Electrical connectors are widely used in many kinds of main equipment. It is very difficult, costly, and time consuming for the off-line diagnosis of intermittent faults (IFs) in connectors. To realize the on-line diagnosis by the traditional method, the voltage drop between two ends of the connector should be measured continuously at a high sample rate. This continuous measurement requires enormous testing resources, which is impractical in engineering fields. To solve this problem, this paper proposes an on-line diagnosis method in condition of the single-end test for the electrical connector IFs. To determine the fault threshold of the electrical contact resistance (ECR), first the impact of the ECR on high-speed transmission is studied, and then the connector fault feature in condition of the single-end test, which is called the insertion loss increment (ILI), is extracted. The measurement method of the ILI is also presented. Based on the above analysis, an ILI-based on-line diagnosis method for the connector IFs is specified. According to the qualitative and quantitative tests, the proposed diagnosis method is verified. The verification results show that the cumulative insertion loss increment, which is calculated from the ILI can truly exhibit the variation of ECR, and the error of the ILI-based diagnosis method is only about 1%.
