise-PA-0-30

Here is some screenshot, the filename comment itself.



this tool is very useful to compare the pictures.
https://www.diffchecker.com/image-diff

[prasimix]

Just sent into production a LISN PCB built using the schematics that @Jay_Diddy_B sent me . I arranged it so that it goes directly into the Bud industries EX-4521 enclosure. The front and rear panel are also PCBs, something I have long wanted to make .

[ferdinandkeil]

Just sent into production a LISN PCB built using the schematics that @Jay_Diddy_B sent me . I arranged it so that it goes directly into the Bud industries EX-4521 enclosure. The front and rear panel are also PCBs, something I have long wanted to make .

Awesome, very slick layout. Please post pictures once it's finished 

Are you planning to sell / open source the design?

[doktor pyta]

It seems that we have follower of idea by Jay_Diddy_B.
https://www.ebay.co.uk/sch/herczegz992/m.html?

[Noy]

 Die somebody build the Lisn from here:
https://github.com/LibreSolar/5uH-DC-LISN

Little differences in schematic / layout. Is it good and can be copied?

[T3sl4co1l]

Looks fine.  Give or take exact component values, or if you want limiters or attenuation or what, which is all up for grabs on final assembly.  I'd cut out the ground under the inductors, and add a few spots for optional damping resistors.  And obviously you need two for most purposes, or higher inductance and some voltage clearance for mains (probably including bigger capacitors for the voltage rating).  Not a big deal.

Tim

[Noy]

THX, i'm new to these things. Still waiting for arrival of my SA/VNA.
I'm only working on DC <60V so do i need 2 devices for DC ?

Why is this design using 2 serial caps with instead of 1 in the other?

You mean cut out on "top" on the opposite side from the inductors? I thought it is for shielding because there is no additional case top like the tekbox approach.

Why 10db? I mean 3.61 is uncommon? Better 6db (2) or 20db (10) ? I don't understand why 10db is used in this designs.

Edit: Can answer myself. Forgot power db its 10 not 20 (Volt) for 10x..

[Jay_Diddy_B]

Hi Noy,

I know as much about this circuit as anybody 

THX, i'm new to these things. Still waiting for arrival of my SA/VNA.
I'm only working on DC <60V so do i need 2 devices for DC ?

Why is this design using 2 serial caps with instead of 1 in the other?

You mean cut out on "top" on the opposite side from the inductors? I thought it is for shielding because there is no additional case top like the tekbox approach.

Why 10db? I mean 3.61 is uncommon? Better 6db (2) or 20db (10) ? I don't understand why 10db is used in this designs.

Edit: Can answer myself. Forgot power db its 10 not 20 (Volt) for 10x..

The design shown in this post:

https://www.eevblog.com/forum/projects/5uh-lisn-for-spectrum-analyzer-emcemi-work/msg404662/#msg404662

is my original design.

I gave the design to Linear Technology and they developed the DC2130A demo board that can be found here:



The Linear Technology design was copied and presented here:

https://github.com/LibreSolar/5uH-DC-LISN

When Linear Technology made their version, they made three changes:

1) They increased the thickness of the traces on the inductor wiring:




This makes the RF performance worse.
This is addressed in their demo board manual. They suggest lifting the inductors off the board to minimize the capacitance to the ground plane.

Look at page 15 of this document:

https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/DC2130AF.PDF

(I have since built a few versions of the my original LISN using a single-sided PCB, no ground plane, and they work even better.)

2) They added a 22uF 100V Electrolytic across the input. The useful part of the electrolytic is the ESR. It is providing damping. This can be analyzed like this:




These models look at the impedance of the LISN for different conditions on the input.
There is OPEN, SHORT and inductance. The inductance represents the wiring between the LISN and the power source.




The results show that if the wiring and the LISN is in the approximate range 0.1uH to 0.5uH the LISN doesn't meet the impedance specification.
If the 22uF capacitor, including 1 Ohm ESR, is added it does.

This is a good change.

3) Two capacitor in series.

This is done to as an extra safety measure to protect the spectrum analyzer input in the event that the capacitor fails short.
The change in effective capacitance from 0.1uF to 0.05uF has very little impact on the RF performance.

Since there already is the 9kHz HP filter, built into the LISN, there is little benefit to this change. It does not make the performance worse.


I consider this a neutral change, neither good or bad.

10dB

10dB is a very easy number to work with on a Spectrum analyzer, since they typically display amplitude on a log scale. On my spectrum analyzer, there is a setting for an external pre-amp. I set the pre-amp gain to -10dB. This corrects the display for the attenuation in the LISN.

Regards,
Jay_Diddy_B

[Noy]

 Many thx for the detailed discription.
Only question left:
Do i need 2 if im using DC only?

And some former designs from me radiated emission oder GND.
Is the shown lisn also then useable or do i need 2 then 1 for. + one for und?
Or can i simply change the in/out polarity? Or something else?
Or is it enough to put inductors into GND path?
But then which GND is used for SA connection / attentuator? Dut or supply?




Edit: GND Planes are probably added to prevent bending during reflow process.

[Noy]

Did some tweaks on the github design.
Would you suggest to cut out the GND plane on top right above the inductors?
Thought GND Plane is for shielding.

Tweaked the resistor valus to the LT ones and added a resistor in series to the 22uF cap (don't like to use a electrolytic caused by polarity and dampening can be adjusted). Changed to SMA connector (use it more than BNC).

Will order it from JLCPCB in Black.

Im still not sure if i need 2 ones for DC supply.. And like i asked if i have a noise / radiationed GND. How to measure? Additional Inductors into GND? Or how?

[TimNJ]

You basically always need two LISNs, unless the DC input wires are very short (<200mm per CISPR25), or if you have a "single wire" DC system, that is, the return current is allowed to conduct through the metal chassis of a vehicle or aircraft (DO-160, for example).

The need for two LISNs is not inherently related to the fact that AC switches polarity. In an ideal world, a device's input current is purely differential-mode. But, in the real world, there will almost always been common-mode currents on both input wires. Common-mode current must return externally, through earth, or at least the surroundings. These currents tend to cause EM radiation. The justification for why short wires, or "single wire" systems are exempt is, I believe, that those configurations are less prone to radiation in this way.

For a "normal" two wire input, the LISN should provide a symmetrical impedance for common-mode currents on both wires. I suppose there could be issues with common-mode-to-differential-mode conversion (or vice versa?) if the impedances do not match.

More generally, the impedance presented to EMI currents will be different if you leave one side out. The equivalent circuit of a dual LISN presents 25 ohms to common-mode currents, and 100 ohms to differential-mode currents. By changing the "load" seen by these signals, you may change the amplitude detected at the port on the LISN. The limits in CISPR11, etc. are defined with the expectation that the CM and DM currents see these impedances.

Something I don't understand, and maybe someone can help to clarify, is why single LISNs are allowed (for the above mentioned exemptions), even though the DM impedance will be 50 ohms instead of 100. Won't this affect the results?

[Noy]

When i'm generally need 2 of these boxes for DC.
Why is Tekbox selling them as single?

If i need 2 it is only that i need the inductors also in GND path or?
So i can also tweak the PCB to have additional inductors in GND  or? Which GND for Attentuator / SMA then? DUT or Supply side?

[Jay_Diddy_B]

When i'm generally need 2 of these boxes for DC.
Why is Tekbox selling them as single?

If i need 2 it is only that i need the inductors also in GND path or?
So i can also tweak the PCB to have additional inductors in GND  or? Which GND for Attentuator / SMA then? DUT or Supply side?

Hi,

If you know that the conducted emissions are differential mode noise, then you can use one LISN for pre-compliance testing.
Most of time with small power supplies the conducted emissions are dominated by DM mode noise so this is justified.
If you use one LISN the DM mode signal twice a big, 6dB, higher than if you use two LISNs. This is because half the DM signal will appear on one LISN and the other half on the other LISN.

The difference between 50 and 100 for one versus two LISNs normally isn't important because the emission source impedance is usually very low.

You can build a double LISN like this:




(This is a LISN designed for CISPR 32)

(A shoutout for the ZofzPCB Gerber viewer - www.zofzpcb.com)

If you use two LISNs you can use a DM/CM Separator to determine if the emissions are CM or DM.

I described the construction of one of these in this thread:

Link: https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/msg3117396/#msg3117396

Regards,
Jay_Diddy_B

[TimNJ]

When i'm generally need 2 of these boxes for DC.
Why is Tekbox selling them as single?

If i need 2 it is only that i need the inductors also in GND path or?
So i can also tweak the PCB to have additional inductors in GND  or? Which GND for Attentuator / SMA then? DUT or Supply side?

If you use one LISN the DM mode signal twice a big, 6dB, higher than if you use two LISNs. This is because half the DM signal will appear on one LISN and the other half on the other LISN.

The difference between 50 and 100 for one versus two LISNs normally isn't important because the emission source impedance is usually very low.

True, true. If we model the source impedance as...1 ohm, then the difference in EMI levels will be around 1%, with a single LISN (50 ohm DM impedance) vs. dual LISN (100 ohm DM impedance). The 1 ohm number is just a guess though. But just to clarify, mostly for Noy, even though the loading effects of single vs dual LISN are not (usually) significant, with a single LISN, the detected level will be twice as high for the reason you mentioned. If going the single LISN route, maybe he/she can put a 6dB attenuator between the LISN and spectrum analyzer/receiver, or tell your EMI software to drop the detected level by 6dB.

All that said, in my limited experience, CM noise is usually not insignificant. But, that's limited to a certain variety of power supplies. If you don't have a good feeling about whether your DUT will produce significant CM noise, then my recommendation is to use two LISNs. At low power, the BOM difference is not significant. For high current LISNs, the BOM cost may be more significant.

[T3sl4co1l]

Generally there isn't much common mode from a device that only has two terminals (i.e., the power cable and no other connections), but it can still appear, as the device itself has capacitance to free space, thus there is a return path for CM at high frequencies.

If there are additional connections, then not only can there be unbalanced currents among them (and therefore CM back to the LISN), but external connections should be terminated in a similar way, e.g. telecom pairs through a CDN (see for example CISPR 22).

There aren't many applications for a single terminal device, but it might happen in automotive components for example, where one power wire goes out, and return currents flow through the chassis -- in the lab, the ground plane.  This would only need one LISN port, by definition (there's no point in connecting a port to the reference plane, it's defined as zero).

Generally, short or permanent connections between components of the EUT should be laid out in a representative fashion.  Maybe they'll act as stubs and affect the EMI profile of the EUT, who knows; hence, "representative".  Some standards do perform measurements on such cabling, adding loading ferrites to trim the impedance, using current clamps and inductive or capacitive couplers to read emissions or inject noise...

The assumption underlying all of this, is that the system can be analyzed as a network between a number of ports.  The LISN is an interface, joining an endpoint of the EUT's network, to a source, which might be passive (a termination resistor say), or a transmitter or receiver.  The response across multiple ports may or may not be relevant (NM on wire(s); CM/DM on wires in a cable; between cables; etc.).  The point is, everything required is available on ports, so that whatever the desired analysis is, it can be performed (e.g., using a CM/DM splitter transformer).

Tim

[Noy]

I changed some things at the schematic.
But I'm unsure about the correct cap values on the supply side. Which one do i need and which value is needed?
Is it important for EMI precompliance to know if its CM/DM is? I cant remind that in the laboratory there where different CM/DM measurments. Only if the emission is to high or not. Normally i have to measure for EN55011 or EN55022 where can i find my needed L/C values for these kind ?

[TimNJ]

The scanned EMI level is the composite (addition) of CM and DM noise. The standards do not put limits on CM or DM individually, but both contribute to the EMI profile of the DUT. If you only use on LISN, potentially you will have inaccurate/misleading results, if your DUT produces excess CM noise, since you will not detect it. If you do not know the nature of your DUT (whether or not it produces significant CM noise), it's best to test with two LISNs.

[Noy]

I will add additional onto the pcb this thing:
http://www.hottconsultants.com/techtips/CM_vs_DM%20Conducted_Emission.html

Then you see both mixed and if you use the "additional" SMA Connector you only see CM. So you know the difference betwaeen the measurments will be DM.

[Jay_Diddy_B]

Hi Noy and the group,

The circuit presented here:
http://www.hottconsultants.com/techtips/CM_vs_DM%20Conducted_Emission.html

Although this circuit has been widely used, it has a flaw. I analyzed that circuit in this message:

https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/msg3117440/#msg3117440

It does not have the correct impedances.

Regards,
Jay_Diddy_B

[Noy]

Currently I'm unsure if i need the 5uH or 50uH "version".
For EN55011 or EN55022 it looks like 50uH is defined?

So can i simply change the Inductors to one of these? Most times <=5A would be enough for my devices:
74439358100
74439370100   
74439346100

Biggest one 74439346100 is 10uH and can provide 10A. But i don't know if i have to watch for something special about the inductors. SRF for example?

Who knows and give me an advice?

[Jay_Diddy_B]

Hi,

Both EN55011 and EN55022 are mains voltage requirements.

The 5uH LISN described in this thread is only suitable for low voltage applications (automotive).

For mains voltage you need something like the TekBox TBLC08.

Jay_Diddy_B

[Noy]

Ok i will clarify my needs.
I'm using things like these for example:
https://www.phytec.de/produkte/single-board-computer/phyboard-polaris-imx8m/

These Boards are supplied with a purchaseable "standard" 24V DC switching supply (24v dc wall supply for example https://de.rs-online.com/web/p/steckernetzteile/2008925/?cm_mmc=DE-PLA-DS3A-_-google-_-CSS_DE_DE_Stromversorgungen_%26_Transformatoren_Whoop-_-(DE:Whoop!)+Steckernetzteile-_-2008925&matchtype=&pla-307135182373&gclid=Cj0KCQiAqdP9BRDVARIsAGSZ8An3vs9U2hcnP5g-zV_VPg37654AlK4-xgcftCQzSOeWuRK68km0nSYaAutnEALw_wcB&gclsrc=aw.ds ).

I will measure the EMI of this Board when it is supplied from my linear regulated  laboratory supply ( set to 24VDC).

Which LISN do i need? 5uH or 50uH if it is not automotive more like a industrial gateway without a specified AC/DC supply? For example:
 https://www.compulab.com/de/products/iot-gateways/iot-gate-imx8-industrial-arm-iot-gateway/


Found this in an older offer from an EMI Laboratory for a device from me, supplied with an unspecified 24VDC supply (battery / wall supply / lab supply):
EN55011 / EN55032 for emmision
And EN61000-4-6 for robustness.
                                                       

[Noy]

OK it looks like EMI laboratory simply use the EN55011 / EN55022 LISNs (CISPR11 / CISPR22) also for our DC devices.
So i will need a 50uH version with >=5A <=60V.

I think i will use the shown schematic and change some values. For the inductors i will use 7443331000 ones. These are enough for >= 5A and <60V.
And SFR with 35MHz should work or? I must measure 150kHz up to 30 MHz.
I found something that there are 250uH inductors in the AC ones. But these are for AC filtering only or? So i can build it without. I only need 50uH and 5Ohm with sufficient caps?

The CM/DM circuit is flawed you said. But how big will the "failure" be? Is it good enough for indication if CM or DM is the bigger part? I ask because its easier to put this additionaly on the pcb vs. the coupled inductor part especially if this transformer is not the easiest thingy and "pretty big".?

[T3sl4co1l]

SFR can be somewhat below 30MHz even, as long as it is the parallel resonance (maximum Z == least attenuation of signal).  The hazard is the first series resonance, or whatever the impedance is doing up there.

Inductors with certain distributions of losses, can work just fine well past there, as long as you don't mind that the impedance is real, that it's sufficient for it to be high enough (e.g., >500 ohms for a < 1dB error on a 50 ohm system).  This is the general plan behind stacking inductors, particularly in a geometric series, and often with added lumped losses (resistors or RC or RL networks) to control the series resonances between adjacent inductors.

Mind that the inductors need to not saturate at whatever peak current you're using them at; otherwise those peaks will be attenuated at low frequencies.

Tim

[Jay_Diddy_B]

Hi Noy and the group,

I suggest that you read this thread:

Link:https://www.eevblog.com/forum/projects/5uh-aerospace-lisn-how-dumb-would-i-be-to-throw-one-together/

From that thread, this image shows how the inductor SRF has little impact on the LISN:



The impact of inductor saturation was measured by connecting two LISNs back to back:



In this message:

https://www.eevblog.com/forum/projects/5uh-aerospace-lisn-how-dumb-would-i-be-to-throw-one-together/msg3199564/#msg3199564

Regards,
Jay_Diddy_B

[Noy]

Thx for clarification.
So i have started again i found this (see attachment).

But I'm unsure if i need this 250uH thing at the input. My guess was i will simply use the 5uH LISN approach here uwith other values.

5x 7443331000
And other 2x 4uF caps at the supply side in series with some resistors (maybe 4x 1206 parallel for the 5 Ohms) or so.

And the stuff going to the spectrum analyzer nearly the same  except the first resistors -> should be 1k .

But my DC lab Supply has output caps so i think i need something in there that the 5Ohm resistors are used. But 250uH for 5A is pretty big..
So anny suggestions? Maybe anoterh 1-2 x 7443331000 towards the DC Supply are enough?

[Jay_Diddy_B]

Hi Noy,

The Wurth 7443331000 is a good choice for the inductor.

I use 4x 2.2uF capacitors in parallel to make the 8uF

I use 2x 10 resistors in parallel to make the 5 resistor.

This is the schematic:




You need two copies of this schematic.

Build the circuit like this:




The 1k in your schematic is a safety resistor it keep the output of the LISN near ground if the LISN is not connected to a 50 load (Spectrum Analyzer).

My schematic includes a 9kHz HP filter, which is also a dc block, and a 10dB attenuator. These are to protect the spectrum analyzer.

Do not change the 'first' resistor to 1k .

This will result in a low voltage LISN suitable for around 5A and <50V.

The 250uH inductor in your schematic works as a line filter. It keeps noise from the input appearing on the LISN output. If you feed the input with a clean bench power supply, not a switching supply, you do not need this filter.

Regards,
Jay_Diddy_B

[Noy]

So, did some work..
Will also do a LISN Mate in 1590B case and 2 of your  Transient Limiter in 1590A case.

Short question, is it affordable to put additional in parallel to the 1mH inductor something like:

https://www.mouser.de/ProductDetail/MACOM/MADL-011021-14150T/?qs=%2F9lm7XkpNBiyHlfXH%2Fm8aA%3D%3D

Especially if i build the transient limiter which i will also use together with antennas?

[Jay_Diddy_B]

Hi Noy and the group,

I have looked at the PCXB design proposed by Noy. The copper area on the connections to the device under test should be reduced:





They should be reduced to the minimum that is required to handle the current, like this:





This is done to reduce the capacitance to the ground plane. If you don't do this, there will be a resonance at around 30-40 MHz.


Transient Limiter

This LISN has the transient limiter built in. There is no benefit to adding a second transient limiter. It will reduce the signal amplitude by an additional 10dB.
This transient limiter is based on the HP 11947A and will provide adequate protection.
There is no benefit to adding a PIN diode limiter in parallel with the inductor. It will not work, the PIN diode limiter has to be capacitor coupled.

Regards,
Jay_Diddy_B

[Noy]

Thx for your advice.
Corrected it.
For all who are interested, please find attached die Kicad Project.


Edit: Updated Projekt Files (Silkscreen, recalculated trace with for CPWG), added Gerbers, BOM, Schematic PDF

Edit2: JLCPCB charges 4$ engineering fee but i don't know why.. gerbers are looking fine..

Edit3: Found out why.. PCB is taller than 102x102mm...

Edit4: Updated Silkscreen for µH / Version Marking

Edit5: Corrected pcb edge radius to r=5mm

[doktor pyta]

Many thanks to Jay_Diddy_B and Noy who decided to share his PCB project.
Below photos of assembled dual 5uH LISN. This is previous revision of Gerber files with corner radius slightly too small.
I made two units with different inductor types to see the difference.
A minor change in Noy's design is using Jay_Diddy_B's resistors values in attenuation section.
One comment is that soldering to footprints without thermal reliefs is difficult and in my case pushed me to use SnPb solder.

[Noy]

Many thx for these nice pictures.
My pcbs arravied today.
Hopefully i can start soldering in the next days (busy currently).
I will always use snpb for hobby stuff which is better to solder. But with my JBC it shouldn't be to hard even with pb free Söldner, but want to try my recently purchased reflow oven this time :-).
Also the Lisnmate pcbs arravied but still waiting for the emallied copper wire.
If its working i will upload these files also in the lisnmate thread.
 Many THX to Jay_Diddy_B for his work, knowledge and that he was willing to share all the informations i needed.

By the way the attentuator values i used were picked from the LT Lisn reference design evalkit. Which are probably picked from here:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://doc.xdevs.com/doc/HP_Agilent_Keysight/HP%252011947%2520Operations%2520%26%2520Service.pdf&ved=2ahUKEwj_4Ij_x6HuAhWB26QKHefPB0kQFjADegQIBRAB&usg=AOvVaw23v23AWnXR7s4jgAUFknHP

[th_sak]

Just sent into production a LISN PCB built using the schematics that @Jay_Diddy_B sent me . I arranged it so that it goes directly into the Bud industries EX-4521 enclosure. The front and rear panel are also PCBs, something I have long wanted to make .

Hi prasimix,

Can you share more info for your project?
Have you assembled it?
Did it work?
Can you post schematics and/or gerbers?

Thanks

[Knuddel]

Thanks Noy, great project!

Am I right when calculating the thickness of your LISN-PCB to 0,7mm? This is because at least the 1,231mm trace to the SMA-connector should have an impedance of 50 Ohms.
This is calculated with FR-4 to 49,35Ohms for this 1,231mm trace, then.
Please correct me if I'm wrong!

For the CM/DM-Seperator I found a trace of 1,65mm width that is calculated to 51,5Ohms with a PCB-thickness of 1mm?

Thanks again as always also to Jay Diddi!


 

[Noy]

No 1.6mm jlcpcb: With 1.53mm fr4, 0.035mm cu and er of 4.5 for fr4 and gap of 0.2mm .
But not microstrip! Coplanar wave guide with ground.

[Knuddel]

Okay,

thank you Noy!
That is very welcome information as calculator for coplanar waveguide with ground is very rare to find a tool for...
I didn't found it on easyeda or jclpcb but ordered there, too.
In AD19.1.7 this calculator is missing. It was added later in AD20 and tuned up to AD21.
Which PCB-tool did you use for this calculation?

Please, can you calculate the thickness of Jay_Diddy_Bs DIY DM/CM Seperator design?
(https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate/msg3117396/#msg3117396)
The Trace width is 1.65mm and the gap is 0.28mm there.
Seems that it needs a different PCB thickness then...

[Knuddel]

Found this online tool:
https://www.leleivre.com/rf_coplanar_gb.html

It seems that the resulting impedance is relatively insensitive to the gap and trace width with this coplanar approach.
Online tool calculates 1.6mm for the DM/CM PCB, too.

[Jay_Diddy_B]

Hi group,

I used this calculator:

Link: https://chemandy.com/calculators/coplanar-waveguide-with-ground-calculator.htm

2mm trace with 0.5mm gap on standard 1.6mm Fr4 (Er = 4.5)

is close enough for this application.

In practice there is a large impedance discontinuity between the LISN and the device under test.

The trace length in this projects is around 50mm. At 100MHz this represent 1/60th. of a wavelength. You don't have to worry too much about mismatch.

[Noy]

So, now with a proper PC.. It's a mess to post here with a mobile (Android T9  tries everytime to convert english word into german.. an the "dancing" smileys are slowing down my phone..)

Used the same calculator as Jay_Diddy_B:

Coplanar wave guide with ground, used these calculators (crosscheck):

http://wcalc.sourceforge.net/cgi-bin/coplanar.cgi
https://chemandy.com/calculators/coplanar-waveguide-with-ground-calculator.htm

and the given JLCPCB values:

https://jlcpcb.com/capabilities/Capabilities

4.5
1,53mm (0,035mm copper on both sides and 1.6mm pcb -> 1,53mm FR4)

PCB values:
Gap 0.2
Trace 1.231 (if JLCPCB did it right, this shoud be the trackwith)

This gives me 50.04 Ohm / 50.00 Ohm depends on the calculator.

Please find attached last Project files like i ordered the PCBs. Also some sweeps and pictures. The files have correct radius for Hammond 1590B cases (cheap from china, but the holes are a it off compared against genuine datasheet.. but it fits..)

[Noy]

rest of the files..

Used Diodes 1N4148W-7-F (lowest capacitance i found in 1N4148 diodes) and Epcos B88069X1023T203 also relative low capacitance..


One thing i missed in the design files.. i expanded the clearance on the bottom layer like Jay_Diddy_B told but forgot the clearance on top.. 
But i think the sweeps are ok so i will not change something..

Will upload the design files for CM/DM seperator in the other thread..

[Jay_Diddy_B]

Noy,

In reply 103, you have a post a selection of measurements made with a Siglent SA or VNA. What are you measuring?

From the DUT port to the RF ports you should measure -10dB like this:





Jay_Diddy_B

[Noy]

Currently I'm not really common already with these kinds of measurments.. The SSA (now SVA) was my selfmade christmas present 2020..

So my ref is set to 0dB and an SA internal Attentuator of 20dB is activated. So my sweep from DUT banana to HF output is the shown trace with ~ -30dBm.

Incorrect? 20dB internal + 10dB external = -30dB or am i wrong?

One thing i currently don't understand is:
I set the internal Attentuator to 0dB and set the TG output level to 0dB (normaly its -20dB) and it was connected through the lisn.
Then the SA beeped and said that die ADC is in overload was a bit frighthend then.. But why? Input is up to +30dBm and if i set TG to 0dB and internal to 0dB and i have external -10dB why could there be an overload? My ref level was 0db..

Also if the internal Attentuator is -20dB + external -10dB and the used TG has an output of -20dB why not -50dB in total? Its -30dB? Or is the SA compensating the TG out?

Unsure... have to learn a lot and hopefully didn't kill my input mixer first..

Thats the point why i want a Transient Limiter with the already purchased PIN diodes..
Next PCB i will do together with a OPA659 active probe....

[essele]

I've read this thread with great interest as I'm keen to start understanding more about EMI testing for a specific (hobby) project I'm working on. Clearly I don't *need* to do any testing, but I'm planning on open sourcing the project at some point, and generally it's for use with sensitive test equipment so I do want to at least have a rudimentary idea that it's not doing anything too nasty ... also it's a great learning experience.

An overview is here for reference (it has moved on a bit since then, I'll post an update shortly): https://www.eevblog.com/forum/metrology/yaugi-4-gpib-ethernet-poe-adapter/

So this can be PoE powered, using a DC/DC converter of my own making (which inevitably will need some work) and can also be powered from USB. So I'd like to build something that allows me to test these ports.

In CISPR 32 (or the UK equivalent at least) there is the following example schematic for an AAN (which I'm assuming is the same as a LISN??) for anything up to 4 balanced pairs. Which I'm assuming will cover the four pairs in the ethernet port and the data pair in the USB?? (I'm also assuming I'd need something like the above to test the USB power side??)



So I though I might have a go at building something like this, I'm very happy to make loads of mistakes and learn from the experience. But I'm not really familiar with the inductor side of this (L1/L2) .. I'm assuming for L1 for example, that there are 9 1.4mH inductors wound on a common core? Is that as simple as getting a ferrite rod and winding 9 different coils on it, if so, then when measuring each inductor for accuracy would I need to terminate the others some how? Is spacing between them important? Or am I just biting off something that's too difficult?

Any help really appreciated.

Lee.

[T3sl4co1l]

If you read further in that standard, I think you will find construction details, or maybe it's in a related standard I'm not sure.

If you start with 4 pair STP, the 9th (receiver) winding is the shield.  All you need for the inductor is a core with enough winding area to fit the required turns.

For the DM chokes I recommend pot cores: they have high A_L and short turn lengths, minimizing electrical length of the winding, which appears as a stub transmission line to the signal pair.

I made a smaller one here: https://www.seventransistorlabs.com/Precompliance/index.html

Tim

[essele]

Just to report that I've also completed a 5uH LISN using the design from Jay_Diddy_B and Noy -- thanks!

I think I've got a pretty good response curve for both ports ... this was tested using a dual-banana to BNC adapter (which annoyingly I had to hold in place because the distance between the pos/neg and GND isn't standard???)

So I rigged up a pass through using as similar a setup as possible (including BNC to SMA adapters), used that as a reference and normalised. Then attached the LISN in the path (using the DUT port and the output.) I tested positive and negative (to GND) separately. Both look very similar and give a pretty flat 10dB and it only really starts to drop off above 250MHz, hitting about 14db at 500Mhz.

I then checked the impedance after a SOL calibration ... this isn't quite so good ... between about 6Mhz and 40Mhz it's 60ohms ... but I'm not sure what the bounds of "good" actually are. I've plotted a 501 point result so it's easier to see, but I'm not entirely sure I'm doing this correctly. I'm interested in pointers on this and if there's anything I can tweak (if needed.)

My first tests with one of my projects didn't really reveal much other than some intermittent peaks below 150kHz, so I need to find a few more things to look at, and I don't have any of the ground plane stuff in place.

This was built using PCB's from JLCPCB (using the original KiCad designs just with a bit of a silk screen tidy up on the component side) and most of the components from LCSC, I think it was only the inductors, the keystone test jacks, and the enclosure that came from Mouser.

Lee.

EDIT:  Just noticed the "UNCAL" on the SVA screenshots, need to investigate this, not noticed it before. Also just spotted how bad the test jack soldering looks on the photos ... looks much better in real life, but clearly needs a bit of work ... I think I need a bigger soldering iron!

[Jay_Diddy_B]

essele and the group,

You need to terminate the RF port with 50 when measuring the input impedance or you will measure 61 .

Consider this:



Repeat with the RF port terminated and report back to the group.

Best regards,
Jay_Diddy_B

[essele]

Thanks Jay_Diddy_B ... that did the trick although I'm not sure I fully understand the rationale. (Excuse the very poor quality termination, it was the easiest thing to do quickly!)

You will notice I've done it the other way around, terminating the DUT port and measuring through the RF port and I'm assuming that it doesn't really make a difference as it it can be used to inject also??

The impedance is excellent now, with pretty much 50 ohms from about 3MHz through to 160MHz.

So I had assumed that the RF port needed to be 50 ohms to provide a matched input into the VNA, but in normal use the DUT port is unlikely to be 50ohms surely? Therefore it won't be correctly terminated and the RF port will not be properly matched? I am new to all of this, so it's highly likely I just don't understand!

Thanks,

Lee.

 

[Noy]

Hi, nice to see other build. And yes also figured out that i forget to set the bananaplugs in "standard" dimensions... Sorry..

But it's not a huge impact. normaly you wouldn't use BNC cables to power your devices or? ;-)

[oz2cpu]

link to where to order the ready made PCB's ?
or gerber download ? so we can order our self ?

no need to reinvent the wheel :-) 

PS: thanks a million times for your time and energy and shared designs, both files, measurements
implementations, found and tested parts, good style..
I plan to share some of my EMC measurement tools soon also,

[Kibabalu]

link to where to order the ready made PCB's ?
or gerber download ? so we can order our self ?

no need to reinvent the wheel :-)

On Github you can find for example

https://github.com/LibreSolar/5uh-dc-lisn

The design is based on this thread. You'll find both Eagle and KiCAD files, if you want a starting point for your own modifications.

I build two of it and they are working well

[Noy]

Or look at my  Reply #94 in this thread. There are all design files for my version.
Ordered them from JLCPCB. You can use "set specific position" on order so you get the JLCJLCJLC on the front silkscreen used for JLCPCB order number stuff..

[essele]

Or look at my  Reply #94 in this thread. There are all design files for my version.
Ordered them from JLCPCB. You can use "set specific position" on order so you get the JLCJLCJLC on the front silkscreen used for JLCPCB order number stuff..

Yes ... I missed this, so have a nice "JLCJLCJLC" on the front of mine.  I never really understood why you didn't use the back silkscreen? ... it's not an extra cost, the order number can be completely hidden, and you can get all the component references on, which makes assembly much easier.

[Kibabalu]

Yes, with Noy's version you don't have to build two like me!

[Pinkus]

.....  I never really understood why you didn't use the back silkscreen? ... it's not an extra cost, the order number can be completely hidden, and you can get all the component references on, which makes assembly much easier.

I never tried that with JLCPCB - can you place the JLC order number to the bottom side? I assumed they needed all the numbers on the top to make it easier to match up the boards in a large panel.

[essele]

They have been pretty good whenever I've done any kind of front panel, without even asking they tend to put the number on the back!

Here's a shot of the front and back of the boards I had made, you can see the number tucked away underneath one of the fixing holes ... I just wished I'd spotted the JLCJLCJLCJLC on the front ;-)

[Noy]

I took green soldermask because i used my Quinsy reflow IR oven. And i was a bit frightend to use black soldermask and get burned PCBs.. And normaly green soldermask has the best / finest quality because its a liquid process and i think other colors are a kind of foil process take a look at JLCPCB capabilities site.
But you can use the color you like most.
And the bottom silkscreen is missing (thats the reason why JLCJLCJLC is on top..) because i was lazy ;-) i will build 2 LISN and Im using kicad html BOM plugin which helps a lot with interactive position light up.. so no need to do all the work of placing the silkscreen on pretty positions.

[nike75]

Hello all, Hi Noy and Jay_Diddy_B,

many thanks for great work. I am impressed with the project and I want to do it.
I looked at the gerbers files (old 27.12 and last 04.01) and noticed the following detail:
Coplanar line is provided with gap 0.4mm - not 0.2mm as discussed. When I use online calc with w=1.23mm, h=1.53mm (for 1.6mm pcb), gap 0.4mm and Er=4.5 result is 58.6 ohm.
May be I make some mistake or have a wrong clearance in PCB design.

If I use last gerbers, I need to order PCB's with thicknes of core 0.82mm for 50ohm impedance but this value will reduce mechanical strength of device.

Thanks,
Nike

[Jay_Diddy_B]

Hello all, Hi Noy and Jay_Diddy_B,

many thanks for great work. I am impressed with the project and I want to do it.
I looked at the gerbers files (old 27.12 and last 04.01) and noticed the following detail:
Coplanar line is provided with gap 0.4mm - not 0.2mm as discussed. When I use online calc with w=1.23mm, h=1.53mm (for 1.6mm pcb), gap 0.4mm and Er=4.5 result is 58.6 ohm.
May be I make some mistake or have a wrong clearance in PCB design.

If I use last gerbers, I need to order PCB's with thicknes of core 0.82mm for 50ohm impedance but this value will reduce mechanical strength of device.

Thanks,
Nike

Hi,

This was discussed in this message:

Link: https://www.eevblog.com/forum/projects/5uh-lisn-for-spectrum-analyzer-emcemi-work/msg3419946/#msg3419946

My original design was 50 .

At 100MHz and very short segments, an exact match is not required.

Use normal 1.6mm (0.062") PCB and it will work fine.

There is a very good chance that the wiring between the device under test, DUT, and the LISN is not 50 ...


Regards,

Jay_Diddy_B

[nike75]

Hi,

Certainly for these frequencies and this length the inaccuracy in the impedance will not matter much. However, I decided to adjust the layout. In order to have the least changes and keeping the shape of the polygon, I increased the tracks to 1.48mm and thus the gap is reduced to 0.275mm. According to the online calculators, this provides the required impedance.
I share a corrected gerber file.

[hydrabus]

Hi Everyone,

I have discovered this thread about LISN and it is a very amazing project and so I have created a project on GitHub to enhance actual version of the 5uH Dual LISN (I have removed the 50uH version as I do not need more than 60V / 5A for my needs and for safety reasons)
The GitHub link is https://github.com/bvernoux/5uH_LISN
The license MIT License so it is fully open
Thanks to Jay_Diddy_B & Noy for that amazing project.
Anyone is welcome to contribute on this project of course there is several tasks to dispatch but so far there is only one issue to discuss about features/improvement see https://github.com/bvernoux/5uH_LISN/issues/1
Actual versions is based on Noy version from https://www.eevblog.com/forum/projects/5uh-lisn-for-spectrum-analyzer-emcemi-work/msg3419992/#msg3419992
Modifications are mainly:

• Converted the KiCad 5.x version to KiCad 6 (5.99 Nightly) as it will be more convenient for future modifications especially for some specific plugins/features for RF stuff
• Removed the 50uH version with cleanup of the PCB
• Added full BOM (Work In Progress/To be checked/Optimized) with all parts which can generate a full BOM with KiCost

Best Regards,
Benjamin

[matbob]

Hello All,

Thanks to Jay_Diddy_B & Noy.

I have made these modifications to the layout:

1) Corrected the trace widths for 50 ohm impedance.
2) The spacing between +/GND and -/GND banana jacks has been changed to standard value of 0.75" (19.06 mm).
3) "JLCJLCJLCJLC" moved to bottom side of the PCB.

Regards,
Mathews

Edit: Replaced the 5uH_LISN.zip file. Originally had wrong Gerber files inside.

[HallWu]

Hi Bart and the group,

Did you have any issue with the cored inductors rather than air?
was your line lisn 110 or 230V?
Regards
Bart

The inductance of the inductors is not super critical. Ideally the LISN should look like 50 Ohms to the input. The impedance of the 50 uH is 314j Ohms at 1 MHz.

Here are some pictures of my LISN








I did a measurement of the input impedance using an HP 3577A Network analyzer with a s-parameter test set. One of the challenges connecting the power connector to a coax cable. (Where is my precision N to power connector adapter?)



The return loss is 23 dB at 30 MHz



This is a picture of insertion loss. Ideally it would -10db and flat. It is hard to normalize this measurement because the power connectors are not very good at 50 MHz 



Since this is used for pre-compliance testing, you compare the results against the results from the lab.

Regards,

Jay_Diddy_B

Hi Thanks for all the information.

I am trying to design a 5uH LISN based on your works which suitable for DC 200V situation. What should i notice when i choice the compoents and design the pcb ? I have browsed many scheme in the internet which based on your work, such as Wurth and LINEAR, the maximum input voltage is 60V. What should i do to improve the input voltage to 200V. Look forward to your reply.

Best Regard,
Hall.

[TimNJ]

Hi Thanks for all the information.

I am trying to design a 5uH LISN based on your works which suitable for DC 200V situation. What should i notice when i choice the compoents and design the pcb ? I have browsed many scheme in the internet which based on your work, such as Wurth and LINEAR, the maximum input voltage is 60V. What should i do to improve the input voltage to 200V. Look forward to your reply.

Best Regard,
Hall.

The voltage rating is mainly related to:

1. Voltage rating capacitors across AC or DC power rail
2. PCB spacing

For capacitors across the rail, instead of 100V rating, suggest >500V, especially if you are connecting directly to mains. You can consider using X2 or Y2 safety types, or a 630 - 1000V rated normal film type.

For PCB spacing, spacing between line and neutral and between line/neutral to earth should be increased. A rather conservative value is around 7-8mm.

You should also consider adding a bleeder resistor (with proper power rating) across the input capacitors because 200V is quite a bit more painful/dangerous than 60V.  If using with mains, add some fuses.

[HallWu]

Hi Thanks for all the information.

I am trying to design a 5uH LISN based on your works which suitable for DC 200V situation. What should i notice when i choice the compoents and design the pcb ? I have browsed many scheme in the internet which based on your work, such as Wurth and LINEAR, the maximum input voltage is 60V. What should i do to improve the input voltage to 200V. Look forward to your reply.

Best Regard,
Hall.

The voltage rating is mainly related to:

1. Voltage rating capacitors across AC or DC power rail
2. PCB spacing

For capacitors across the rail, instead of 100V rating, suggest >500V, especially if you are connecting directly to mains. You can consider using X2 or Y2 safety types, or a 630 - 1000V rated normal film type.

For PCB spacing, spacing between line and neutral and between line/neutral to earth should be increased. A rather conservative value is around 7-8mm.

You should also consider adding a bleeder resistor (with proper power rating) across the input capacitors because 200V is quite a bit more painful/dangerous than 60V.  If using with mains, add some fuses.

Hello TimNJ,

Thanks for your advice, that helps a lots. I have another questions as follows:

1. Could I use the inductance 744314110 when the Maximum DUT Current no more than 10A, no matter how high the input voltage is?
2. Where should I add the bleeder resistor? Parallel with the input capacitors such as C4 and C5 in the picture? What is the recommended resistance value of the bleeder resistor?
3. Whether the withstand voltage value of the components in the 10dB attenuator needs to be adjusted according to the change of the input voltage?

Look forward to hear from you.
Best Regard,
Hall

[TimNJ]

Hi Thanks for all the information.

I am trying to design a 5uH LISN based on your works which suitable for DC 200V situation. What should i notice when i choice the compoents and design the pcb ? I have browsed many scheme in the internet which based on your work, such as Wurth and LINEAR, the maximum input voltage is 60V. What should i do to improve the input voltage to 200V. Look forward to your reply.

Best Regard,
Hall.

The voltage rating is mainly related to:

1. Voltage rating capacitors across AC or DC power rail
2. PCB spacing

For capacitors across the rail, instead of 100V rating, suggest >500V, especially if you are connecting directly to mains. You can consider using X2 or Y2 safety types, or a 630 - 1000V rated normal film type.

For PCB spacing, spacing between line and neutral and between line/neutral to earth should be increased. A rather conservative value is around 7-8mm.

You should also consider adding a bleeder resistor (with proper power rating) across the input capacitors because 200V is quite a bit more painful/dangerous than 60V.  If using with mains, add some fuses.

Hello TimNJ,

Thanks for your advice, that helps a lots. I have another questions as follows:

1. Could I use the inductance 744314110 when the Maximum DUT Current no more than 10A, no matter how high the input voltage is?
2. Where should I add the bleeder resistor? Parallel with the input capacitors such as C4 and C5 in the picture? What is the recommended resistance value of the bleeder resistor?
3. Whether the withstand voltage value of the components in the 10dB attenuator needs to be adjusted according to the change of the input voltage?

Look forward to hear from you.
Best Regard,
Hall

The inductors will not have much voltage across them. The voltage across the inductors is only caused by the DC resistance of the wire and some voltage related to V = L * di/dt. Generally, voltage breakdown (turn-to-turn) of inductors is unlikely, unless you are working with high voltages (>1KV), with something like a CRT flyback transformer. Don't worry about these inductors @ 200V.

Do you plan to use this LISN with AC? If yes, then do not use a polarized (electrolytic) capacitor for C5. Use a film type (polypropylene) instead. (The large blue/green capacitors in JayDiddyB's post above.) Depending on the standard, usually this capacitor must be 1-10uF, or thereabouts. This capacitors (or group of capacitors) should be rated 630V - 1000V, or use a X2/Y2 class capacitor(s).

The -10dB attenuator does not need to be modified, but C3/C6's voltage rating needs to be increased to work with mains. In the above photo, you can see 100nF film capacitor (probably rated 630V or 1000V). Most of the voltage is  across C3/36, and only a small voltage is developed across R5/R13.

Add the bleeder resistors across C4/C5, yes. You can set the bleeder resistor to any value you want, depending on how quickly you want to discharge the capacitors C4 and C5. http://www.learningaboutelectronics.com/Articles/Capacitor-discharge-calculator.php. Lower value of discharge resistor means faster discharge, but the power dissipation during normal operation will be higher. Suggest a power rating at least 2x the calculated power dissipation @ 200V/240V.

[HallWu]

Hi Thanks for all the information.

I am trying to design a 5uH LISN based on your works which suitable for DC 200V situation. What should i notice when i choice the compoents and design the pcb ? I have browsed many scheme in the internet which based on your work, such as Wurth and LINEAR, the maximum input voltage is 60V. What should i do to improve the input voltage to 200V. Look forward to your reply.

Best Regard,
Hall.

The voltage rating is mainly related to:

1. Voltage rating capacitors across AC or DC power rail
2. PCB spacing

For capacitors across the rail, instead of 100V rating, suggest >500V, especially if you are connecting directly to mains. You can consider using X2 or Y2 safety types, or a 630 - 1000V rated normal film type.

For PCB spacing, spacing between line and neutral and between line/neutral to earth should be increased. A rather conservative value is around 7-8mm.

You should also consider adding a bleeder resistor (with proper power rating) across the input capacitors because 200V is quite a bit more painful/dangerous than 60V.  If using with mains, add some fuses.

Hello TimNJ,

Thanks for your advice, that helps a lots. I have another questions as follows:

1. Could I use the inductance 744314110 when the Maximum DUT Current no more than 10A, no matter how high the input voltage is?
2. Where should I add the bleeder resistor? Parallel with the input capacitors such as C4 and C5 in the picture? What is the recommended resistance value of the bleeder resistor?
3. Whether the withstand voltage value of the components in the 10dB attenuator needs to be adjusted according to the change of the input voltage?

Look forward to hear from you.
Best Regard,
Hall

The inductors will not have much voltage across them. The voltage across the inductors is only caused by the DC resistance of the wire and some voltage related to V = L * di/dt. Generally, voltage breakdown (turn-to-turn) of inductors is unlikely, unless you are working with high voltages (>1KV), with something like a CRT flyback transformer. Don't worry about these inductors @ 200V.

Do you plan to use this LISN with AC? If yes, then do not use a polarized (electrolytic) capacitor for C5. Use a film type (polypropylene) instead. (The large blue/green capacitors in JayDiddyB's post above.) Depending on the standard, usually this capacitor must be 1-10uF, or thereabouts. This capacitors (or group of capacitors) should be rated 630V - 1000V, or use a X2/Y2 class capacitor(s).

The -10dB attenuator does not need to be modified, but C3/C6's voltage rating needs to be increased to work with mains. In the above photo, you can see 100nF film capacitor (probably rated 630V or 1000V). Most of the voltage is  across C3/36, and only a small voltage is developed across R5/R13.

Add the bleeder resistors across C4/C5, yes. You can set the bleeder resistor to any value you want, depending on how quickly you want to discharge the capacitors C4 and C5. http://www.learningaboutelectronics.com/Articles/Capacitor-discharge-calculator.php. Lower value of discharge resistor means faster discharge, but the power dissipation during normal operation will be higher. Suggest a power rating at least 2x the calculated power dissipation @ 200V/240V.

Hello TimNJ,

Thanks a lot for your excellent advice . I will start my design based on your advice. Looking forward to a good result.

Best Regard,
Hall

[uski]

Hi,

Hello All,

Thanks to Jay_Diddy_B & Noy.

I have made these modifications to the layout:

1) Corrected the trace widths for 50 ohm impedance.
2) The spacing between +/GND and -/GND banana jacks has been changed to standard value of 0.75" (19.06 mm).
3) "JLCJLCJLCJLC" moved to bottom side of the PCB.

Regards,
Mathews

I was considering building this.
However, it seems like the Gerber files are from the previous, unmodified version.

Can you please upload the modified gerber files?

[EDIT] I was able to export the Gerber files from Kicad. No guarantees. See attached file. Thanks!

Thanks!

[Jay_Diddy_B]

Hi,

I viewed the gerber files provided in the previous message. This is what I found:







The banana plugs have 19.05mm 3/4 inch spacing.

They look reasonable.

Jay_Diddy_B

[uski]

Thanks for looking. I am ordered a few PCBs from JLCPCB, and a whole bunch of parts from DigiKey. I am going to build one.

What abou the 50uH version? I am confused, what is it used for? I thought the 50uH LISN were line voltage LISN, and this 60V LISN can't do it. Right? What am I missing? What is the purpose of having a 50uH version of this small LISN?

I do have 2 LISN of the "original" design by Jay_Diddy_B (thank you!!!) that I used successfully in the past (thank you!!! saved my ass during precompliance testing), but I like the "all in one" version.

[T3sl4co1l]

You probably wouldn't want to apply line voltage to that, given the clearances, yeah.  Inductors that size won't have great saturation current, either.  But you could still use it for 24VAC things I suppose, if that was ever a need?...

Probably not a lot of things running at low voltage, that would still be useful to know their response at lower frequencies (10s instead of 100s kHz cutoff), but regardless of applicable standards, that's simply the effect, so, whatever you make of it.

Oh also, for posterity, I should link this high current LISN I made: https://www.eevblog.com/forum/projects/high-current-lisn/msg4576645/#msg4576645 No PCB designs, it's just bits soldered/glued together anyway, obvious enough.  Capacitors rated 400V so it could potentially be used for quite some power.

Tim

[Smokey]

...
Will upload the design files for CM/DM seperator in the other thread..

Did you ever end up making that CM/DM separator?  How did it work?

Note:  Probably this thread: https://www.eevblog.com/forum/projects/diy-dm-cm-seperator-for-emc-lisn-mate

[Smokey]

I'm looking at making one of these dual 5uH LISNs...

I read through the thread and I didn't see anyone with any numbers on how much it actually costs to make one of these... so..

Based on the files in this post by matbob: https://www.eevblog.com/forum/projects/5uh-lisn-for-spectrum-analyzer-emcemi-work/msg3789893/#msg3789893

10 PCBs from PCBWay, with shipping = $36USD
BOM at Digikey (1 set of parts, no shipping) = $75USD

So, as of right now, about $125USD to make one dual 5uH LISN.

[Smokey]

Thanks for looking. I am ordered a few PCBs from JLCPCB, and a whole bunch of parts from DigiKey. I am going to build one.

What abou the 50uH version? I am confused, what is it used for? I thought the 50uH LISN were line voltage LISN, and this 60V LISN can't do it. Right? What am I missing? What is the purpose of having a 50uH version of this small LISN?

I do have 2 LISN of the "original" design by Jay_Diddy_B (thank you!!!) that I used successfully in the past (thank you!!! saved my ass during precompliance testing), but I like the "all in one" version.

There is another whole thread about 50uH LISN:
https://www.eevblog.com/forum/rf-microwave/50uh-and-250uh-inductor-design-for-lisn/