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I'm trying to improve my understanding of the CISPR 14.1 EMC test procedures and requirements, with a view to performing precompliance testing. In particular, I'm looking at conducted emissions measurements.

My understanding is that conducted emissions measurements are applied only to mains cables, but reading CISPR 14.1 I'm unable to confirm that this is the case.

Measurements in the 150kHz to 30MHz range are made on terminals:

Terminals are defined as conductive parts, suitable for re-usable electrical connection to external circuits

which I understand to also refers to connectors, not just terminal blocks.

There are additional stipulations as to which terminals the limits apply to, which in addition to the obvious mains supply terminals are:

On additional terminals of appliances as well as on load and additional terminals of regulating controls incorporating semiconductor devices the relaxed limits given for "additional terminals" in columns 4 and 5 apply.

No terminal voltage limits apply for leads, which are not easily extensible by the user (permanently connected, or provided with a specific connector), which are shorter than 2 m, and which connect the equipment with an auxiliary apparatus or device, (e.g. semiconductor speed controls, power plugs with AC-DC converters).

Our device has a 12VDC solenoid mounted externally, connected by a specific connector and 1.5m length of cable, but I don't think that the solenoid would be classified as an "auxiliary apparatus", which would indicate that it would require testing. Edit: here's a block diagram/simplified schematic. There are some electronics running off the 12VDC too which control the relays.

Block diagram

I've searched for other CISPR 14.1 test reports to compare to but none that I can find have any more terminals than just the power supply.

So what terminals/connections/cables does one actually apply conducted emissions testing to?

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  • \$\begingroup\$ Can you show the relay connection with a block diagram and/or schematic? \$\endgroup\$ – winny Apr 13 '18 at 8:02
  • \$\begingroup\$ I've updated as requested. \$\endgroup\$ – Zac Soden Apr 15 '18 at 23:33
  • \$\begingroup\$ Tricky case. Is it user connectable? \$\endgroup\$ – winny Apr 16 '18 at 9:21
  • \$\begingroup\$ Yes, and with bare leads at that, which means that the user could very easily extend them and therefore the standard would not exclude them, despite being less than 2m. \$\endgroup\$ – Zac Soden Apr 16 '18 at 21:09
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I try to share my knowledge with you, but I do not have references for this and I might be false on some topics:

First of all, you need to know how long the cables to your terminals are (not only mains, but all terminals). If its longer than 30 meters, then you have to do surge testing (lightning stroke tests), burst tests and of course conducted emission/immunity. If the cable of a port is between 3 and 30 meters, you can skip the surge tests. If a port has a cable <3m, you do not need any test (except ESD). Mains supply always needs full testing (because the lenght could be >30m).

So from my point of view, your solenoid does not need conducted testing, because the cable is <3m. But the other terminals need testing.

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  • \$\begingroup\$ Thanks Stefan. That sounds like you're referring mainly to CISPR 14.2 (immunity), rather than 14.1 (emissions). As I quoted, 14.1 actually discusses cable lengths being under 2m, but it's the teram "auxiliary apparatus" that has me questioning. \$\endgroup\$ – Zac Soden Apr 16 '18 at 6:01
  • \$\begingroup\$ I would also agree with you that this 1.5m solenoid is not considered as an external apparatus. It just has no emission potential, because the lambda/4 antenna for a 30MHz signal would be ~2.5 meters long. \$\endgroup\$ – Stefan Wyss Apr 16 '18 at 10:13
  • \$\begingroup\$ That's true, but the standard does explicitly state "not easily extensible", which in this case is not true. So I would perform voltage tests on these terminals using a voltage probe? \$\endgroup\$ – Zac Soden Apr 16 '18 at 21:12

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