Rick, UL defines CTI as "the voltage which causes tracking after 50 drops of 0.1 percent ammonium chloride solution have fallen on the material. The results of testing the nominal 3mm thickness are considered representative of the material's performance in any thickness." Thanks SGour
-----Original Message----- From: Rick Busche [SMTP:[email protected]] Sent: Thursday, February 19, 1998 12:23 PM To: [email protected] Subject: Comparative Tracking Index IEC 950 defines CIT (comparative tracking index) in terms of material groups for the determination of creapage distance. Specifically groups I, II, IIIa and IIIb. are mentioned. In paragraph 2.9.3 (note 3) the actual index (CTI) is referred to as <600 or <400. My questions are as follows: 1. Is this CTI (as assigned by UL in the yellow book) actually a voltage level? 2. The FR4 laminate we use has been rated at 205. As such the maximum creapage distance is mandated. Is it common to find better material? Is this 205 level typical of common FR4 materials? Thanks Rick Busche Evans & Sutherland [email protected]
