Pre-Compliance Setup - Page 1
Forum section: electronics / testgear

author: kylehunter
author_rank: Regular Contributor
timestamp: June 02, 2021, 11:09:45 pm
content: Heya guys,My company is looking to get a low-end pre compliance setup for EMC testing. Boards will all be DC, so no issues with mains testing for conducted emissions. Majority of our work is fairly low-speed as well, with the major noise sources being buck/boosts, and inductive load switching. I'm mostly looking into Tekbox for their LISN for conducted, current clamps for common-mode emissions, and near-field probes for comparison of design changes. Potentially down the road get a shielded tent for some low-grade far field testing, but I'm keeping my expectations realistic, so likely that will not happen.Budget for everything should be < $5K. I've been looking into a Siglent SSA3021X-TG, Rigol DSA815-TG, or a Tek RSA306. I really do like the idea of having a tracking gen built in, so the RSA306 doesn't seem like a great fit. My main concern is, how big of a difference are the super budget < $2K SA's vs the < $5Ks? Realistically, this setup will just be to get our feet wet in this realm, and likely would upgrade with a much larger budget down the road. So if it is just a marginal performance buff to go from the Rigol/Siglent to something a bit more expensive, that likely won't make sense.Any other advice/input is much appreciated! Planning on starting doing pre-compliance based on these docshttps://emcfastpass.com/current-probe-e-field-emi-testing/andhttps://download.tek.com/document/37A_60141_1_HR_Letter.pdf

author: tautech
author_rank: Super Contributor
timestamp: June 02, 2021, 11:18:20 pm
content: SSA3015X Plus is ideal for this with the EMI package (option and NF probe set) on promotion with any SSA/SVA new purchase.https://siglentna.com/news-article/a-new-bundle-for-emi-pre-compliance-test/However for general SA work the SSA3021X Plus has better specs.Carefully check the datasheet.https://siglentna.com/download/15114/

author: kylehunter
author_rank: Regular Contributor
timestamp: June 03, 2021, 12:32:37 am
content: Quote from: tautech on June 02, 2021, 11:18:20 pmWoah, that package is a sweet deal!What makes you say that the SSA3015X is a better fit for EMC testing? I looked through the datasheet and spec for spec the 3021 appears to beat it.

author: tautech
author_rank: Super Contributor
timestamp: June 03, 2021, 12:47:32 am
content: Quote from: kylehunter on June 03, 2021, 12:32:37 amEMI work is typically LF so well within the range of SSA3015X Plus and if EMI is your primary use there is little to be gained from the more expensive SSA3021X Plus however for general SA work it is better and particularly its TG spec.

author: kylehunter
author_rank: Regular Contributor
timestamp: June 03, 2021, 01:10:34 am
content: Quote from: tautech on June 03, 2021, 12:47:32 amAhh now that makes total sense. I thought there was something for EMC that made the 3015 better. I do see the need for us to use the TG, so I think it's worth it for us to spend the extra.

author: tautech
author_rank: Super Contributor
timestamp: June 03, 2021, 01:35:47 am
content: Yes those that have some idea of their future SA needs prefer the SSA3021X Plus.For EMC all these Siglent SSA/SVA's have the same EMI option and within its UI EMI testing is broken into a # of standard bands where thresholds for each can be set depending on your local requirements or if you intend to market your products worldwide.Each and every option has 120hrs of instrument runtime before their specialist functionality ceases and licenses need be purchased or hacked.I know with my SVA1032X some considerable work was done with it before the option time remaining got low when I had to do something about it.Lots of SSA, SSA+ and SVA info here on the forum for you to wade through.

author: kylehunter
author_rank: Regular Contributor
timestamp: June 03, 2021, 10:36:42 pm
content: Quote from: tautech on June 03, 2021, 01:35:47 amAwesome, thanks for the advice!

author: fourfathom
author_rank: Super Contributor
timestamp: June 03, 2021, 10:55:47 pm
content: Quote from: kylehunter on June 02, 2021, 11:09:45 pmDo you really need a shielded tent?I used to do FCC EMI testing at 3 and 30 meters, and we often used open-field test sites. For pre-compliance or self-certification (used to be called Verification) I used a nearby grassy field, or at one company we had a large area of wire mesh under an asphalt top in our parking lot. For formal certification I've used commercial open-field sites, and one time a large anechoic chamber.

author: kylehunter
author_rank: Regular Contributor
timestamp: June 04, 2021, 10:53:31 am
content: Quote from: fourfathom on June 03, 2021, 10:55:47 pmYeah, that's a good point. Like I said, won't be worrying about that till later on anyway.

author: Feynman
author_rank: Regular Contributor
timestamp: June 05, 2021, 09:23:18 am
content: A pre-compliance setup generally depends on what tests your products typically fail at in a certified lab.But I think your choice of equipment makes total sense, as far as I can tell. One of the most useful pre-compliance measurements is common mode current on cables with a current clamp. This gives a good indication for radiated emissions. You can also hook up a signal generator to you current clamp and simulate cable pick-up in a radiated immunity test. But you'll need a signal generator with a decent amount of output power and with the capability for 1kHz 80% AM modulation. Affordable signal generators go up to about 10-20 dBm. Around 20 dBm is the sweet spot for maybe finding some weak spots in your design, without frying your current probeSince your designs are likely to contain a buck converter, a LISN setup makes total sense, too. Please keep in mind that for measuring both supply lines you'll need either two DC LISNs or one switchable AC LISN (an AC LISN can be used for DC lines as well, if you'll stay within the voltage/current ranges). When actually measuring AC lines you'll need an isolation transformer, because LISNs have large capacitors to earth, which draw enough current at 50Hz/60Hz to blow your RCD.Near field probes are a good idea, too. Maybe an (open) TEM cell would be a good addition to this, since it provides a more defined environment.

author: kylehunter
author_rank: Regular Contributor
timestamp: June 05, 2021, 01:00:40 pm
content: Quote from: Feynman on June 05, 2021, 09:23:18 amGreat, thanks for the feedback, here's what I have selected atm:- Siglent SSA3021X Plus (with the EMI promo)- EMI promo SRF5030T near field probe set- TekBox TBOH01 LISN- TekBox TBFL1 Transient Limiter / Attenuator- Instek ADB-006 DC Block N-type 50- TekBox TBCP2-500 Current Monitoring Probe- 3x TekBox NM-NM/75/RG223 N-Male to N-Male, 75 cm, RG223- TekBox NM-BNCM/75/RG223 N-Male to BNC-Male, 75 cm, RG223I would use the DC Block and Transient limiter/attenuator at all times to protect the SA.> Please keep in mind that for measuring both supply lines you'll need either two DC LISNs or one switchable AC LISN (an AC LISN can be used for DC lines as well, if you'll stay within the voltage/current ranges).Can you explain that please? We are only doing DC-DC work. My understanding is with a single LISN, you will be able to see the total gain of both diff and CM noise, just not separated. Then, using something like a TekBox TBLM01 Line Impedance Stabilization Network Mate + a second LISN, that would split CM and diff noise. Or, are you implying that this type of measurement is only useful when you can see the noise sources separated out? I can understand that if so.> A pre-compliance setup generally depends on what tests your products typically fail at in a certified lab.True. We are a design shop, so we don't have standard in-house designs, nor tests that we normally fail. So we really need to account for the widest range of possibilities.

author: Feynman
author_rank: Regular Contributor
timestamp: June 05, 2021, 04:13:34 pm
content: Quote from: kylehunter on June 05, 2021, 01:00:40 pmWhen you are required to measure both supply lines (depends on your product, i. e. the applicable standard) you still need two DC LISNs with one LISN connected to the analyzer and the other terminated into 50 Ohms. Yes, if you want to separate CM and DM noise, you'll need two LISNs as well. But that's a different topic (can be handy for trouble shooting and selecting filter types). With one DC LISN you can only measure the noise on the positive line.As for the DC block please consider its frequency response. Most dc blocks will have significant attenuation in the frequencies of interest for conducted emission tests. The ADB-006 is rated "10 MHz to 6 GHz", so I guess it'll attenuate pretty much the whole frequency rangeThe transient limiter should be good enough and has a flat response from 9 kHz to 600 MHz. Generally it's a good idea to have a DC block in front of your analyzer, of course. So I would buy it anyway.

author: tautech
author_rank: Super Contributor
timestamp: June 05, 2021, 07:36:11 pm
content: Quote from: kylehunter on June 05, 2021, 01:00:40 pmAll SSA/SVA have an internal DC block that's 50V rated.When I got my first a SSA3032X (pre Plus) I too sweated about input damage and got a DC block but TBH I've rarely ever used it with that SA or the later SVA1015X or my latest a SVA1032X.YMMVLately I've focused on SMA cabling and accessories rather than N type.

author: kylehunter
author_rank: Regular Contributor
timestamp: June 05, 2021, 08:25:18 pm
content: Quote from: Feynman on June 05, 2021, 04:13:34 pmGot it, that makes sense.Quote from: tautech on June 05, 2021, 07:36:11 pmWill remove the DC block from my list!> Lately I've focused on SMA cabling and accessories rather than N type.So, for us, since we have 0 cabling for SA's already, I was figuring since N seems to be more rugged and is on all of Tekbox's accessories, to just base it mainly off of that standard. Would you suggest otherwise?

author: tautech
author_rank: Super Contributor
timestamp: June 05, 2021, 08:38:02 pm
content: Quote from: kylehunter on June 05, 2021, 08:25:18 pmWell it's just about flexibility really as SMA cables are nicer to use. BNC cables are bad enough and N type generally worse unless you shell out real $ for top quality however in your position I'd get the bare minimum for now with a view to getting cables that better suit your needs once you get some experience with what you get. It's not like EMI work is particularly challenging on cabling as it's most quite low frequency of just a few 100 MHz.

author: charliedelta
author_rank: Regular Contributor
timestamp: June 06, 2021, 06:48:52 am
content: Also consider buying the LisnMate. Tekbox makes one. Its useful to be able to distinguish differential versus common mode interfering currents on the fly.

author: kylehunter
author_rank: Regular Contributor
timestamp: June 07, 2021, 08:03:57 pm
content: Quote from: tautech on June 05, 2021, 08:38:02 pmOh, OK. Makes sense to me!Quote from: charliedelta on June 06, 2021, 06:48:52 amYeah, I mentioned it earlier. I plan on getting it from Tekbox and another LisnMate down the road. Only saves like $50 on the package, so not a huge need to get it now.

author: tycoon_9
author_rank: Newbie
timestamp: August 22, 2021, 07:42:28 am
content: Using LISN mate or CM-DM noise separator requires 2 LISNs because ordinary LISN can output 1 signal once at a time.The better toy to debug conducted EMI is a LISN with an integrated CM-DM noise separator like this one : Cybertek EM5040B. It has CM-DM noise separator, 10dB atten, and RF limiter. I have had this one working in my home lab since Covid last year. It is a good investment.http://www.cybertek.cn/info/464

author: pisoiu
author_rank: Regular Contributor
timestamp: January 08, 2022, 08:02:37 pm
content: Hi all,Since I'm on the same boat with putting together a pre-compliance setup, I ask here instead of opening a new topic.I have more or less the same setup as above, my work is generally in automotive low power communication devices, so just dc-dc work.I have some troubles distinguishing ambient RF noise from DUT noise in TEM cells so it seems I need a shielding tent for that and also to keep RF inside when doing immunity tests.However, the ready made options available are too pricey for my taste, so I am thinking to build one.Question is: do you think conductive materials available on aliexpress are ok for the job? example:https://www.aliexpress.com/item/1005003676563617.htmlThanks.

author: knudch
author_rank: Regular Contributor
timestamp: January 09, 2022, 10:43:18 am
content: If you have problem with background noise in a TEM-cell then you don't have proper I/O filtering from the TEM-cellThe TEM-cell have much higher shielding effectiveness than such a tent.....if proper made.You will have same problems with a tent.

author: pisoiu
author_rank: Regular Contributor
timestamp: January 09, 2022, 11:41:36 am
content: I'm confused. Are you saying the cell should not pick up ambient RF without shielding? I do not see how, it is open on sides...It's the cell from the picture.