All, We've run across a customer requirement which includes testing to paragraphs 4.9.1 and 4.9.2 of ETS 300 132-2. We've had a problem with this test. I've searched around on and off for a couple of days for a solution. I know that the guys at the lab follow this group, but now I must swallow my pride and seek the knowledge of the all-knowing benefactors who sub-scribe to the group.
Never tested a product to this standard before. For those unfamiliar with the standard, these two paragraphs specify what appears to be a differential mode conducted emissions measurement for 48VDC powered equipment. Section 4.9.1 deals with a narrow band emission measurement from 25Hz to 20KHz using a spectrum analyzer with a 10Hz bandwidth (from 25Hz to 10KHz) and a 200Hz bandwidth (from 10Khz to 20Khz). Section 4.9.2 deals with a wideband emission done in two parts. The first part is a psophometrically (never knew what a psophometer was until now) weighted average from 25Hz to 5Khz. The second part is a flat (unweighted) average from 5KHz to 20KHz. All measurements are performed with a unique LISN circuit specified in the standard. So what's my question? Well, we inevitably failed the psophometer test (wideband 25Hz to 5Khz). Our system has no power supplies switching within this frequency range. What types of noise sources within a typical power supply or product would produce emissions in this frequency range? I've considered transformer "buzzing". Is this it? I've been looking at filter suppliers. Most of my old stand-by's produce filters designed for higher frequencies. Are there any vendors who deal with this type of low frequency filtering? Any other words of wisdom from those who have previously undergone this test? Thanks, Chris Maxwell, Design Engineer GN Nettest Optical Division 6 Rhoads Drive, Building 4 Utica, NY 13502 PH: 315-797-4449 FAX: 315-797-8024 EMAIL: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
