Frank, I we limit the discussion to the measuring instrument circuit found in Figure D.1 of EN 60950, you see a relatively large capacitance on the input of the circuit followed by a little resistance and a rectifier bridge. The "meter" is then described as a 0 mA - 1 mA moving coil movement. I estimate that the circuit begins to roll-off at about 700 Hz, but there is one sensitivity check at 5 kHz. I would guess that the Simpson can perform at least as well as this.
This circuit does not employ the traditional Volt-Ohm Meter (VOM) device that folks sometimes confuse with an analog meter movement. My understanding is that the intent is to only measure "line frequency" related leakage current and it really shouldn't matter. Other standards (e.g. EN61010) take into consideration the higher frequencies and even RF frequencies but for the most part the industrial and commercial equipment standards do not. The difficulty I had was in convincing the inspector that a DVM was acceptable, not because of frequency response but for the aliasing problem found in some DVMs. Doug -----Original Message----- From: FRANK GOTO [mailto:[email protected]] Sent: Wednesday, March 17, 1999 5:00 PM To: [email protected] Subject: RE: Leakage Current Measurements Interesting. During an audit of the facilities of a former employer, the auditor specifically requested that we didn't use the Simpson 228 for EN60950 because of the roll-off of the analog movement above 100Hz. The suggested fix was to build the network as described in the standard, with a high frequency true RMS digital meter. Frank F. Goto ------------- Original Text From: "POWELL, DOUG" <[email protected]>, on 3/17/99 12:58 PM: Peter, We use a fixture described in the EN 60950, IEC 61010 or EN50178 standards along with an analog meter movement, as described in the standard. The reason for the analog meter, according to the inspector is that many of the digital meters have an aliasing problem at low frequencies. However in the last few years he/they have been accepting the readings of any digital meter with "true RMS" capability, owing to the fact that many of the commercial systems are also not digital. So far this approach has worked just fine for the LGA Nurnberg and CSA. ================================== Doug Powell, Compliance Engineer Advanced Energy Industries, Inc. Fort Collins, Colorado USA [email protected] www.advanced-energy.com ================================== --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
