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 probe
Since 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.
Great, 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, RG223
I 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.