Conducted immunity and emissions with home made equipment (EMC)

[Gabriel Sá Pinto]

Hello there.
I'm not sure if EMC compliance fits in this category, but I couldn't find a better one, in case there's a better one please relocate me.

Currently, in my job, I'm trying to make an EMC test plan for our product, that is Conducted and Radiated Emissions and Immunity.
The problem lies with the equipment used in Conducted testing, professional current probes and transformers for monitoring and injection are quite an expensive purchase for something we won't use that often.

So I was wondering if there's a cheaper way of building our own probes with sufficient injection and monitoring capability.
We already have a LISN (TEKBOX TBOH01 5uF), and we've measured some emissions with it and I also know it's possible to inject power with it, the thing is how much and if it's enough. Also the standard specifies we have to separate Common mode from Differential mode, and for what I've seen online that's not possible without a current probe.

I'll attach the standard we're following, and I'll write down some of the specifications that were provided by our contractor:

CS on power leads – Sine Wave Injection – Differential Mode
- Vinjection = 1 VRMS, 9 kHz to 50KHz
- Vinjection = 1 VRMS, 50KHz to 50MHz, with a 50% AM envelope modulation 1 KHz square wave.

CS on power leads – Sine Wave Injection – Common Mode
Vinjection = 1 VRMS, range from 50kHz to 50MHz, 50% AM envelop modulation 1 KHz square wave.

CS on signal lines – Sine Wave – Common Mode
Subject the unit to the following “Bulk” CM sinusoidal injection superimposed on the signal interface lines:
P incident limited to 1W/50Ω (CW):
- Iinjection = 86 dBμArms,
- Frequency range: 50kHz - 50MHz
- Modulation: 1 kHz pulse repetition rate, 50% duty cycle

As for monitoring emissions, the frequencies vary from around 30Hz to 100MHz, but what's really important is between 10kHz and 50MHz
​

We have no experience in this area so any help would be appreciated, in the meantime I'll be making some research and updating accordingly.
Thanks in advance,

Best regards,
Gabriel

 

[AnalogKid]

A certified testing lab, with the right equipment, calibration records, and trained personnel, charges thousands of dollars (US) for this kind of work because these are expensive tests. Just doing the testing is hard enough, but maintaining the equipment and the records to prove that the results are accurate is a continuous process that is a large expense of its own. Unless your company is going to be testing products about once a month, it just isn't worth it to bring the entire process in-house.

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