A bare CTI number can be read wrong. “CTI 400” looks like a clean result until you learn it was run with the aggressive contaminant, or that the 100-drop figure sat 50 V lower, or that erosion ate 3 mm off the specimen while it passed. All of that lives in the report — and a compliant report… Read More: How to Read a CTI and Tracking Test Report »
The specimen decides the number almost as much as the material does. A tracking test measures how a surface behaves under a contaminated film, and nearly every rule about how you cut, clean, and condition that surface exists to stop the specimen itself from becoming the variable. Get the prep wrong and the result is not slightly off… Read More: CTI Test Specimen Preparation Guide (IEC 60112 & 60587) »
A datasheet quotes “CTI 400V, PLC 1, Material Group II” and an engineer new to the part assumes those are three separate properties. They are not. They are one measurement — surface tracking resistance — expressed in three different bookkeeping systems, because three different bodies standardized the same drop test. Knowing which system a number came from matters,… Read More: IEC 60112 vs ASTM D3638 vs UL 746A: CTI Standards »
The single most important thing to know before you use any CTI table: the number belongs to a grade, not a material family. Two compounds both labeled “PBT” can sit in different material groups because one has a flame-retardant package and a filler tuned for tracking and the other does not. Every value below is indicative — a… Read More: CTI Values of Common Insulating Plastics (with Table) »
Insulating material does not have to break down through its bulk to fail. It can fail across its face. A thin film of dirty water, a few hundred volts, and enough time will burn a conductive path into a plastic surface that measured hundreds of megohms when it was clean. That path is called a track. IEC 60112… Read More: Comparative Tracking Index (CTI): IEC 60112 Test Method Explained »