I have been asked to investigate an issue of Interpolation of CREEPAGE AND CLEARANCE regarding the ratings of handheld multimeters. Clause D.2 of IEC 1010-1 (and the harmonized equivalents; ANSI/ISA S82.01-1994, CAN/CSA C22.2 No. 1010-1: 1992 and EN 61010-1:1993) sets forth the CREEPAGE and CLEARANCE determination requirements if the working voltage is up to 1000 V and if installation categories (overvoltage categories) are applicable. This includes the ratings of most handheld DMM's. Clause D.2.1 points to the applicable tables for BASIC or DOUBLE INSULATION and INSTALLATION CATEGORY according to annex J. Clause D2.2 "Application of Tables D.1 to D.12" allows interpolation of CLEARANCE only for a circuit or part which has now direct connection to the mains supply...". It further requires CREEPAGE DISTANCE to always be at least as large as the value specified for CLEARANCE.
This seems to say that the rating for any product that directly connects to the mains supply must be at one of the incremental voltages (50,100,150,300,600,1000) listed in Tables D.1 thru D.12. I have polled CSA's Vancouver BC office, TUV Product Services in San Diego and UL's Primary UL 3111 engineer in Melville. So far (with the exception of UL, whose response is under consideration and review by UL) the response has been consistant with the above paragraph. Here's the question for the experts at the agencies (UL, TUV, VDE, CSA and others), or elsewhere: Is it possible within the bounds of IEC 1010-1 to rate a handheld DMM for example at 750 V and interpolate the CREEPAGE and CLEARANCES in spite of the above ? Thanks in advance for your comments, Best regards, Dan Teninty P.E. Senior Design Engineer Product Safety [email protected] FLUKE Corporation Everett, Washington (206) 356-6035 (206) 356-6490 fax
